pneumatic tires

Abstract

To suppress increase in air resistance during travelling, near the center in the vertical direction of a tire and near a contacted road surface in the pneumatic tire having a plurality of protrusions on a tire side surface.SOLUTION: A tire 1 being one example of an embodiment includes: a plurality of outside protrusions 31 provided aligning in the tire circumferential direction in a tire side surface 13 being a tire axial outside surface on the tire radially inside from a contacted ground end T of a tread 10 and on the tire radially outside from a rim line, protruding toward the outside from a tire surface, and having different protrusion amounts of at least some of the adjacent outside protrusions; and a plurality of inside protrusions 41 provided aligning in the tire radial direction in the tire radially inside from the plurality of outside protrusions 31 on the tire side surface, protruding toward the outside from the tire surface, and having different protrusion amounts of at least some of the adjacent inside protrusions.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire provided with protrusions provided on a tire side surface which is an outer surface in the tire axial direction on the inner side in the tire radial direction from the ground contact end of the tread.

Background Art

[0002] In recent years, the spread of electric vehicles and hybrid vehicles has been rapidly progressing, and a strong reduction in the resistance against the driving force has been demanded. As this resistance, there is air resistance during vehicle running. In order to reduce the air resistance on the tire side surface, it is conceivable to eliminate the protrusions protruding from the tire side surface as much as possible, but there is room for improvement from the aspect of improving the design of the tire.

[0003] Patent Document 1 describes providing a plurality of columnar protrusions protruding from the surface of the sidewall portion of a tire to generate turbulent flow. In Patent Document 1, it is said that turbulent flow can be generated by the edge of the connecting portion between the tip surface and the sidewall surface of the protrusion.

[0004] Patent Document 2 describes that a plurality of protrusions protruding outward from the tire are regularly arranged on the surface of the tire side portion, the maximum width and the maximum height of the protrusions are within a predetermined range, and the arrangement interval of the protrusions along the tire surface is greater than 0.1 μm and less than 100 μm. In Patent Document 2, it is said that an optimal air relaxation layer can be formed on the tire surface by this.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] To achieve both improved tire aesthetics and reduced air resistance during vehicle operation, it is conceivable to provide multiple protrusions on the tire side surface, as described in Patent Document 1. However, a tire with multiple protrusions of a constant height on its side surface still has room for improvement in terms of reducing the increase in air resistance near the center of the tire in the vertical direction during operation, and in reducing the increase in air resistance near the road contact point.

[0007] The object of the present invention is to provide a pneumatic tire that has a configuration with multiple protrusions on the tire side surface and can suppress the increase in air resistance during driving near the center of the tire in the vertical direction and near the road contact point. [Means for solving the problem]

[0008] The pneumatic tire according to the present invention comprises a plurality of outer protrusions arranged in the circumferential direction of the tire and projecting outward from the tire surface on the tire side surface, which is the outer surface in the axial direction of the tire, located radially inward from the contact edge of the tread and radially outward from the rim line, wherein at least some of the protrusion amounts of adjacent outer protrusions are different; and a plurality of inner protrusions arranged radially inward from the plurality of outer protrusions on the tire side surface and projecting outward from the tire surface, wherein at least some of the protrusion amounts of adjacent inner protrusions are different. [Effects of the Invention]

[0009] According to the pneumatic tire of the present invention, in a configuration in which the tire side surface has multiple protrusions, the pressure resistance caused by the formation of the outer protrusions can be reduced near the road contact point where the multiple outer protrusions are aligned in the direction of vehicle travel. This helps to suppress the increase in air resistance during driving near the road contact point of the tire. Furthermore, the pressure resistance caused by the formation of the inner protrusions can be reduced near the vertical center of the tire where the multiple inner protrusions are aligned in the direction of vehicle travel. This helps to suppress the increase in air resistance during driving near the vertical center of the tire. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view showing a portion of the circumferential direction of a pneumatic tire, which is an example of an embodiment. [Figure 2] Figure 1 shows the upper part of the tire side surface as viewed in the direction of the tire axis. [Figure 3] This figure shows a meridional cross-section of the pneumatic tire of the embodiment, with the side blocks omitted. [Figure 4] In this embodiment, the diagram shows a plurality of outer protrusions located at both the upper and lower ends of the tire, viewed from one side in the vertical direction. [Figure 5] This is a view of the outer projection from the outside in the height direction. [Figure 6] In this embodiment, the diagram shows a plurality of inner protrusions located at both the upper and lower ends of the tire, viewed from one side in the vehicle's front-rear direction. [Figure 7] Figure 1 is a schematic diagram showing the airflow near the road contact point on the axial outer surface of a pneumatic tire during vehicle travel. [Figure 8] This figure corresponds to Figure 4, showing the airflow near the multiple outer protrusions at the lower end of the pneumatic tire according to the embodiment. [Figure 9] This figure shows the external shape of a protrusion used in a pneumatic tire, as in another embodiment. [Figure 10] This figure corresponds to Figure 4, showing an alternative embodiment of a pneumatic tire. [Figure 11] This figure corresponds to Figure 6, showing an alternative embodiment of a pneumatic tire. [Figure 12] This figure corresponds to Figure 4, showing the airflow near the multiple outer protrusions at the lower end of the pneumatic tire according to the embodiment. [Modes for carrying out the invention]

[0011] Hereinafter, an example of an embodiment of a pneumatic tire according to the present invention will be described in detail while referring to the drawings. The embodiment described below is merely an example, and the present invention is not limited to the following embodiments. Also, selectively combining the components of the plurality of embodiments and modification examples described below is included in the present invention.

[0012] FIG. 1 is a perspective view showing a partial circumferential direction of a pneumatic tire 1 which is an example of an embodiment. FIG. 2 is a view looking at the upper part of the tire side surface 13 of FIG. 1 in the tire axial direction. FIG. 3 is a view in which side blocks are omitted in the meridian cross section of the pneumatic tire 1 of the embodiment. Hereinafter, the "pneumatic tire 1" will be referred to as the "tire 1".

[0013] The tire 1 includes a tread 10 which is a portion that contacts the road surface. The tread 10 has a tread pattern including a plurality of blocks such as shoulder blocks 2a, 2b, etc., and is formed in an annular shape along the tire circumferential direction. A plurality of grooves 2c, 2d that partition the blocks are formed in the tread 10. The tread 10 has a ground contact end T. In FIG. 2, the first direction in the tire circumferential direction is indicated by X1, the second direction in the tire circumferential direction is indicated by X2, the outer side in the tire radial direction is indicated by Y1, and the inner side in the tire radial direction is indicated by Y2.

[0014] Hereinafter, as the configuration of the tire 1, the portion on the outer side (OUT side) of the vehicle centered around the center in the tire axial direction will be described. The tire 1 is symmetric between the portion on the outer side of the vehicle and the portion on the inner side of the vehicle with respect to the shape other than the protrusions of the tire side surface 13 described later.

[0015] The tire 1 includes a sidewall 5 provided at an end portion outside the tire axial direction from the tread 10 and bulging most outside in the tire axial direction, and a bead 14 (FIG. 3) fixed to the rim of the wheel. The sidewall 5 and the bead 14 are formed in an annular shape along the tire circumferential direction. The sidewall 5 extends radially inward from both axial ends of the tread 10 in the tire axial direction. As shown in FIG. 3, at the radially inner end of the tire 1 in the Y direction, a rim strip 18 forming the outer surface of the bead 14 is provided adjacent to the sidewall 5.

[0016] The tire 1 is a pneumatic tire filled with air at a predetermined pressure. The tread 10 is composed of tread rubber. The sidewall 5 is composed of a different type of sidewall rubber from the tread rubber.

[0017] In this specification, unless otherwise specified, the dimensions of each part of the tire are the dimensions measured in the non-loaded normal state where an unused tire is mounted on a regular rim and filled with air to a regular internal pressure.

[0018] The "grounding end T" means both axial ends in the X direction of the region that contacts the flat road surface when a load of 88% of the regular load at the regular internal pressure is applied in a state where an unused tire 1 is mounted on a regular rim and filled with air to a regular internal pressure.

[0019] Here, "standard rim" refers to the rim defined by the tire standard, which is "standard rim" for JATMA, "Design Rim" for TRA, and "Measuring Rim" for ETRTO. "Standard internal pressure" is "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. "Standard load" is "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO.

[0020] As shown in Figure 3, the tire 1 comprises a carcass 19 and a belt layer 20. The carcass 19 is a cord layer covered with rubber, forming the skeleton of the tire 1 that can withstand loads, impacts, air pressure, etc. The belt layer 20 is a reinforcing band placed between the tread rubber and the carcass 19. The belt layer 20 tightens the carcass 19 and increases the rigidity of the tire 1. The belt layer 20 is formed by overlapping multiple belts in the tire radial direction Y: a narrow belt 21 and a wide belt 22, which is provided radially outward from the narrow belt 21 and has a greater length in the tire axial direction Z than the narrow belt 21. Each belt 21, 22 is formed by covering multiple cords with rubber, which are arranged in a direction inclined with respect to the tire circumferential direction. In adjacent belts 21, 22, the cords are inclined in opposite directions with respect to the tire circumferential direction so that their cords intersect. The cords are made of steel or the like.

[0021] Between the belt layer 20 and the tread rubber, a belt reinforcement layer (not shown) is provided, which extends in the circumferential direction of the tire and covers the entire belt layer 20 in the axial direction Z of the tire. The belt reinforcement layer is formed by covering cords that extend substantially in the circumferential direction of the tire with rubber. The cords are made of organic fibers or the like.

[0022] Furthermore, a rim protector 23 is provided as part of the rim strip rubber that forms the rim strip 18, projecting outward in the tire axial direction. The rim line 24 is provided in an annular shape along the tire circumferential direction at the apex located at the outer end of the rim protector 23 in the tire axial direction. The rim protector 23 has the function of protecting the rim from damage. The rim line 24 is a line used to confirm that the tire 1 is mounted on the rim in the correct position by checking the gap between the tire and the rim. In Figure 3, a rim protector 23 is provided, but as shown by the dashed line in Figure 3, a configuration without a rim protector 23 is also possible. Even in this case, a rim line, which is an annular projection projecting outward in the tire axial direction, is provided on the side of the tire to confirm that the tire 1 is mounted on the rim in the correct position.

[0023] In this example, a plurality of outer protrusions 31 (Figure 1) and a plurality of inner protrusions 41 (Figure 1), described later, are provided on the tire side surface 13, which is the outer surface in the tire axial direction Z, located radially Y inward from the contact edge T of the tread 10 and radially Y outward from the rim line 24.

[0024] As shown in Figures 1 and 2, the tire side surface 13 is provided with a plurality of side blocks 5b that protrude outward in the tire axial direction from the profile surface 5a of the sidewall 5 and are arranged in the tire circumferential direction. The side blocks 5b improve traction performance and side cut performance during off-road driving. In addition, a plurality of inner protrusions 41, which will be described later, are formed on the outer surface of the side block 5b in the tire axial direction and are arranged in the tire radial direction to reduce air resistance.

[0025] Tire 1 is suitable, for example, for light trucks. Light trucks include pickup trucks, sport utility vehicles (SUVs), etc. An example of a tire size for Tire 1 is LT275 / 60R20.

[0026] The tire 1 has a side rib 6 formed near the tread 10 on the tire side surface 13. The side rib 6 is a convex portion that protrudes outward in the tire axial direction and is formed in an annular shape along the tire circumferential direction. In this embodiment, the portion from the outer end of the surface of the shoulder blocks 2a, 2b facing outward in the tire radial direction to the side rib 6 is defined as the buttress region, and the portion from the bead 14 to the side rib 6 is defined as the sidewall 5. The shape of the outer side surfaces 7a, 7b of the shoulder blocks 2a, 2b facing outward in the tire axial direction affects the shape of the buttress region.

[0027] The buttress area may be made of the same rubber as the tread 10, or it may be made of a different rubber. On the other hand, the side blocks 5b on both sides of the tire axial direction may be blocks of the same shape, but the side blocks on both sides of the tire axial direction are not limited to the same shape and may be completely different shapes. The tire 1 may be a tire without a specified mounting direction. On the other hand, the tire 1 may be configured with a specified mounting direction, and a plurality of outer protrusions 31 and a plurality of inner protrusions 41, described later, may be formed only on the axial outer surface of the portion that faces the outside of the vehicle.

[0028] The sidewall 5 and buttress region of tire 1 will be described in detail below with further reference to Figures 1 and 2. As shown in Figures 1 and 2, tire 1 has a plurality of side blocks 5b formed on the sidewall 5. The plurality of side blocks 5b are arranged at predetermined intervals in the circumferential direction of the tire. The predetermined interval may be constant, or it may be a variable pitch in which the spacing between blocks or the circumferential length of the blocks is slightly changed in units of a predetermined number. The side blocks 5b also include a first side block 51 and a second side block 52. A step is formed at the boundary 53 between the first side block 51 and the second side block 52, and the first side block 51 protrudes outward in the tire axial direction compared to the second side block 52.

[0029] In this embodiment, side blocks 5b having substantially the same shape and size are arranged in the circumferential direction of the tire. However, two or more types of blocks with different shapes may be arranged alternately in the circumferential direction of the tire, or in a predetermined pattern. The number of side blocks 5b arranged in the circumferential direction of the tire is not particularly limited, but one example is 20 to 30.

[0030] The side block 5b can be formed between the side rib 6 and the tire's maximum width position P. In this case, it becomes easier to reduce air resistance while ensuring good side traction and side cut (protection) performance. In this specification, "tire's maximum width position P" means the position on the profile surface 5a of the sidewall 5 where the tire axial length is maximum. Also, "profile surface 5a" of the sidewall 5 means the surface of the sidewall 5 facing outward in the tire axial direction when the side block 5b is not formed.

[0031] The side block 5b is a block formed by connecting one first side block 51 and one second side block 52. The lengths of the first side block 51 and the second side block 52 along the tire radial direction are substantially the same.

[0032] The tire side surface 13 is also provided with multiple shoulder blocks 2a and 2b, each with side surfaces 7a and 7b facing outward in the tire axial direction, arranged in the circumferential direction of the tire. The shoulder blocks 2a and 2b are blocks formed on the axially oriented side of the tread 10 and are arranged alternately in the circumferential direction of the tire. The shoulder blocks 2a and 2b are of similar size to each other, and their respective side surfaces 7a and 7b are located axially inward of the side rib 6, except for the inner end in the radial direction of the tire. However, the side surface 7b of shoulder block 2b is more deeply recessed axially inward than the side surface 7a of shoulder block 2a.

[0033] The shoulder blocks 2a and 2b are separated by grooves 2c and 2d that extend in the axial direction of the tire. Grooves 2c are formed with substantially the same width from between each block to the side rib 6. On the other hand, groove 2d widens near the side rib 6. The sides 7a and 7b of the shoulder blocks 2a and 2b and grooves 2c and 2d create irregularities in the buttress region of the tire 1 in the circumferential direction. These irregularities improve side traction performance on muddy, sandy, or snowy roads.

[0034] The side blocks 5b are formed in the area that overlaps with the shoulder blocks 2a, 2b and groove 2c in the tire radial direction, but not in the area that overlaps with groove 2d in the tire radial direction. In other words, the side blocks 5b are formed in the tire circumferential direction at the same pitch as the shoulder block pair 2a, 2b. The spacing between the side blocks 5b is wider on the tire's maximum width position P side than on the side rib 6 side. In this case, for example, mud shedding performance is improved in muddy terrain, and side traction performance is enhanced.

[0035] Multiple outer protrusions 31 are arranged in a line in the tire circumferential direction on the sides 7a and 7b of each shoulder block 2a and 2b that face outward in the tire axial direction. Each of the multiple outer protrusions 31 protrudes outward from the tire surface, and the amount of protrusion of the multiple outer protrusions 31 changes in a mountain shape from the first end (e.g., the X1 side end in Figure 2) to the second end (e.g., the X2 side end in Figure 2) in the tire circumferential direction. As a result, at least some of the adjacent outer protrusions 31 have different amounts of protrusion. The multiple outer protrusions 31 provided on each shoulder block 2a and 2b form an outer protrusion group 30. Therefore, the multiple outer protrusion groups 30 are provided at intervals in the tire circumferential direction depending on the position of each shoulder block 2a and 2b. The spacing of the outer protrusion groups 30 is greater than the spacing of the outer protrusions 31 that form each outer protrusion group 30. The arrangement positions of the multiple outer protrusions 31 and the configuration of each outer protrusion 31 will be described in detail later.

[0036] On the side surface 5c of each side block 5b, which is the top surface of the first side block 51 and faces outward in the tire axial direction, a plurality of inner protrusions 41 are arranged in a line in the tire radial direction. Each of the plurality of inner protrusions 41 protrudes outward from the tire surface, and the amount of protrusion of the plurality of inner protrusions 41 changes in a mountain shape from the first end (e.g., outer end) to the second end (e.g., inner end) in the tire radial direction. As a result, the plurality of inner protrusions 41 are arranged in a line in the tire radial direction, inside the plurality of outer protrusions 31 on the tire side surface 13.

[0037] Furthermore, of the multiple inner protrusions 41, at least some adjacent inner protrusions 41 have different protrusion amounts. The multiple inner protrusions 41 provided on each side block 5b form an inner protrusion group 40. For this reason, the multiple inner protrusion groups 40 are spaced apart in the tire circumferential direction according to the position of each side block 5b. These multiple outer protrusions 31 and multiple inner protrusions 41 create airflow along the surface of the sidewall 5, effectively reducing air resistance during driving.

[0038] Multiple outer protrusions 31 may be arranged in a line in the tire radial direction on the side surface of the second side block 52 facing outward in the tire axial direction. However, as in this example, by providing the inner protrusions 41 on the first side block 51, which has a greater overall protrusion height than the second side block 52, air resistance during driving can be reduced more significantly. Next, the shape of each side block 5b will be described in detail with reference to Figures 1 and 2.

[0039] The portion located between the side blocks 5b is at the same height as the profile surface 5a of the sidewall 5. As a result, irregularities are formed in the circumferential direction of the tire in the portion located between the side rib 6 of the sidewall 5 and the tire's maximum width position P. These irregularities improve side traction performance on muddy, sandy, or snowy roads. From the viewpoint of improving side cut performance, it is preferable that the length of the side blocks 5b along the circumferential direction of the tire is longer than the distance between the side blocks 5b.

[0040] It is preferable that the side block 5b and the shoulder blocks 2a and 2b of the tread 10 are arranged in a regular pattern that is related to each other. In this case, an integrated and regular pattern is formed on the sidewall 5 and the buttress region, which stabilizes side traction performance and improves the effect of reducing air resistance. In this embodiment, the first side block 51 is formed to be aligned with the shoulder block 2a in the tire radial direction, and the second side block 52 is formed to be aligned with the shoulder block 2b in the tire radial direction.

[0041] The first side block 51, which constitutes the side block 5b, is sandwiched between two second side blocks 52, but is continuous with one of the second side blocks 52 and not connected to the other. The first side block 51 is formed in a region that overlaps with the shoulder block 2a in the tire radial direction, and the second side block 52 is formed in a region that overlaps with the shoulder block 2b and the groove 2c in the tire radial direction. The second side block 52 is larger than the first side block 51, and a portion of it extends to a position that overlaps with the shoulder block 2a in the tire radial direction.

[0042] As described above, the first side block 51 and the second side block 52 have different heights, with the first side block 51 being higher. The height of the side block 5b refers to the length along the normal direction of the profile surface 5a from the profile surface 5a of the sidewall 5 to the side surface 5c of the side block 5b. The difference in height between the two blocks that make up the side block 5b, and the difference in height between the side block 5b and the gap between them, creates irregularities on the sidewall 5, which improve side traction performance on muddy, sandy, or snowy roads.

[0043] The first side block 51 has substantially the same height, except for, for example, the block ends on both sides in the radial direction of the tire. On the other hand, the second side block 52 has three regions (first region 61, second region 62, and third region 63) with different heights along the radial direction of the tire. The height of the second side block 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 side block 51 and the second side block 52 are substantially the same height at the inner end in the radial direction of the tire.

[0044] The first side block 51 has a convex portion 64 located on the inner side in the tire radial direction, which is convex in the second direction X2 in the tire circumferential direction. In other words, the first side block 51 has a shape that is recessed in the X1 direction in the portion located on the outer side (Y1 direction side) in the tire radial direction, which is close to the side rib 6. Such irregularities in the first side block 51 contribute to improving side traction performance. The X2 direction end of the convex portion 64 is formed to be approximately straight in a side view, along the tire radial direction.

[0045] The block ends of the side block 5b may be formed perpendicular to the profile surface 5a, or they may be inclined so that the height of the block gradually decreases. The outer (Y1 direction) end of the convex portion 64 of the first side block 51 has a slope 65 that is gentler than the other block ends. By forming a gentle slope 65 at the Y1 direction end of the convex portion 64, airflow along the surface of the sidewall 5 is more easily generated, and the increase in air resistance can be suppressed. The inclination angle of the slope 65 with respect to the profile surface 5a is, for example, 40° or more and 75° or less.

[0046] The boundary 53 between the two blocks that make up the side block 5b extends from the side rib 6 along the tire radial direction and bends in the X2 direction at the center of the block in the tire radial direction. As a result, the portion of the first side block 51 located on the inner side (Y2 direction side) in the tire radial direction, except for the convex portion 64, gradually decreases in length in the tire circumferential direction toward the Y2 direction.

[0047] As described above, the height of the second side block 52 changes in the radial direction of the tire, and in parts other than the side end in the Y2 direction, 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 sloped so that its height gradually decreases toward the Y2 direction, and the third region 63 adjacent to the second region 62 in the Y2 direction is sloped so that its height gradually increases toward the Y2 direction. By providing a gentle slope on the surface of the second side block 52, airflow along the surface of the second side block 52 is more easily generated, and the increase in air resistance can be suppressed.

[0048] The second side block 52 is inclined with respect to the tire radial direction such that the block end facing the X2 direction gradually moves toward the Y2 direction. The second side block 52 has a tapered shape in which the tire circumferential length is slightly shorter at the Y2 direction end than at the Y1 direction end.

[0049] Next, with reference to Figures 1 to 6, we will explain in detail the multiple outer protrusions 31 provided on the sides 7a and 7b of the shoulder blocks 2a and 2b, and the multiple inner protrusions 41 provided on the side 5c of the side block 5b.

[0050] Figure 4 is a view of the multiple outer protrusions 31 located at each of the upper and lower ends of the tire 1, as seen from one side in the vertical direction, in an embodiment. Figure 5 is a view of the outer protrusions 31 as seen from the outside in the height direction. Figure 6 is a view of the multiple inner protrusions 41 located at each of the upper and lower ends of the tire 1, as seen from one side in the vehicle's longitudinal direction, in an embodiment.

[0051] As shown in Figures 1, 2, and 4, a group of outer protrusions 30, consisting of multiple outer protrusions 31, is provided at multiple positions in the tire circumferential direction on the sides 7a and 7b of the shoulder blocks 2a and 2b. The multiple outer protrusions 31 are columnar in shape, such as cylindrical shapes, that project outward from the sides 7a and 7b of the shoulder blocks 2a and 2b in a direction substantially coinciding with the tire axial direction, and approximately normal to the sides 7a and 7b.

[0052] As shown in Figure 5, the shape of the base end of the outer projection 31, when viewed from the outside in the height direction, is circular. The shape and size of the base ends of multiple outer projections 31 are substantially the same. Here, "circular" means that the ratio of the lengths in the vertical and horizontal directions, which are mutually orthogonal directions, is between 0.85 and 1.15. In Figure 5, the vertical direction is the direction of arrow A, and the horizontal direction is the direction of arrow B. That is, when the vertical length is LA and the horizontal length is LB, a shape that satisfies 0.85 ≤ LA / LB ≤ 1.15 is defined as "circular". As a result, air can flow smoothly around the outer projection 31 along the curved shape of the outer edge, as shown by arrows A1 and A2 in Figure 5, thus achieving an effect of suppressing the increase in air resistance. Note that the outer surface of the outer projection 31 may be a tapered surface that narrows towards the tip.

[0053] The multiple outer protrusions 31 shown in Figure 4 are arranged in the circumferential direction of the tire, as shown in Figure 2. Furthermore, the amount of protrusion of the multiple outer protrusions 31 forming the group of outer protrusions 30 changes in a V-shape from the first end (e.g., the left end in Figure 4) to the second end (e.g., the right end in Figure 4) in the circumferential direction of the tire. Here, "amount of protrusion" is the length of the protrusion direction of each outer protrusion 31 in the direction normal to the tire surface. The definition of the amount of protrusion is the same for the inner protrusions 41, which will be described later. This makes it possible to suppress the increase in air resistance during driving near the contact point of the tire with the road surface, as will be described later.

[0054] In Figure 4, the outer protrusion group 30 is formed by seven outer protrusions 31, but the number of outer protrusions 31 forming the outer protrusion group 30 can be three or more. Furthermore, the height of the multiple outer protrusions 31 only needs to change in a mountain shape overall, and some adjacent outer protrusions 31 may have the same height. On the other hand, in order to smooth the airflow, the number of outer protrusions 31 is preferably five or more, and more preferably seven or more. Moreover, for the multiple outer protrusions 31 of the outer protrusion group 30, it is preferable that the height of the intermediate outer protrusion 31 having the maximum height is twice or less the height of the outer protrusions 31 at both ends having the minimum height. This configuration prevents excessive changes in the height of the multiple outer protrusions 31, thereby achieving a further suppression of increased air resistance.

[0055] As shown in Figures 1, 2, and 6, on the side surface 5c of the side block 5b, a group of inner protrusions 50 consisting of multiple inner protrusions 41 is provided at multiple positions in the tire circumferential direction, inward from the multiple outer protrusions 31 in the tire radial direction. Each group of inner protrusions 40 has multiple inner protrusions 41 arranged in a line in the tire radial direction. The multiple inner protrusions 41 are columnar in shape, such as a cylindrical shape, that project outward from the side surface 5c of the side block 5b in a direction substantially coinciding with the tire axial direction, and approximately normal to the side surface 5c of the side block 5b. Furthermore, the shape of the base end of the inner protrusion 41 when viewed from the outside in the height direction is circular, similar to the outer protrusions 31. The shape and size of the base ends of the multiple inner protrusions 41 are substantially the same. This allows air to flow smoothly around the inner protrusions 41 along the curved shape of the outer edge, thereby suppressing the increase in air resistance. The outer surface of the inner protrusion 41 may be a tapered surface that narrows towards the tip.

[0056] The multiple inner protrusions 41 shown in Figure 6 are arranged in the radial direction of the tire, as shown in Figure 2. Furthermore, the amount of protrusion of the multiple inner protrusions 41 forming the inner protrusion group 40 changes in a V-shape from the first end (e.g., the upper end in Figure 6) to the second end (e.g., the lower end in Figure 6) in the radial direction of the tire. This makes it possible to suppress the increase in air resistance during driving near the vertical center of the tire 1, as will be described later.

[0057] The number of inner protrusions 41 forming the inner protrusion group 40 may be three or more, but five or more are preferable, and seven or more are preferable, in order to smooth the airflow. Furthermore, the height of the multiple inner protrusions 41 should change in a mountain shape overall, and some adjacent inner protrusions 41 may have the same height. In addition, for the multiple inner protrusions 41 of the inner protrusion group 40, it is preferable that the height of the middle inner protrusion 41 having the maximum height is twice or less the height of the inner protrusions 41 at both ends having the minimum height. This configuration prevents excessive changes in the height of the multiple inner protrusions 41, thereby providing a further effect of suppressing the increase in air resistance.

[0058] Referring to Figure 3, the preferred range for forming the outer protrusions 31 and inner protrusions 41 will be described. The multiple outer protrusions 31 are preferably formed on the outer surface of the tire within a radial length range R1, corresponding to 5% to 15% of the tire cross-sectional height H, centered at position Q, which coincides with the outer end of the wide belt 22 in the tire axial direction and the tire radial direction. In Figure 3, the arrow R1 indicates the tire radial length range R1. Therefore, position Q is located at the center of the tire radial length range R1 on the outer surface of the tire. In this case, the effect of providing multiple outer protrusions 31 becomes more pronounced.

[0059] It is preferable that the multiple inner protrusions 41 are formed on the outer surface of the tire within a radial length range R2 that corresponds to 10% to 35% of the tire cross-sectional height H, centered on the tire maximum width position P, which is the tire radial position where the maximum tire width is defined. In Figure 3, the tire radial length range R2 is indicated by the arrow R2. Therefore, the tire maximum width position P is located at the center of the tire radial length range R2 on the outer surface of the tire. In this case, the effect of providing multiple inner protrusions 41 becomes more pronounced.

[0060] To form each of the multiple outer protrusions 31 and the multiple inner protrusions 41, convex portions are formed on the tire surface during tire manufacturing. For example, to form convex portions on the tire, the mold is processed using machining, EDM (electrical discharge machining), or laser processing to provide concave portions in the mold. Alternatively, as described in Japanese Patent Application Publication No. 2017-100406, a vent plug may be embedded in the mold. In this case, the mold includes a molding surface that contacts the outer surface of the tire set in the cavity, and a vent plug fitted into an exhaust hole that opens on the molding surface. The vent plug has a cylindrical housing with an exhaust passage inside, a stem inserted into the housing and serving as a valve body for opening and closing the exhaust passage, and a biasing member that biases the stem toward the cavity to open the exhaust passage. The stem has a head at the tip of a columnar body, which is larger in diameter than the body and closes the exhaust passage by contacting the inner surface of the opening in the housing. The top surface of the housing opening on the cavity side, and the top surface of the stem head when the exhaust passage is closed, are both positioned on the side opposite the cavity from the molded surface. As a result, unvulcanized rubber flows into the area inside the exhaust hole where the inner end is blocked by the top surface of the housing opening and the top surface of the stem head, forming a protruding area on the tire.

[0061] Figure 7 is a schematic diagram showing the airflow during vehicle travel near the road contact point on the axial outer surface of tire 1. The oblique grid area in Figure 7 indicates the area on the tire side surface 13 where the outer protrusion 31 is formed. The sandy area in Figure 7 indicates the area on the tire side surface 13 where the inner protrusion 41 is formed.

[0062] In a vehicle equipped with tire 1, when tire 1 rotates in the direction indicated by arrow α, the vehicle moves to the right in Figure 7, generating airflow in the direction indicated by arrow β from the front of the vehicle's direction of travel. At this time, near the road contact point of tire 1, the axial end of tire 1 tends to be compressed and bulge outwards. As a result, the air resistance near the road contact point of tire 1 increases, and the airflow tends to be swirled upwards as indicated by arrow γ. When this swirling increases, it collides with the air flowing in the longitudinal direction of the vehicle at the radial middle of tire 1. This makes it easier for the smooth airflow to the rear of the vehicle to be obstructed. In particular, when multiple protrusions are formed on the tire side surface, the air resistance near the road contact point of the tire increases even more, making it easier for the smooth airflow to the rear of the vehicle to be obstructed.

[0063] In this embodiment, as described above, a plurality of outer protrusions 31 are provided on the radially outer side of the tire side surface 13, arranged in the circumferential direction of the tire. Therefore, near the road contact point of the tire 1, the plurality of outer protrusions 31 are arranged in the longitudinal direction of the vehicle, as shown in Figure 4, and the height of the plurality of outer protrusions 31 changes in a mountain shape in the circumferential direction of the tire. As a result, air flows near the tire side surface 13, as shown by the arrow δ in Figure 8. In this case, compared to the case where the height of the plurality of outer protrusions is constant, the width of the negative pressure region generated downstream of the airflow of the plurality of outer protrusions 31 can be reduced. This reduces the pressure resistance caused by the formation of the outer protrusions 31, thereby suppressing the increase in air resistance during driving near the road contact point of the tire 1 and reducing turbulence. Therefore, air resistance during driving near the tire side surface 13 can be reduced.

[0064] Furthermore, near the vertical center on both sides of the tire side surface 13, as shown by the dashed-dotted frames B1 and B2 in Figure 7, multiple inner protrusions 41 are arranged in the vehicle's longitudinal direction, similar to the multiple outer protrusions 31 shown in Figure 8. In this case, similar to the multiple outer protrusions 31 near the road surface, the width of the negative pressure region generated downstream of the multiple inner protrusions 41 can be reduced compared to the case where the height of the multiple inner protrusions is constant. This reduces the pressure resistance caused by the formation of the inner protrusions 41, thereby suppressing the increase in air resistance during driving near the vertical center of the tire.

[0065] The spacing between the multiple protrusions in the outer protrusion group 30 and the inner protrusion group 40 is preferably equal, but it does not have to be equal. Also, the protrusion with the greatest height is preferably located in the center of each protrusion group, but it may be offset from the center.

[0066] Furthermore, in this embodiment, the outer projections 31 are provided on the side surfaces 7a, 7b of each shoulder block 2a, 2b, but they may also be provided only on every other shoulder block, for example, only on the side surface 7a of the shoulder block 2a that is located further outward in the tire axial direction.

[0067] Figure 9 shows the external shape of a projection 71 used as an outer or inner projection in a pneumatic tire of another embodiment. In this example, each projection 71 is a cylindrical pin, as shown in Figure 9, with a hemispherical portion that protrudes outward at its upper end. In this case, separation of the airflow at the edge of the upper end of each projection 71 can be suppressed, so the effect of suppressing the increase in air resistance becomes more pronounced. In this example, the other configurations and functions are the same as those in Figures 1 to 8.

[0068] Figure 10 is a diagram of a tire in another embodiment, corresponding to Figure 4. Figure 11 is a diagram of a tire in another embodiment, corresponding to Figure 5. Figure 12 is a diagram of a tire in another embodiment, corresponding to Figure 4, showing the airflow near the multiple outer protrusions 31a at the lower end.

[0069] As shown in Figure 10, the multiple outer protrusions 31a forming each outer protrusion group 30a are aligned in the circumferential direction of the tire, and the amount of protrusion changes in a valley shape from the first end to the second end in the circumferential direction of the tire. Furthermore, for the multiple outer protrusions 31a of the outer protrusion group 30a, it is preferable that the outer protrusions 31a at both ends, which have the maximum height, have a height of twice or less the height of the central outer protrusion 31a, which has the minimum height.

[0070] As shown in Figure 11, the multiple inner protrusions 41a forming each inner protrusion group 40a are aligned in the radial direction of the tire, and the amount of protrusion changes in a valley shape from the first end to the second end in the radial direction of the tire. Furthermore, for the multiple inner protrusions 41a of the inner protrusion group 40a, it is preferable that the height of the inner protrusions 41a at both ends, which have the maximum height, is twice or less the height of the central inner protrusion 41a, which has the minimum height.

[0071] In the alternative configuration described above, as shown in Figure 10, multiple outer protrusions 31a forming the outer protrusion group 30a are arranged in the longitudinal direction of the vehicle near the road contact point on the tire side surface 13. When the vehicle is in motion, air flows towards the rear of the vehicle near the tire side surface 13, as indicated by arrows η1, η2, and η3 in Figure 12. At this time, the height of the outer protrusions 31 on the front side of the vehicle gradually decreases toward the rear. As a result, air flows near the outer protrusions 31 on the front side of the vehicle as shown by arrow η1 in Figure 12. Therefore, similar to the case of the rear portion of the multiple outer protrusions 31 arranged in a V-shape as shown in Figure 8, the width of the negative pressure region generated downstream of the airflow of the multiple outer protrusions 31a can be reduced compared to the case where the height of the multiple outer protrusions is constant. Consequently, the pressure resistance due to the formation of the outer protrusions 31a can be reduced, and the increase in air resistance in the direction of vehicle travel near the road contact point of the tire can be suppressed.

[0072] Furthermore, the height of the multiple outer protrusions 31a forming the outer protrusion group 30a gradually increases from near the center of the vehicle in the longitudinal direction toward the rear. As a result, the air flowing in the direction of arrow η1 in Figure 12 is redirected to flow in the direction of arrow η2. In addition, turbulence is more likely to occur when the airflow hits the outer protrusions 31a that are taller in the area where the height of the outer protrusions 31a changes from decreasing to increasing. This turbulence generates a so-called downdraft that strikes the tire surface in a direction approximately perpendicular to it, making it easier to efficiently reduce the tire temperature from the tire surface. This makes it easier to reduce the temperature rise caused by the tire flexing near the contact patch.

[0073] Furthermore, near the vertical center on both sides of the tire side surface 13 in the longitudinal direction, multiple inner protrusions 41a are arranged in the longitudinal direction of the vehicle, similar to the multiple outer protrusions 31a shown in Figure 12. In this case, similar to the multiple outer protrusions 31a near the road contact point, the pressure resistance at the front portion of the multiple inner protrusions 41a can be reduced with respect to the airflow near the tire side surface 13 compared to the case where the height of the multiple inner protrusions is constant, thereby suppressing the increase in air resistance in the direction of vehicle travel near the vertical center of the tire.

[0074] Furthermore, the height of the multiple inner protrusions 41a that form the inner protrusion group 40a gradually increases from near the center of the vehicle in the longitudinal direction toward the rear. As a result, similar to the multiple outer protrusions 31a near the road contact point, turbulence is more likely to occur when the airflow hits the inner protrusions 41a that are taller in the area where the height of the inner protrusions 41a changes from decreasing to increasing. This makes it easier to efficiently reduce the tire temperature from the tire surface.

[0075] Furthermore, near the tire's maximum width, the rubber material forming the tire's surface is more easily deformed than the rubber material making up other parts of the tire. Therefore, as in this example, it is possible to easily mold tires that require larger protrusions of multiple inner protrusions 41a at both ends.

[0076] In this example, the configuration consists of multiple outer protrusions 31a of the outer protrusion group 30a and multiple inner protrusions 41a of the inner protrusion group 40a, which change to a valley shape in the circumferential or radial direction of the tire. This suppresses the increase in air resistance near the road contact point and near the vertical center of the tire, and also makes it easier to efficiently reduce the tire temperature. Although the effect of suppressing the increase in air resistance in this example is lower than that of the configurations in Figures 1 to 8, it is still more effective than the case where multiple protrusions of a constant protrusion height are provided on the tire side surface. In this example, the other configurations and functions are the same as those in Figures 1 to 8.

[0077] Furthermore, in each of the outer projection groups 30, 30a in the configuration of the above examples, multiple rows of outer projections 31, 31a arranged in the tire radial direction may be provided, and the amount of protrusion of each row of outer projections 31, 31a in the tire radial direction may be varied in a mountain-like or valley-like shape. Also, in each of the inner projection groups 40, 40a in the configuration of the above examples, multiple rows of inner projections 41, 41a arranged in the tire radial direction may be provided, and the amount of protrusion of each row of inner projections 41, 41a in the tire radial direction may be varied in a mountain-like or valley-like shape.

[0078] Furthermore, although the above examples describe the case where side blocks 5b are provided on the tire side surface, a configuration may also be provided where there are no side blocks on the tire side surface, and multiple outer protrusions and multiple inner protrusions are provided. In this case as well, similar to the above examples, the multiple inner protrusions are provided radially inward from the multiple outer protrusions on the tire side surface, and are arranged in the radial direction of the tire.

[0079] Furthermore, in the above embodiments, Figures 1 to 8 illustrate a tire 1 that combines a configuration in which the heights of multiple outer protrusions 31 of the outer protrusion group 30 are varied in a mountain shape, and a configuration in which the heights of multiple inner protrusions 41 of the inner protrusion group 40 are varied in a mountain shape. Furthermore, Figures 10 to 12 illustrate a tire that combines a configuration in which the heights of multiple outer protrusions 31a of the outer protrusion group 30a are varied in a valley shape, and a configuration in which the heights of multiple inner protrusions 41a of the inner protrusion group 40a are varied in a valley shape. On the other hand, the present invention is not limited to such configurations, and for example, a tire that combines a configuration in Figures 1 to 8 in which the heights of multiple outer protrusions 31 of the outer protrusion group 30 are varied in a mountain shape, and a configuration in Figures 10 to 12 in which the heights of multiple inner protrusions 41a of the inner protrusion group 40a are varied in a valley shape may also be used. Furthermore, a tire may be constructed by combining the configuration shown in Figures 10 to 12, in which the heights of the multiple outer protrusions 31a of the outer protrusion group 30a are varied in a valley shape, with the configuration shown in Figures 1 to 8, in which the heights of the multiple inner protrusions 41 of the inner protrusion group 40 are varied in a mountain shape. [Explanation of Symbols]

[0080] 1 pneumatic tire (tire), 2a,2b shoulder block, 2c,2d groove, 5 sidewall, 5a profile surface, 5b side block, 6 side rib, 7a,7b side, 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, 30,30a outer protrusions, 31,31a outer protrusions, 40,40a inner protrusions, 41,41a inner protrusions, 51 first side block, 52 second side block, 53 boundary, 61 first region, 62 second region, 63 third region, 64 convex portion, 65 slope, 71 protrusion, P tire maximum width position, T contact edge.

Claims

1. On the tire side surface, which is the outer surface in the tire axial direction, located radially inward from the tread contact edge and radially outward from the rim line, a plurality of outer protrusions are arranged in the circumferential direction of the tire and project outward from the tire surface, wherein at least some of the adjacent outer protrusions have different projection amounts, The tire side surface comprises a plurality of inner protrusions arranged radially inward from the plurality of outer protrusions in the tire radial direction, which protrude outward from the tire surface, and wherein at least some of the adjacent inner protrusions have different amounts of protrusion. Pneumatic tires.

2. The aforementioned multiple outer protrusions change in a mountain-like shape in the direction of the tire's circumference, The aforementioned plurality of inner protrusions have a protrusion amount that changes in a mountain shape in the direction of the tire's diameter. The pneumatic tire according to claim 1.

3. The aforementioned multiple outer protrusions change in a valley-like shape in the direction of the tire circumference, The aforementioned plurality of inner protrusions have a trough-shaped change in the amount of protrusion in the radial direction of the tire. The pneumatic tire according to claim 1.

4. The tire side surface comprises a plurality of shoulder blocks arranged in the circumferential direction of the tire, and a plurality of side blocks arranged in the circumferential direction of the tire, located radially inward from the plurality of shoulder blocks. The multiple outer protrusions are formed on the side surfaces of each of the multiple shoulder blocks that face outward in the tire axial direction. The plurality of inner protrusions are formed on the side surfaces of each of the plurality of side blocks that face outward in the tire axial direction. The pneumatic tire according to claim 1.

5. The shape of the base end of each of the aforementioned outer and inner protrusions, when viewed from the outside in the height direction, has a length ratio of 0.85 or more and 1.15 or less in mutually perpendicular directions. The pneumatic tire according to claim 1.

6. The shape of the base end of each of the aforementioned outer and inner protrusions, when viewed from the outside in the height direction, is circular. The pneumatic tire according to claim 5.

7. In each of the plurality of outer protrusions and the plurality of inner protrusions, the outer protrusion with the maximum height has a height of twice or less the height of the outer protrusion with the minimum height or the inner protrusion with the minimum height. The pneumatic tire according to claim 1.

8. The carcass is equipped with a belt layer located on the radially outer side of the tire, The belt layer includes a narrow belt and a wide belt whose length in the tire axial direction is greater than that of the narrow belt. The plurality of outer protrusions are formed on the outer surface of the tire, centered on a position that coincides with the outer end of the wide belt in the tire axial direction and the tire radial direction, within a tire radial length range corresponding to 5% to 15% of the tire cross-sectional height. The plurality of inner protrusions are formed on the outer surface of the tire within a tire radial length range corresponding to 10% to 35% of the tire cross-sectional height, centered on the tire radial position where the maximum tire width is defined. The pneumatic tire according to claim 1.

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