Pneumatic tire and mold for molding same

Abstract

To provide a pneumatic tire capable of suppressing the occurrence of shininess or bloom phenomenon caused by reflection of sunlight on a surface facing the outside of a block protrusion in a tire axis direction in a configuration provided with a plurality of block protrusions on a tire side surface.SOLUTION: A tire 1 comprises a plurality of block protrusions 5b protruding from a plurality of positions in a tire circumferential direction to the outside in a tire axis direction on a tire side surface 13 which is an outside surface in the tire axis direction inside the ground contact end T of a tread 10 in a tire radial direction and outside a rim line in the tire radial direction. Surface roughness is larger on the surface of the block protrusions 5b facing the outside in the tire axis direction than parts other than the block protrusions 5b on the tire side surface 13.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having a plurality of block protrusions provided on a tire side surface, which is an axially outer surface of the tire, radially inward of the ground contact edge of the tread. [Background technology]

[0002] Patent Document 1 describes providing a plurality of protrusions aligned in the tire circumferential direction on the surface of an annular region of a sidewall portion of a tire. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-119277 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a tire configuration in which multiple block protrusions are provided on the tire side surface, which is the axially outer surface of the tire radially inward of the tire tread contact edge, there is a possibility that the axially outward facing surface of the block protrusions, particularly the outer surface of the highest part, may become shiny due to reflection of sunlight. Furthermore, it is known that creating a mirror-finished tire surface can cause poor rubber flow during tire molding. Poor rubber flow leads to insufficient vulcanization, making the rubber more susceptible to damage such as cracks. This poses a problem of blooming occurring more easily from the damaged areas.

[0005] An object of the present invention is to provide a pneumatic tire and a molding die for the same, which have a configuration in which a plurality of block protrusions are provided on the tire side surface, and which can suppress shine caused by reflection of sunlight on the surfaces of the block protrusions facing outward in the tire axial direction, and can also suppress the occurrence of the bloom phenomenon. [Means for solving the problem]

[0006] The pneumatic tire according to the present invention includes a tire side surface, which is an axially outer surface of the tire, located radially inward of a ground contact edge of the tread and radially outward of a rim line, and includes a plurality of block protrusions protruding axially outward from a plurality of positions in the tire circumferential direction, The pneumatic tire has a surface roughness of the axially outward facing surfaces of the plurality of block protrusions greater than that of the tire side surface other than the plurality of block protrusions.

[0007] The mold for molding a pneumatic tire according to the present invention is a mold for molding a pneumatic tire that has a plurality of block protrusions that protrude axially outward from a plurality of positions around the tire on the tire side surface, which is the axially outer surface of the tire that is radially inward from the ground contact edge of the tread and radially outward from the rim line, and the portions that form the surfaces of the plurality of block protrusions that face axially outward have a greater surface roughness than the portions of the tire side surface that form other than the plurality of block protrusions. [Effects of the Invention]

[0008] According to the pneumatic tire and molding mold thereof of the present invention, when the resulting pneumatic tire has a configuration in which a plurality of block protrusions are provided on the tire side surface, it is possible to suppress the occurrence of shine and blooming on the surface of the block protrusions facing axially outward. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing a portion in the circumferential direction of a pneumatic tire that is an example of an embodiment. [Figure 2] FIG. 2 is a view of the upper part of the tire side surface of FIG. 1 as viewed in the tire axial direction. [Figure 3] 1 is a meridian cross section of a pneumatic tire according to an embodiment, in which block protrusions are omitted. [Figure 4] 3 is a cross-sectional view taken along the line AA in FIG. 2. [Figure 5] 1 is a cross-sectional view of a tire mold according to an embodiment. [Figure 6] FIG. 4 is a diagram showing processing conditions when a shot peening process is performed on a molding surface of a mold according to an example of an embodiment. [Figure 7A] 10 is a schematic diagram for explaining why shininess occurs on the surface of a block protrusion facing outward in the tire axial direction due to reflection of sunlight in a comparative example. FIG. [Figure 7B] 5A and 5B are schematic diagrams for explaining why shining caused by sunlight reflection can be suppressed on the surface of the block protrusion facing outward in the tire axial direction in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an example of an embodiment of a pneumatic tire and a molding die thereof according to the present invention will be described in detail with reference to the drawings. The embodiment described below is merely an example, and the present invention is not limited to the following embodiment. Furthermore, the present invention includes selective combinations of the respective components of the multiple embodiments and modified examples described below.

[0011] Fig. 1 is a perspective view showing a circumferential portion of a pneumatic tire 1 according to an embodiment. Fig. 2 is a view of the upper portion of a tire side surface 13 in Fig. 1 as viewed in the tire axial direction. Fig. 3 is a view of a meridian cross section of the pneumatic tire 1 according to an embodiment, with block protrusions omitted. Hereinafter, "pneumatic tire 1" will be referred to as "tire 1."

[0012] The tire 1 has a tread 10, which is the portion that comes into contact with the road surface. The tread 10 has a tread pattern including a plurality of blocks such as shoulder blocks 2a, 2b, and is formed in an annular shape along the tire circumferential direction. A plurality of grooves 2c, 2d that separate the blocks are formed in the tread 10. The tread 10 has a ground contact edge T. In FIG. 2 , X1 indicates a first direction in the tire circumferential direction, X2 indicates a second direction in the tire circumferential direction, Y1 indicates an outer side in the tire radial direction, and Y2 indicates an inner side in the tire radial direction.

[0013] The following description will focus on the outer side (OUT side) of the vehicle with respect to the axial center of the tire as the configuration of the tire 1. The outer side and inner side of the tire 1 are symmetrical.

[0014] The tire 1 includes a sidewall 5, which is provided at the axially outer end of the tread 10 and bulges outward most in the axial direction of the tire, and a bead 14 (FIG. 3) fixed to the rim of a wheel. The sidewall 5 and the bead 14 are formed in an annular shape along the circumferential direction of the tire. The sidewall 5 extends radially inward from both axial ends of the tread 10. As shown in FIG. 3, a rim strip 18, which forms the outer surface of the bead 14, is provided adjacent to the sidewall 5 at the radially inner end of the tire 1.

[0015] The tire 1 is a pneumatic tire filled with air at a predetermined pressure. The tread 10 is made of tread rubber. The sidewall 5 is made of a different type of sidewall rubber than the tread rubber.

[0016] In this specification, unless otherwise specified, the dimensions of each part of a tire are dimensions measured when an unused tire is mounted on a standard rim, inflated to the standard internal pressure, and in a standard, unloaded state.

[0017] "Touching edge T" refers to both ends in the axial direction X of the tire in the area that comes into contact with a flat road surface when an unused tire 1 is mounted on a standard rim, inflated to the standard internal pressure, and subjected to a load that is 88% of the standard load at the standard internal pressure.

[0018] Here, a "regular rim" is a rim specified by the tire standard, and is a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. "Regular internal pressure" is the "maximum air pressure" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "INFLATION PRESSURE" for ETRTO. "Regular load" is the "maximum load capacity" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "LOAD CAPACITY" for ETRTO.

[0019] As shown in FIG. 3 , the tire 1 includes a carcass 19 and a belt layer 20. The carcass 19 is a cord layer coated with rubber and forms the framework of the tire 1, which can withstand loads, impacts, air pressure, etc. The belt layer 20 is a reinforcing band disposed between the tread rubber and the carcass 19. The belt layer 20 tightens the carcass 19 to increase the rigidity of the tire 1. The belt layer 20 is formed by overlapping, in the tire radial direction Y, small-width belts 21 and large-width belts 22, which are multiple belts and are disposed radially outward of the small-width belts 21 and are longer in the tire axial direction Z than the small-width belts 21. Each of the belts 21, 22 is formed by covering, with rubber, multiple cords arranged in a direction inclined relative to the tire circumferential direction. The cords of adjacent belts 21, 22 are inclined in opposite directions relative to the tire circumferential direction so that they cross each other. The cords are formed from steel or the like.

[0020] A belt reinforcing layer (not shown) is provided between the belt layer 20 and the tread rubber, extending in the tire circumferential direction and covering the entire belt layer 20 in the tire axial direction Z. The belt reinforcing layer is formed by covering cords extending substantially in the tire circumferential direction with rubber. The cords are made of organic fibers or the like.

[0021] Furthermore, a rim protector 23 that protrudes axially outward is provided as part of the rim strip rubber that forms the rim strip 18. The rim line 24 is provided in an annular shape along the circumferential direction of the tire at the apex located at the axially outer end of the rim protector 23. The rim protector 23 has the function of protecting the rim from external damage. The rim line 24 is a line that can be used to check the gap between the tire 1 and the rim to ensure that the tire 1 is properly mounted on the rim. Although the rim protector 23 is provided in Figure 3, a configuration without the rim protector 23 is also possible, as indicated by the two-dot chain line in Figure 3. Even in this case, a rim line, which is a circular protrusion that protrudes axially outward, is provided on the side of the tire to ensure that the tire 1 is properly mounted on the rim.

[0022] In this example, a plurality of block protrusions 5b, which will be described later, are provided on the tire side surface 13, which is the outer surface in the tire axial direction Z, located inside the ground contact edge T of the tread 10 in the tire radial direction Y and outside the rim line 24 in the tire radial direction Y.

[0023] 1 and 2, a plurality of block protrusions 5b are provided on the tire side surface 13, protruding axially outward from the profile surface 5a of the sidewall 5 and aligned in the tire circumferential direction. The block protrusions 5b improve traction performance and side cut performance during off-road driving.

[0024] The tire 1 is suitable for use as a tire for, for example, a light truck. Note that light trucks include pickup trucks, sports utility vehicles (SUVs), etc. An example of the size of the tire 1 is LT275 / 60R20.

[0025] The tire 1 is formed with a side rib 6 near the tread 10 on the tire side surface 13. The side rib 6 is a convex portion that protrudes axially outward and is formed in a ring shape along the tire circumferential direction. In this embodiment, the portion from the axially outer end of the surface of the shoulder blocks 2 a, 2 b facing radially outward to the side rib 6 is defined as a buttress region, and the portion from the bead 14 to the side rib 6 is defined as a sidewall 5.

[0026] The buttress region may be made of the same rubber as the tread 10, or a different rubber. Meanwhile, the block protrusions 5b on both axial sides of the tire can be blocks of the same shape, but the block protrusions on both axial sides of the tire are not limited to the same shape and may have completely different shapes. The tire 1 may be a tire with no specified mounting direction. Meanwhile, the tire 1 may be configured with a specified mounting direction, and multiple block protrusions 5b may be formed only on the axially outer surface of the portion that faces outboard of the vehicle.

[0027] FIG. 4 is a cross-sectional view taken along line AA in FIG. 2. Hereinafter, the sidewall 5 of the tire 1 will be described in detail with further reference to FIGS. 1 to 4. As shown in FIGS. 1, 2, and 4, the tire 1 has a plurality of block protrusions 5b formed on the sidewall 5. The plurality of block protrusions 5b are arranged at predetermined intervals in the tire circumferential direction. The predetermined intervals may be constant, or may be a variable pitch in which the intervals between the blocks or the circumferential lengths of the blocks are slightly varied in units of a predetermined number. The block protrusions 5b include a first block protrusion 51 and a second block protrusion 52. A step is formed at a boundary 53 between the first block protrusion 51 and the second block protrusion 52, and the first block protrusion 51 is higher than the second block protrusion 52 except for its radially inner end.

[0028] In this embodiment, the block protrusions 5b having substantially the same shape and size are arranged in the tire circumferential direction, but two or more types of blocks having different shapes may be arranged alternately in the tire circumferential direction or in a predetermined pattern. The number of block protrusions 5b arranged in the tire circumferential direction is not particularly limited, but is, for example, 20 to 30.

[0029] The block protrusions 5b can be formed between the side rib 6 and the tire maximum width position P (FIGS. 2 and 3). In this case, good side traction performance and side cut (protection) performance can be ensured. In this specification, the "tire maximum width position P" refers to the position on the profile surface 5a of the sidewall 5 where the axial length of the tire is at its maximum. Furthermore, the "profile surface 5a" of the sidewall 5 refers to the surface of the sidewall 5 facing axially outward when the block protrusions 5b are not formed.

[0030] The block protrusion 5b is an integrated block formed by connecting one first block protrusion 51 and one second block protrusion 52. The first block protrusion 51 and the second block protrusion 52 have substantially the same length in the tire radial direction.

[0031] The tire side surface 13 also has side surfaces 7a, 7b facing axially outward of the multiple shoulder blocks 2a, 2b lined up in the tire circumferential direction. The shoulder blocks 2a, 2b are blocks formed axially outward of the tread 10 and are arranged alternately in the tire circumferential direction. The shoulder blocks 2a, 2b have similar sizes, and each side surface 7a, 7b is located axially inward of the side rib 6 except for the radially inner end of the tire, but the side surface 7b of the shoulder block 2b is recessed axially inward more than the side surface 7a of the shoulder block 2a.

[0032] The shoulder blocks 2a, 2b are separated by grooves 2c, 2d extending in the tire axial direction. The grooves 2c are formed with substantially the same width from between the shoulder blocks 2a, 2b to the side rib 6. On the other hand, the grooves 2d widen near the side rib 6. The side surfaces 7a, 7b of the shoulder blocks 2a, 2b and the grooves 2c, 2d form unevenness in the circumferential direction of the tire in the buttress region of the tire 1. This unevenness improves side traction performance on muddy, sandy, or snowy roads.

[0033] The block protrusions 5b are formed in an area that overlaps with the shoulder blocks 2a, 2b and groove 2c in the tire radial direction, but are not formed in an area that overlaps with the groove 2d in the tire radial direction. That is, the block protrusions 5b are formed at the same circumferential pitch as the pair of shoulder blocks 2a, 2b. The spacing between the block protrusions 5b is wider on the tire maximum width position P side than on the side rib 6 side. In this case, for example, mud removal is improved on muddy ground, improving side traction performance.

[0034] In each block protrusion 5b, the protruding height of the first block protrusion 51 is generally greater than the protruding height of the second block protrusion 52, except for the radially inner end portion. Specifically, the portions between the block protrusions 5b are at the same height as the profile surface 5a of the sidewall 5. As a result, the portions of the sidewall 5 between the side rib 6 and the tire's maximum width position P have unevenness in the tire circumferential direction. This unevenness improves side traction performance on muddy, sandy, or snowy roads. From the perspective of improving side cut performance, it is preferable that the length of the block protrusions 5b along the tire circumferential direction be longer than the distance between the block protrusions 5b.

[0035] The block protrusions 5b and the shoulder blocks 2a, 2b of the tread 10 are preferably arranged in a regular pattern relative to each other. In this case, an integrated regular pattern is formed in the sidewall 5 and the buttress region, which stabilizes side traction performance, for example. In this embodiment, the first block protrusions 51 are formed to be aligned with the shoulder blocks 2a in the tire radial direction, and the second block protrusions 52 are formed to be aligned with the shoulder blocks 2b in the tire radial direction.

[0036] The first block protrusion 51 constituting the block protrusion 5b is sandwiched between two second block protrusions 52, but is continuous with one of the second block protrusions 52 and is not connected to the other second block protrusion 52. The first block protrusion 51 is formed in an area overlapping with the shoulder block 2a in the tire radial direction, and the second block protrusion 52 is formed in an area overlapping with the shoulder block 2b and groove 2c in the tire radial direction. The second block protrusion 52 is larger than the first block protrusion 51 in a side view, and a portion of it extends to a position overlapping with the shoulder block 2a in the tire radial direction.

[0037] As described above, the first block protrusion 51 and the second block protrusion 52 have different protruding heights except for the radially inner end of the tire, with the first block protrusion 51 being taller than the second block protrusion 52. The protruding height of the block protrusion 5b refers to the length along the normal to the profile surface 5a of the sidewall 5 from the profile surface 5a of the sidewall 5 to the side surface 5c of the block protrusion 5b facing axially outward of the tire. The protruding height is sometimes simply referred to as height. The difference in height between the two blocks that make up the block protrusion 5b and the difference in height between the block protrusion 5b and the gap between them creates unevenness in the sidewall 5, which improves side traction performance on muddy, sandy, or snowy roads.

[0038] The first block protrusions 51 have substantially the same height except for, for example, the block ends at the radially inner ends of the tire. On the other hand, the second block protrusions 52 have three regions (a first region 61, a second region 62, and a third region 63) with different heights along the tire radial direction. The height of the second block protrusions 52 is substantially constant in the first region 61 adjacent to the side rib 6 and is lowest at the boundary between the second region 62 and the third region 63. The first block protrusions 51 and the second block protrusions 52 have substantially the same height at the radially inner ends of the tire.

[0039] The first block protrusion 51 has a convex portion 64 located on the inner side in the tire radial direction that is convex in the second direction X2 of the tire circumferential direction. In other words, the first block protrusion 51 has a portion located on the outer side in the tire radial direction (Y1 direction side) closer to the side rib 6 that is concave in the X1 direction. Such unevenness of the first block protrusion 51 contributes to improving side traction performance. The X2-direction end of the convex portion 64 is formed in a substantially straight line in a side view so as to follow the tire radial direction.

[0040] The block ends of the block protrusions 5b may be formed perpendicular to the profile surface 5a, or may be inclined so that the height of the blocks gradually decreases. The radially outer (Y1-direction) end of the convex portion 64 of the first block protrusion 51 has a slope 65 formed thereon that is gentler than the other block ends. By forming the gentle slope 65 at the Y1-direction end of the convex portion 64, air flows more easily along the surface of the sidewall 5, thereby suppressing an increase in air resistance. The inclination angle of the slope 65 with respect to the profile surface 5a is, for example, between 40° and 75°.

[0041] The boundary 53 between the two blocks that make up the block protrusion 5b extends radially from the side rib 6 and bends in the X2 direction at the radial center of the block. Therefore, the tire circumferential length of the portion located on the radially inner side (Y2 direction side) of the first block protrusion 51, excluding the convex portion 64, gradually decreases in the Y2 direction.

[0042] As described above, the height of the second block protrusions 52 varies in the tire radial direction, and in portions other than the Y2 side ends, the first region 61 adjacent to the side rib 6 is the highest. The second region 62 adjacent to the first region 61 in the Y2 direction is inclined so that its height gradually decreases in the Y2 direction, and the third region 63 adjacent to the second region 62 in the Y2 direction is inclined so that its height gradually increases in the Y2 direction. By providing a gentle slope on the surface of the second block protrusions 52, airflow that follows the surface of the second block protrusions 52 is more likely to occur, thereby suppressing an increase in air resistance.

[0043] The second block protrusions 52 are inclined relative to the tire radial direction so that the block ends facing the X2 direction are gradually positioned in the X2 direction as they move in the Y2 direction. The second block protrusions 52 have a tapered shape in which the tire circumferential length at the Y2 direction end is slightly shorter than that at the Y1 direction end.

[0044] In this embodiment, the multiple block protrusions 5b have side surfaces Sa and Sb facing in the tire circumferential direction, a side surface Sc facing in the Y2 direction, a first outer surface S1 and an inclined surface 65 of the first block protrusion 51, and a second outer surface S2 of the second block protrusion 52. The first block protrusion 51 also has a third outer surface S3 continuing from the inner end of the first outer surface S1 in the tire radial direction. The second block protrusion 52 also has a fourth outer surface S4 continuing from the inner end of the second outer surface S2 in the tire radial direction.

[0045] The first, second, third, and fourth outer surfaces S1, S2, S3, and S4 are surfaces facing axially outward of the block protrusion 5b and are top side surfaces. The first outer surface S1 corresponds to the first surface, and the second outer surface S2 corresponds to the second surface. The first outer surface S1 is higher in the protruding direction than the second outer surface S2. On the other hand, the third outer surface S3 and the fourth outer surface S4 have the same height in the protruding direction, are located at the Y2-direction side ends of the block protrusion 5b, and are continuous with each other in the tire circumferential direction.

[0046] In the multiple block protrusions 5b, the surface roughness of the first, second, third, and fourth outer surfaces S1, S2, S3, and S4 is greater than the surface roughness of the portions of the tire side surface 13 other than the multiple block protrusions 5b. For example, the maximum height roughness of the surface roughness of the first, second, third, and fourth outer surfaces S1, S2, S3, and S4 is greater than the surface roughness of the portions of the tire side surface 13 other than the multiple block protrusions 5b, for the same measurement reference length. This makes it possible to suppress the occurrence of shine and blooming on the first, second, third, and fourth outer surfaces S1, S2, S3, and S4 in the tire 1 having the multiple block protrusions 5b on the tire side surface 13, as described below.

[0047] For example, the maximum height roughness of the first outer surface S1 and the second outer surface S2 is in the range of 5 μm to 35 μm when measured in the tire circumferential direction and tire radial direction near the center of gravity of the surface area of ​​each of the first outer surface S1 and the second outer surface S2, when the measurement reference length is 4 mm.

[0048] Note that the side surfaces of the block protrusions 5b other than the first, second, third, and fourth outer surfaces S1, S2, S3, and S4 are difficult to see when viewed from the outside in the tire axial direction, and are lower in height in the protruding direction in the tire axial direction as a whole than the first, second, third, and fourth outer surfaces S1, S2, S3, and S4. Therefore, the surface roughness of the side surfaces of the block protrusions 5b other than the first, second, third, and fourth outer surfaces S1, S2, S3, and S4 is not limited, but may be greater than the surface roughness of the tire side surface 13 other than the block protrusions 5b, similar to the first, second, third, and fourth outer surfaces S1, S2, S3, and S4.

[0049] The first, second, third, and fourth outer surfaces S1, S2, S3, and S4 of the multiple block protrusions 5b are formed by roughened surfaces provided in corresponding portions of the tire mold. The "roughened surfaces" are formed by shot peening. Shot peening will be described in detail later. Meanwhile, portions of the tire side surface 13 other than the block protrusions 5b are subjected to a process that reduces the surface roughness after processing compared to shot peening, such as shot blasting using resin beads, on the surfaces provided in corresponding portions of the tire mold.

[0050] As described above, the first outer surface S1 provided on the first block protrusion 51 is higher in the protruding direction than the second outer surface S2 provided on the second block protrusion 52. That is, the height of the second outer surface S2 is lower than the height of the first outer surface S1. Furthermore, the surface roughness of the first outer surface S1 is greater than the surface roughness of the second outer surface S2.

[0051] For example, if the maximum height roughness of the surface roughness of the first outer surface S1 is RzH and the maximum height roughness of the surface roughness of the second outer surface S2 is RzL, then RzH > RzL. In this case, the measurement reference length for measuring the maximum height roughness of the first outer surface S1 and the maximum height roughness of the second outer surface S2 is the same. For example, the measurement reference length can be 4 mm. This allows the difference in gloss between the first outer surface S1 and the second outer surface S2 to be suppressed even when the block protrusion 51 has the first outer surface S1 and the second outer surface S2 facing axially outward at different heights.

[0052] Meanwhile, the third outer surface S3 of the first block protrusion 51 and the fourth outer surface S4 of the second block protrusion 52 have the same height. The third outer surface S3 and the fourth outer surface S4 have the same surface roughness. Because the third outer surface S3 is lower than the first outer surface S1 and the fourth outer surface S4 is higher than the second outer surface S2, the surface roughness of the third outer surface S3 and the fourth outer surface S4 is intermediate between the roughness of the first outer surface S1 and the second outer surface S2. This minimizes the difference in shine between the outer surfaces S1, S2, S3, and S4.

[0053] Furthermore, when the maximum height roughness of the surface roughness of the first outer surface S1 is RzH and the maximum height roughness of the surface roughness of the second outer surface S2 is RzL, the surface roughness of the first outer surface S1 and the second outer surface S2 is regulated to satisfy 1.2≦RzH / RzL≦2.5. This allows the surface roughness of the first outer surface S1 and the second outer surface S2 to be more appropriately regulated, further reducing the difference in shine between the first outer surface S1 and the second outer surface S2. Furthermore, regulating the surface roughness changes the mirror-like rough surface to an uneven surface, thereby suppressing the occurrence of blooming and further reducing shine.

[0054] Fig. 5 is a schematic diagram showing a tire molding mold 70 as one example of an embodiment. Hereinafter, the tire molding mold 70 will be referred to as mold 70. The mold 70 is a mold for molding the tire 1 shown in Figs. 1 to 4 described above. Using the mold 70, it is possible to mold a tire 1 that has a plurality of block protrusions 5b on the tire side surface 13, and that can suppress the occurrence of shine and blooming on the surfaces of the block protrusions 5b facing axially outward.

[0055] Hereinafter, each member will be described in accordance with the tire axial direction X and tire radial direction Y of the tire 1 molded by the mold 70.

[0056] The mold 70 has a tread mold 71 for molding the surface of the tread of the tire 1b, and a pair of side molds 72 for molding the surfaces of the sidewalls.

[0057] The tread mold 71 has a body 74 having a tread molding surface 73 and a protrusion 75 protruding from the tread molding surface 73 .

[0058] The main body 74 is made of a metal material, for example, an aluminum alloy. As the aluminum alloy, for example, AC4 series, AC7 series, etc. are preferably used. The protrusions 75 are portions that form circumferential grooves in the tire 1. The protrusions 75 are made of the same material as the metal material that makes up the main body 74.

[0059] The side mold 72 has a main body 76 having a side molding surface 77 and a plurality of recesses 78 recessed outward from the side molding surface 77. The main body 76 is made of the same metal material as the main body 74. The plurality of recesses 78 are portions where a plurality of block protrusions 5b are molded on the tire 1.

[0060] The tread mold 71 has a fan shape in a plan view, formed by dividing an annular body into multiple parts in the circumferential direction. The multiple divided tread molds 71 ​​form a continuous annular body with an inner diameter corresponding to the outer diameter of the tire 1 to be molded when in a clamped state, as described below. The upper side mold 72 is annular and fixed to the lower surface of an upper plate (not shown) constituting the vulcanization molding machine, and moves up and down as a first lifting member (not shown) moves up and down. The lower side mold 72 is annular and fixed to the floor surface and to the lower surface of a lower plate (not shown) constituting the vulcanization molding machine. The vulcanization molding machine raises and lowers multiple segments (not shown), one for each tread mold 71, outside the multiple divided tread molds 71, using a first lifting member. Simultaneously with the raising and lowering of the first lifting member, the vulcanization molding machine slides the inclined surfaces of the outer peripheral surfaces of the multiple segments up and down on an inclined cylindrical surface provided at the lower end of a second lifting member (not shown) that moves up and down independently of the first lifting member. As a result, the vulcanization molding machine reciprocates the multiple segments in the radial direction relative to the central axis of the annularly continuous tread mold 71. As a result, the vulcanization molding machine switches the mold 70 between a mold clamped state and a mold open state.

[0061] In the mold 70 configured in this manner, a green tire is placed on the lower tread mold 71 with the tire axial direction aligned vertically when the mold is open. An inflatable bladder is then placed inside the green tire, and air is supplied to the bladder to inflate it. Then, with the inner surface of the green tire held by the outer surface of the bladder, the first lifting member and the second lifting member are raised and lowered to close the mold 70. The rubber of the green tire is pressed against the tread molding surface 73 and the side molding surface 77 by the pressure from the mold 70, and a heat exchange medium adjusted to a predetermined temperature is constantly flowing between the member fixing the upper plate and the member fixing the lower plate. This causes the rubber of the green tire to vulcanize, completing the tire 1 with the predetermined shape.

[0062] In this embodiment, the bottom surfaces of the recesses 78, which are portions of the side molding surface 77 that is the inner surface of the side mold 72 and that form the first, second, third, and fourth outer surfaces S1, S2, S3, and S4, have rough surfaces formed in advance by shot peening. As a result, the bottom surfaces of the recesses 78 have a greater surface roughness than the portions of the side molding surface 77 that form the tire side surface 13 other than the multiple block protrusions 5b. For example, when shot peening is performed on the side mold 72, the portions of the inner surface of the side mold 72 that are not to be shot peened are masked. Furthermore, the portions of the inner surface of the side mold 72 that form the portions other than the multiple block protrusions 5b are subjected to a process that results in a lower surface roughness after processing than shot peening, such as shot blasting using resin beads.

[0063] Furthermore, of the first, second, third, and fourth outer surfaces S1, S2, S3, and S4, the first outer surface S1 is the roughest, the second outer surface S2 is the smoothest, and the third outer surface S3 and the fourth outer surface S4 have intermediate roughnesses. Therefore, when shot peening is performed on each of the outer surfaces S1, S2, S3, and S4, the inner surface of the side mold 72 is masked in order so that only the first outer surface S1, only the second outer surface S2, or only the third outer surface S3 and the fourth outer surface S4 are exposed, respectively.

[0064] Furthermore, when shot peening is performed, as described above, if the maximum height roughness of the surface roughness of the first outer surface S1 is RzH and the maximum height roughness of the surface roughness of the second outer surface S2 is RzL, the surface roughnesses of the first outer surface S1 and the second outer surface S2 are regulated to satisfy 1.2≦RzH / RzL≦2.5.

[0065] FIG. 6 shows the preferred conditions for performing shot peening. Shot peening processes the inner surface of the side mold 72 by ejecting spherical metallic shot material from a nozzle onto the inner surface of the side mold 72. The side mold 72 is formed in advance into a rough shape by casting or the like. As shown in FIG. 6, the shot material can be made of one of zircon, iron, cast steel, and ceramics. The sphericity of the shot material can be 5 μm or less, and the average particle size can be 50 μm or more and 400 μm or less. The specific gravity of the shot material is 1.2 kg / m 3 More than 15kg / m 3 It can be as follows:

[0066] The Mohs hardness of the blast material is 5.0 or more and 9.0 or less, the Mohs hardness of the side mold 72 is 2.0 or more and 5.0 or less, and the difference in Mohs hardness between the blast material and the side mold 72 can be 3.0 or more and 5.0 or less.

[0067] Furthermore, the projection pressure when projecting the projection material from the nozzle can be 100 kPa or more and 1000 kPa or less, and the projection time can be 30 seconds or more and 10 minutes or less per side mold 72. In addition, the projection speed of the projection material can be 0.5 m / s or more and 7 m / s or less, and the distance from the nozzle to the projection position on the inner surface of the side mold 72 can be 50 mm or more and 200 mm or less.

[0068] According to the tire 1 and mold 70 described above, in a configuration in which the tire side surface 13 of the obtained tire 1 has a plurality of block protrusions 5b, it is possible to suppress the shine on the surface of the block protrusions 5b facing outward in the tire axial direction, and also to prevent the surface from becoming a mirror finish, thereby suppressing the occurrence of the bloom phenomenon.

[0069] 7A and 7B, we will explain why this embodiment can suppress glare caused by sunlight reflection on the surface of the block protrusion 5b facing axially outward. First, we will explain the disadvantages of a comparative example using FIG. 7A. Unlike this embodiment, the comparative example has a smooth surface with the same surface roughness as the tire side surface other than the block protrusion 5b1. In this comparative example, when the position of light at the base end of arrows A1 and A2 is misaligned with the human viewpoint E in the surface direction of the tire sidewall, as shown by arrows A1 and A2, light reflected by the surface of the block protrusion 5b1 facing axially outward is likely to be directed toward the human viewpoint E. Therefore, the surface of the block protrusion 5b1 facing axially outward is likely to become shiny.

[0070] 7B , in this embodiment, the axially outward facing surface of the block protrusions 5b is rougher than the rest of the tire sidewall. In this embodiment, if the position of the light at the base ends of arrows B1 and B2 is misaligned with the human viewpoint E in the direction of the tire sidewall, the light reflected by the axially outward facing surface of the block protrusions 5b is likely to deviate from the vicinity of the human viewpoint E, as shown by arrows B1 and B2. This reduces the shine on the axially outward facing surface of the block protrusions 5b.

[0071] In the above embodiment, the axially outward facing surface of the block protrusion 5b has the first, second, third, and fourth outer surfaces S1, S2, S3, and S4, but the present invention is not limited to this. For example, the axially outward facing surface of the block protrusion may have only a first outer surface and a second outer surface of different heights, or only an outer surface of a fixed height, or a plurality of four or more surfaces of different heights. [Explanation of symbols]

[0072] 1 pneumatic tire (tire), 2a, 2b shoulder blocks, 2c, 2d grooves, 5 sidewall, 5a profile surface, 5b, 5b1 block protrusions, 6 side ribs, 7a, 7b side surfaces, 10 tread, 12 sidewall, 13 tire side surface, 14 bead, 18 rim strip, 19 carcass, 20 belt layer, 21 narrow belt, 22 wide belt, 23 rim protector, 24 rim line, 51 first block protrusions, 52 second block protrusions, 53 boundary, 61 first region, 62 second region, 63 third region, 64 convex portion, 65 inclined surface, P tire maximum width position, T ground contact edge.

Claims

1. The tire side surface is an axially outer surface of the tire that is radially inward of the ground contact edge of the tread and radially outward of the rim line. The tire side surface has a plurality of block protrusions that protrude axially outward from a plurality of positions in the tire circumferential direction, A pneumatic tire, wherein the surfaces of the plurality of block protrusions facing outward in the tire axial direction have a surface roughness greater than that of the tire side surface other than the plurality of block protrusions.

2. surfaces of the plurality of block protrusions facing outward in the tire axial direction are formed by rough surfaces provided in corresponding portions of a tire molding die, The roughened surface is formed by shot peening. The pneumatic tire according to claim 1 .

3. The surfaces of the plurality of block protrusions facing outward in the tire axial direction have a first surface and a second surface that is lower in height in the protruding direction than the first surface, and the surface roughness of the first surface is higher than the surface roughness of the second surface. The pneumatic tire according to claim 1 .

4. When the maximum height roughness of the surface roughness of the first surface is RzH and the maximum height roughness of the surface roughness of the second surface is RzL, The surface roughness of the first surface and the second surface is regulated to satisfy 1.2≦RzH / RzL≦2.

5. The pneumatic tire according to claim 3.

5. A mold for molding a pneumatic tire includes a tire side surface, which is an axially outer surface of the tire, located radially inward of a ground contact edge of a tread and radially outward of a rim line, and includes a plurality of block protrusions protruding axially outward from a plurality of positions in the tire circumferential direction, A mold for molding a pneumatic tire, in which a portion forming a surface of the plurality of block protrusions facing outward in the tire axial direction has a surface roughness greater than a portion of the tire side surface forming other than the plurality of block protrusions.

6. a portion of each of the plurality of block protrusions forming a surface facing outward in the height direction has a rough surface formed by shot peening; The mold for molding a pneumatic tire according to claim 5.

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