Pneumatic tire

Abstract

The utility model provides a pneumatic tire which comprises a bulge (30), and the bulge (30) is formed on a tire axial outer side surface, namely a tire side surface (13), which is closer to the radial inner side of the tire than a grounding end (T) of a tread part (10) and closer to the radial outer side of the tire than a rim assembly line (20). When viewed from the outside in the height direction, the shape of the root end of the projection (30) is a circular shape in which the length ratio between the longitudinal direction and the lateral direction, which are orthogonal to each other, is 0.85-1.15.

Description

Technical Field

[0001] The utility model relates to a pneumatic tire, and more particularly to a pneumatic tire with a protrusion formed on a tire side surface, wherein the tire side surface is an axially outer side surface of the tire which is closer to the outer side of the tire radial direction than a rim assembly line. Background Art

[0002] In recent years, the popularity of electric vehicles and hybrid vehicles has been rapidly developing, and with it, there is a strong demand to reduce the resistance to propulsion. One of the resistances is the air resistance when the vehicle is running. In order to reduce the air resistance on the side of the tire, although it is possible to consider removing the protrusions protruding from the side of the tire, there is still room for improvement from the perspective of improving the appearance of the tire.

[0003] On the other hand, in order to improve the appearance of the tire, although it is possible to consider setting hatching, grid patterns, serration patterns, etc. on the side of the tire, since it is easy to form a wall in the direction of air flow, it may cause increased air resistance.

[0004] Patent document 1 describes the following: on the surface of the tire side portion, a plurality of convex portions protruding toward the outside of the tire are regularly arranged, the maximum width and maximum height of the convex portions are within a specified range, and along the tire surface, the arrangement interval of the convex portions is greater than 0.1 μm and less than 100 μm. Patent document 1 states that, based on this, an optimal air relaxation layer can be formed on the tire surface.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2013-169827 Utility Model Content

[0008] In order to simultaneously improve the appearance of the tire and suppress the increase in air resistance when the vehicle is running, it is possible to consider setting the convex portion described in Patent Document 1 on the side of the tire. However, according to the tire described in Patent Document 1, the root end shape of the protrusion is not clear, and it may not be possible to fully obtain the effect of suppressing the increase in air resistance when the vehicle is running. In addition, when multiple protrusions arranged on the side of the tire are arranged close to each other, due to the shape of the protrusions, it may cause the tops of the multiple protrusions to become brighter and it is difficult to obtain the contrast of the side of the tire. Therefore, if considering improving the appearance of the tire, there is still room for improvement.

[0009] An object of the utility model is to provide a pneumatic tire which can simultaneously achieve improvement in tire appearance and suppression of increase in air resistance when a vehicle is traveling.

[0010] The pneumatic tire involved in the utility model has a protrusion, which is formed on the axially outer side of the tire, that is, the tire side surface, which is closer to the radial inside of the tire than the ground-contacting end of the tread portion (tread) and closer to the radial outside of the tire than the rim assembly line. The shape of the root end of the protrusion when observed from the outside in the height direction is a circle with a length ratio of mutually orthogonal directions, that is, longitudinal and lateral directions, being greater than 0.85 and less than 1.15.

[0011] According to the above-mentioned pneumatic tire, since the protrusions are provided on the side of the tire, the appearance can be improved. In addition, when a plurality of protrusions are arranged close to each other, the tops of the plurality of protrusions can be suppressed from becoming brighter, so that the contrast of the side of the tire can be obtained. Accordingly, the appearance of the tire can be further improved. In addition, when the vehicle is running, on the side of the tire, air can flow smoothly around the protrusions, so that the effect of suppressing the increase of air resistance can be obtained.

[0012] Utility Model Effect

[0013] The pneumatic tire of the utility model can simultaneously achieve: improving the appearance of the tire and suppressing the increase of air resistance when the vehicle is running. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a diagram showing a tire contour shape in a meridian cross section of a pneumatic tire as an example of an embodiment.

[0015] Figure 2 This is an enlarged perspective view of a protrusion according to an example of the embodiment.

[0016] Figure 3 It is observed from the outside in the height direction. Figure 2 Figure of the protrusion.

[0017] Figure 4 yes Figure 2 Magnified view of the surface of the protrusion.

[0018] Figure 5 This is a diagram showing a method for obtaining the average length Lm of elements on the surface roughness curve of the protrusions.

[0019] Figure 6 This is a schematic diagram showing that in the embodiment, after the air flow collides with the uneven surface roughness of the protrusion, the air flow re-attaches on the downstream side due to turbulence, so that the separation point is likely to be on the downstream side.

[0020] Figure 7 This is a schematic diagram showing that, in another example of the embodiment, when the average length roughness ratio on the surface roughness curve of the protrusion is less than 2, the protrusion surface does not generate turbulence like a smooth surface.

[0021] Figure 8 This is a schematic diagram showing that in another example of the embodiment, when the average length roughness ratio on the surface roughness curve of the protrusion is less than 2, a wake region caused by the separated air flow is generated on the downstream side of the air flow of the protrusion.

[0022] Fig. 9 This is a schematic diagram showing that in the embodiment, the width of the wake flow region caused by the separated air flow becomes narrower on the downstream side of the air flow relative to the protrusion, and the negative pressure reduction effect becomes higher.

[0023] Fig.10 This is a schematic diagram showing that, in the embodiment, when there are two protrusions close to each other, the area between the tops of the protrusions is darker as seen by a person observing the protrusions from the outside of the tire side surface.

[0024] Fig.11 FIG. 1 is a schematic diagram showing that, when there are two protrusions close to each other in a pneumatic tire of a comparative example, the area between the tops of the protrusions is brighter when viewed by a person observing the protrusions from the outside of the tire side surface. Fig.11 (a) is a view of the protrusion observed from the side orthogonal to the height direction. Fig.11 (b) is a diagram of the protrusion observed from the outside in the height direction.

[0025] Fig.12 It is a diagram showing a protrusion on a pneumatic tire according to another example of the embodiment.

[0026] Fig.13 It is a diagram showing a protrusion on a pneumatic tire according to another example of the embodiment.

[0027] Fig.14 It is a diagram showing a protrusion on a pneumatic tire according to another example of the embodiment.

[0028] Description of Reference Numerals

[0029] 1, 1a…pneumatic tire (tire); 10…tread portion; 12…sidewall portion; 13…tire side; 18…flange; 19…rim protector; 20…rim assembly line; 30, 30a, 30b, 30c, 30d, 30e…protrusion; 31…mountain; 32, 33…inclined edge; 34…curved portion; 40…wake region; T…ground contact end. DETAILED DESCRIPTION

[0030] Hereinafter, an example of an embodiment of the pneumatic tire involved in the utility model will be described in detail with reference to the accompanying drawings. The embodiment described below is only an example from beginning to end, and the utility model is not limited to the following embodiment. In addition, the selective combination of the various components of the multiple embodiments and modified examples described below is also included in the utility model.

[0031] Figure 1 FIG. 1 is a diagram showing a tire profile shape in a pneumatic tire 1 as an example of an embodiment. Figure 1 As shown, the pneumatic tire 1 includes: a tread portion 10 as a portion that contacts the road surface. Hereinafter, the "pneumatic tire 1" is referred to as "tire 1". The tread portion 10 has a tread pattern including a plurality of blocks, and is formed in an annular shape along the circumferential direction of the tire. In the illustrated example, although the tread portion 10 is shown to be formed by a single block, in fact, the tread portion 10 includes a plurality of blocks separated in the tire axial direction X. The plurality of blocks are separated by circumferential grooves extending along the circumferential direction of the tire. The tread portion 10 has a ground contact end T. Figure 1 In the figure, X represents the tire axial direction and Y represents the tire radial direction.

[0032] The configuration of the tire 1 is described below with the tire axial center CL as the center and the vehicle outer side (OUT side) as the center. The shape of the tire 1, except for the protrusions on the tire side described later, is symmetrical with the vehicle inner side.

[0033] The tire 1 includes: a sidewall 12, which is arranged at an end portion closer to the outer side of the tire axial direction X than the tread portion 10 and bulges most toward the outer side of the tire axial direction X; and a bead portion (not shown), which is fixed to the rim of the wheel. The sidewall portion 12 and the bead portion are formed into a ring shape along the tire circumferential direction. The sidewall portion 12 extends from both ends of the tread portion 10 in the tire axial direction X toward the inner side of the tire radial direction Y. A rim strip 18 is provided at the inner end portion of the tire 1 in the radial direction Y, which is adjacent to the sidewall portion 12 and forms the outer surface of the bead portion.

[0034] The tire 1 is a pneumatic tire filled with air at a predetermined pressure. The tread portion 10 is made of a tread rubber. The sidewall portion 12 is made of a sidewall rubber of a different type from the tread rubber.

[0035] In this specification, unless otherwise specified, the dimensions of each part of a tire refer to the dimensions measured in a normal state with no load, in which an unused tire is mounted on a normal rim and filled with air to a normal internal pressure.

[0036] The so-called "ground contact end T" refers to the two ends of the tire axial direction X in the area that contacts a flat road surface when a load of 88% of the normal load at the normal internal pressure is applied when an unused tire 1 is mounted on a normal rim and filled with air to achieve the normal internal pressure.

[0037] Here, the so-called "regular rim" refers to the rim determined by the tire specifications, which is the "standard rim" in JATMA, the "design rim" in TRA, and the "measurement rim" in ETRTO. Regarding the "regular internal pressure", it is the "maximum air pressure" in JATMA, the maximum value recorded in the table "Tire load limit at various cold inflation pressures" in TRA, and the "inflation pressure" in ETRTO. Regarding the "regular load", it is the "maximum load capacity" in JATMA, the maximum value recorded in the table "Tire load limit at various cold inflation pressures" in TRA, and the "load capacity" in ETRTO.

[0038] The tire 1 comprises: a carcass, a belt layer, and an inner liner. The carcass is a rubber-coated cord layer, which forms a skeleton of the tire 1 capable of withstanding loads, impacts, air pressure, etc. The belt layer is a reinforcing belt arranged between the tread rubber 11 and the carcass. The belt layer can strongly fasten the carcass and improve the rigidity of the tire 1. The belt layer is formed by overlapping a plurality of belts in the tire radial direction Y. A plurality of cords arranged in a direction inclined relative to the tire circumferential direction are coated with rubber to form each belt. In adjacent belts, the cords are inclined in opposite directions relative to the tire circumferential direction in such a manner that the cords cross each other. The cords are formed of steel or the like.

[0039] Between the belt layer and the tread rubber, there is provided a belt reinforcement layer extending in the tire circumferential direction and covering the entire belt layer in the tire axial direction X. The cord extending substantially in the tire circumferential direction is coated with rubber to form the belt reinforcement layer. The cord is formed of organic fibers or the like.

[0040] The tire 1 of the embodiment is specified in the mounting direction of the tire 1 with respect to the vehicle. That is, the tire 1 is specified to be the outer side and the inner side of the vehicle, respectively. Figure 1 In the embodiment, the tire 1 is mounted on the vehicle in such a manner that the right side is the outer side (OUT side) of the vehicle and the left side is the inner side (IN side) of the vehicle.

[0041] Generally, a mark called a serial number is provided on the side of the tire. The serial number includes information such as a size code, a manufacturing period (manufacturing year), and a manufacturing location (manufacturing plant code). The installation direction of the tire 1 relative to the vehicle is determined by providing the serial number only on the side of the tire (sidewall portion 12) facing the outside of the vehicle, or by providing different serial numbers on the side facing the outside of the vehicle and the side facing the inside of the vehicle. As a specific example, it can be cited that the manufacturing plant code and the size code are provided on both sides of the tire 1, and the manufacturing year is provided only on the side facing the outside in the vehicle width direction.

[0042] In addition, a display indicating that the tire is on the outer side of the vehicle in a mounted state on the vehicle with characters or symbols may be provided on the tire side facing the outer side of the vehicle.

[0043] In addition, as a part of the flap rubber forming the flap 18, there is provided a rim protector 19 protruding toward the outside of the tire axial direction. The rim assembly line 20 is provided in a ring shape along the circumference of the tire at the vertex of the rim protector 19 located at the outer end of the tire axial direction. The rim protector 19 has the function of protecting the rim from external damage. The rim assembly line 20 is a line that uses the gap between the rim and the wheel to confirm whether the tire 1 is assembled on the rim in the proper position. Figure 1 In the embodiment, although a rim protection member 19 is provided, Figure 1 As shown by the two-dot chain line, it is also possible to configure without the rim guard 19. Even in this case, a protrusion formed in an annular shape and protruding toward the tire axial outer side, i.e., a rim assembly line, is provided on the tire side for confirming whether the tire 1 is assembled on the rim in the proper position.

[0044] In this example, a plurality of protrusions 30 are provided on the tire side surface 13 which is located on the outer side in the tire radial direction Y than the ground contact end T of the tread portion 10 and on the outer side in the tire radial direction Y than the rim fitting line 20 .

[0045] The plurality of protrusions 30 are distributed and provided at a plurality of positions in the tire radial direction Y and at a plurality of positions in the tire circumferential direction.

[0046] Reference Figure 2 to Figure 4 , describing the structure of each protrusion 30. Figure 2 It is an enlarged perspective view of the protrusion 30 . Figure 3 This is a diagram of the protrusion 30 as viewed from the outside in the height direction Z. Figure 4 It is an enlarged view of the surface of the protrusion 30.

[0047] like Figure 2As shown in FIG. 1 , each protrusion 30 protrudes in a hemispherical shape from the tire side surface 13. Accordingly, the shape of the protrusion 30 viewed from the side perpendicular to the height direction Z and the cross-sectional shape along the height direction Z are as follows: Figure 4 As shown, the projection 30 is in a semicircular shape that is convex toward the outside and has a shape in which the lateral length decreases toward the end. The “lateral direction” is a direction perpendicular to the height direction Z of the projection 30 .

[0048] In addition, if Figure 3 As shown in FIG. 1 , the root end of each protrusion 30 is circular when viewed from the outside in the height direction. Here, the term "circular" means that the ratio of the lengths in the mutually orthogonal directions, i.e., the longitudinal direction and the lateral direction, is greater than 0.85 and less than 1.15. Figure 3 In FIG. 1 , the longitudinal direction is the direction of arrow A, and the lateral direction is the direction of arrow B. That is, when the longitudinal length is LA and the lateral length is LB, a shape satisfying 0.85≤LA / LB≤1.15 is defined as a "circular shape".

[0049] According to this, since the protrusions 30 are provided on the tire side 13, the appearance of the tire 1 can be improved by utilizing the contrast of the concave and convex. In addition, as described later, when the plurality of protrusions 30 provided on the tire side 13 are arranged close to each other, the tops of the plurality of protrusions 30 can be suppressed from becoming brighter, so that the contrast of the tire side can be obtained. According to this, the appearance of the tire 1 can be further improved. In addition, when the vehicle is running, on the tire side 13, as shown by arrows A1 and A2, the air can smoothly flow around the protrusions 30 along the curved shape of the outer periphery, so that the effect of suppressing the increase of air resistance can be obtained.

[0050] In addition, from the perspective of improving the appearance and suppressing the increase in air resistance, it is preferred that the average value ((LA+LB) / 2) of the longitudinal length LA and the lateral length LB in the shape of the root end of the protrusion 30 is greater than 0.5 mm and less than 5.0 mm, and the height of the protrusion 30 is greater than 0.8 times and less than 1.5 times the average value. On the other hand, in a case where the above average value ((LA+LB) / 2) is less than 0.5 mm, the effect of improving the appearance will be reduced. In a case where the above average value ((LA+LB) / 2) exceeds 5.0 mm, the effect of suppressing the increase in air resistance will be reduced. In a case where the height of the protrusion 30 is less than 0.8 times the above average value, the effect of improving the appearance will be reduced. In a case where the height of the protrusion 30 exceeds 1.5 times the above average value, the effect of suppressing the increase in air resistance will be reduced.

[0051] In addition, if Figure 4As shown, tiny concavo-convex shapes are formed on the surface of the protrusion 30, and due to the concavo-convex shapes, the surface of the protrusion 30 will present an appropriate surface roughness. Accordingly, as described later, when the protrusion 30 is observed from the outside, an appropriate turbulent boundary layer of the air flow is easily formed near the surface. As a result, the position where the air flow peels off from the protrusion 30 can be shifted further toward the downstream side. As a result, the width of the wake region formed on the wake side of the protrusion 30 and where the speed of the air flow decreases can be reduced, thereby further suppressing the increase in the air resistance of the tire 1.

[0052] Specifically, the ratio (Lm / Rzjis) of the average length Lm of the elements on the roughness curve of the surface of the protrusion 30 to the ten-point average roughness Rzjis as the concave-convex height, that is, the average length roughness ratio is 2 or more and 6 or less. Figure 5 The method for calculating the average length Lm of the elements on the surface roughness curve of the protrusion 30 is shown. The so-called "average length Lm" is the average value of the element lengths in the reference length of the roughness curve. The so-called "reference length" is a portion of a certain length cut out from the roughness curve in order to calculate the roughness parameters such as the ten-point average roughness.

[0053] Specifically, if Figure 5 As shown, in the surface roughness curve of the protrusion 30, it is possible to consider intercepting: a reference length (arbitrarily set within the range of 0.5 mm to 5 mm) Lx in the direction along the average line LG of the concave-convex height. In this case, taking the average line LG of the intercepted portion as a reference, the portion that exceeds the average line LG on the upper side is set as a mountain, and the portion that becomes lower by exceeding the average line LG on the lower side is set as a valley, and the portion formed by one continuous mountain and one valley is set as one element of one cycle. Moreover, the value obtained by dividing the sum of the lengths of the average lines of the elements along the 1st cycle to the Nth cycle in the reference length Lx, that is, L1, L2...LN, by the number of cycles N is determined as the average length Lm of the element. That is, Lm = (L1+L2+L3+...+LN) / N.

[0054] The method for measuring the ten-point average roughness Rzjis can be in accordance with: JIS B0601:2001 based on ISO4287-1987. Specifically, when solving the ten-point average roughness Rzjis, in the above-mentioned cut-off portion, regarding the height calculated from the average line LG, the absolute value of the average value of the heights of the five mountains from the mountain with the highest vertex to the mountain with the fifth highest vertex calculated from the average line LG can be solved. In addition, in the above-mentioned cut-off portion, regarding the lowness calculated from the average line LG, the absolute value of the average value of the lowness of the five valleys from the valley with the lowest valley point to the valley with the fifth lowest valley point calculated from the average line LG can be solved. The sum of the absolute value of the above-mentioned average value of the height and the absolute value of the average value of the lowness is: the ten-point average roughness Rzjis.

[0055] Figure 6 : It is a schematic diagram showing that in the embodiment, after the air flow indicated by the arrow α collides with the surface roughness of the protrusion 30, the air flow reattaches on the downstream side due to turbulence, making the separation point easy to become the downstream side. Figure 6 As shown, in the embodiment, since the above-mentioned average length roughness ratio is greater than 2 and less than 6, the air flow after colliding with the tiny uneven hills 31 on the surface of the protrusion 30 will become turbulent and flow toward the downstream side, and the turbulent flow will collide with the hills 31 on the downstream side again and repeat. Accordingly, the stripping point of the air flow at the surface of the protrusion 30 is easily offset to the downstream side. Thus, as described later, the width of the wake area that is formed on the downstream side of the protrusion 30 and becomes a negative pressure by the stripping flow of the air stripped from the stripping position of the protrusion 30 from the part sandwiched from both sides can be reduced. Thus, the pressure resistance caused by the formation of the protrusion 30 can be reduced, and therefore, the increase in air resistance can be further suppressed.

[0056] Figure 7 : A schematic diagram showing that in another example of the embodiment, when the average length roughness ratio on the surface roughness curve of the protrusion 30a is less than 2, the surface of the protrusion 30a does not generate turbulence like a smooth surface. Figure 7 As shown in FIG. 1 , the density of the tiny concavo-convexities per unit area on the surface of the protrusion 30a becomes higher. Accordingly, the surface of the protrusion 30a becomes the same as a smooth surface due to the relationship with the air flow shown by the arrow α, so it is difficult to generate turbulence in the air flow. As a result, it is difficult to produce the effect that the separation point of the air flow at the surface of the protrusion 30a is shifted to the downstream side. Therefore, the effect of reducing the negative pressure is reduced, and therefore, the effect of suppressing the increase of air resistance is reduced.

[0057] On the other hand, when the average length-to-roughness ratio exceeds 6, the amount of concavity and convexity formed on the protrusion surface decreases, and thus the negative pressure reduction effect decreases. In this case, the effect of suppressing the increase in air resistance also decreases.

[0058] In addition, the arithmetic mean roughness Ra of the surface of the protrusion 30 may be configured to be 0.40 μm or more and 1.60 μm or less when the measurement reference length is 0.25 mm, or 3.2 μm or more and 6.3 μm or less when the measurement reference length is 2.5 mm. The arithmetic mean roughness Ra may be measured in accordance with JIS B 0601:2001 based on ISO4287-1987.

[0059] In addition, the plurality of protrusions 30 may be configured to be formed on the tire side surface 13 within a tire radial direction Y range of 25% or more and 60% or less when the tire radial direction position of the rim assembly line 20 or the tire axial outer end of the rim protector 19 is set to 0 and the tire cross-sectional height Ht is set to 100 ( Figure 1 within the range indicated by the arrow β).

[0060] According to this configuration, the protrusion 30 can be provided on the tire side surface 13 from the tire axial outer end ( Figure 1 The range starts from the part near P) toward the outer side of the tire radial direction Y, which is easily contacted by the air flow, to the outer peripheral side of the tire that is easy to be noticed and has a higher effect of improving the appearance.

[0061] The protrusion 30 can be formed by performing hole processing on the inner surface of a mold used for tire molding. For example, as the hole processing, NC processing using a cutting tool such as an end mill, laser processing, or electric discharge machining can be adopted.

[0062] use Figure 8 , Fig. 9 , further describing the effects of the implementation method in detail. Figure 8 : A schematic diagram showing a wake region caused by the separated air flow generated on the downstream side of the air flow beyond the protrusion 30a when the average length roughness ratio on the surface roughness curve of the protrusion 30a is less than 2 in another example of the embodiment. Figure 8 In the embodiment, a large amount of turbulence is formed inside the wake region 40 .

[0063] exist Figure 8In the other examples shown, since the above-mentioned average length roughness ratio is less than 2, as described above, the surface of the protrusion 30a does not generate turbulence like the smooth surface. In this case, it can be imagined that the air flow shown by the dotted line will hit the protrusion 30a as the tire rotates when the vehicle is running. In this case, positive pressure is generated on the upstream side of the air flow of the protrusion 30, so that the protrusion 30a is pressed toward the downstream side. Moreover, when the air flow flows from the upstream side of the protrusion 30a along the surface of the protrusion 30a to the downstream side, the air flow will Figure 8 The air is peeled off from the surface of the protrusion 30a at the C1 and C2 positions. The air is peeled off from the peeling position of the protrusion 30a to form a negative pressure wake area 40 from the part sandwiched on both sides. Figure 8 In the case of Figure 8 The length in the vertical direction of the projection 30a increases, and therefore, the effect of reducing the negative pressure decreases. As a result, the pressure resistance caused by the projection 30a increases, and therefore, the effect of suppressing the increase in air resistance decreases.

[0064] Fig. 9 : A schematic diagram showing that in the embodiment, the width of the wake region 40 caused by the separated air flow becomes narrower and the negative pressure reduction effect becomes higher at the downstream side of the air flow relative to the protrusion 30. Fig. 9 As shown, in the embodiment, since the above-mentioned average length roughness ratio is greater than or equal to 2 and less than or equal to 6, according to the use of Figure 6 For the reasons described above, the separation point where the air flow separates from the surface of the protrusion 30 is easily shifted to the downstream position, that is, C3 and C4. Accordingly, the width of the wake flow region 40 formed by the portion sandwiched from both sides by the separation flow of the air separated from the separation position of the protrusion 30 on the downstream side of the protrusion 30 and becoming a negative pressure can be reduced. As a result, the pressure resistance caused by the formation of the protrusion 30 can be reduced, and thus the increase in air resistance can be further suppressed.

[0065] Fig.10: A schematic diagram showing that, in the embodiment, when there are two protrusions 30 close to each other, the tops of the protrusions 30 viewed by a person observing the protrusions 30 from the outside of the tire side surface are dark. In the embodiment, the shape of the root end when the protrusions 30 are observed from the outside in the height direction is a circle whose length ratio in the mutually orthogonal directions, i.e., the longitudinal direction and the lateral direction, is 0.85 or more and 1.15 or less. Accordingly, when the plurality of protrusions 30 provided on the tire side surface 13 are arranged close to each other, when light is irradiated onto the protrusions 30 as indicated by arrows D1 and D2 and the position of the light deviates from the viewpoint E of the person in the surface direction of the tire side surface, the reflection direction of the light deviates from the viewpoint E easily. At the same time, the light reflected between the tops of the protrusions 30 on the tire side surface is difficult to be directed to the viewpoint E. In particular, since the surface of the protrusion 30 is spherical, the light is reflected in various directions on the surface of the protrusion 30 and is more difficult to be directed to the viewpoint E of the person. As a result, it is possible to suppress the tops of the plurality of protrusions 30 from becoming brighter, and thus it is possible to obtain a contrast on the tire side surface. This can improve the appearance of the tire 1 .

[0066] Fig.11 Yes: A schematic diagram showing that, in the pneumatic tire 1a of the comparative example, when there are two protrusions 30b close to each other, the area between the tops of the protrusions 30b is brighter as viewed by a person observing the protrusions 30b from the outside of the tire side surface. Fig.11 (a) is a view of the protrusion 30b observed from the side orthogonal to the height direction, Fig.11 (b) is a diagram showing the protrusion 30b as viewed from the outside in the height direction.

[0067] like Fig.11 As shown in (b), in the comparative example, the shape of the protrusion 30b observed from the outside in the height direction is a water drop shape with a pointed tip. Fig.11 As shown in (a), the shape of the protrusion 30b when viewed from the side perpendicular to the height direction is likely to be a roughly triangular mountain shape in terms of formability. In such a comparative example, when two protrusions 30b are arranged close to each other, the length of the gently inclined surface of the side surface of the protrusion 30b becomes longer. Fig.11 As shown in (a), when the position of light deviates from the viewpoint E of the person in the surface direction of the tire side, as shown by arrows D3 and D4, the light reflected from the side of the protrusion 30b tends to be closer to the viewpoint E of the person. As a result, the tops of the plurality of protrusions 30E become brighter, and therefore, it may be difficult to obtain the contrast of the tire side. Based on this, there is still room for improvement from the perspective of improving the appearance of the tire 1a. In the embodiment, as shown in Fig.10 As described above, such a disadvantage can be solved.

[0068] In the embodiment, the shape of the protrusion 30 viewed from the side perpendicular to the height direction is semicircular. In addition, the cross-sectional shape of the protrusion 30 along the height direction is a shape in which the lateral length decreases toward the end. Accordingly, when the protrusion 30 is formed by hole processing in the mold used in tire molding, the inner surface of the hole can be made into a hemispherical surface. Thus, the hole can be easily formed in the mold by mechanical processing or laser processing using a cutting tool.

[0069] In the above-described embodiment, the case where the shape of the protrusion 30 viewed from the side perpendicular to the height direction is a semicircular shape has been described. However, in the present invention, the protrusion is not limited to such a shape. Figure 12 to Figure 14 Three examples of protrusions on a pneumatic tire according to other examples of the embodiment are shown.

[0070] First, about Fig.12 The protrusion 30c of the first example of the other example shown in the figure has a shape of a trapezoidal shape or a truncated cone shape having inclined sides 32 on both sides in the lateral direction. Figure 3 The protrusions 30 shown are likewise circular.

[0071] about Fig.13 The protrusion 30d of the second example of the other example shown in the figure has a shape of a substantially rectangular or cylindrical shape when viewed from the side. Figure 3 The protrusions 30 shown are likewise circular.

[0072] about Fig.14 The protrusion 30e of the third example of the other example shown in the figure has a shape viewed from the side that is a mountain shape having inclined sides 33 on both sides in the lateral direction and connecting curved portions 34 having an arc portion at the upper end and convex toward the outside. The shape of the protrusion 30e viewed from the outside in the height direction is similar to Figure 3 The protrusions 30 shown are likewise circular.

[0073] about Fig.12 as well as Fig.14 The protrusions 30c and 30e of the other example shown are Figures 1 to 4 Similarly to the protrusion 30 of the embodiment shown, the cross-sectional shape of the protrusions 30c and 30e along the height direction is a shape with inclined sides whose lateral length decreases toward the end. Accordingly, when the protrusions 30c and 30e are formed by hole processing in the mold used for tire molding, the inner surface of the hole can be made into a tapered surface whose inner diameter decreases toward the inner side. Thus, the hole can be easily formed in the mold by mechanical processing or laser processing using a cutting tool.

[0074] In the above-described embodiment, the protrusions are formed only on the tire side surface 13 facing the outer side of the vehicle. However, the protrusions may be formed on the tire side surfaces on both sides of the vehicle without specifying the tire mounting direction.

Claims

1. A pneumatic tire, the pneumatic tire having a protrusion formed on: an axially outer side of the tire, i.e., a side surface of the tire, which is closer to the inner side of the tire radial direction than the ground contact end of the tread portion and closer to the outer side of the tire radial direction than the rim assembly line, characterized in that: The shape of the base end of the protrusion when viewed from the outside in the height direction is a circle with a length ratio of the longitudinal direction to the lateral direction orthogonal to each other being 0.85 or more and 1.15 or less.

2. The pneumatic tire according to claim 1, characterized in that The ratio Lm / Rzjis of the average length Lm of the elements on the roughness curve of the surface of the protrusion to the ten-point average roughness Rzjis as the concavo-convex height H, that is, the average length roughness ratio is 2 or more and 6 or less.

3. The pneumatic tire according to claim 1 or 2, characterized in that: The average value of the longitudinal length and the lateral length of the root end of the protrusion is 0.5 mm or more and 5.0 mm or less, The height of the protrusions is not less than 0.8 times and not more than 1.5 times the average value.

4. The pneumatic tire according to claim 1 or 2, characterized in that: The arithmetic mean roughness Ra of the surface of the protrusion is 0.40 μm or more and 1.60 μm or less when the measurement reference length is 0.25 mm, or is 3.2 μm or more and 6.3 μm or less when the measurement reference length is 2.5 mm.

5. The pneumatic tire according to claim 1 or 2, characterized in that: The protrusion is formed in the tire side surface within a tire radial range of 25% to 60% when the tire radial position of the tire axial outer end of the rim fitting line or the rim protector is set to 0 and the tire cross-sectional height is set to 100.

6. The pneumatic tire according to claim 1 or 2, characterized in that: The cross-sectional shape of the protrusion along the height direction is a shape in which the lateral length decreases toward the distal end.

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