Pneumatic tire

Abstract

The utility model provides a pneumatic tire which comprises a plurality of protrusions (30), and the protrusions (30) are formed on a tire axial outer side face, namely a tire side face (13), which is closer to the radial inner side of the tire than a grounding end (T) of a tread portion (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 protrusion (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. When the average length of the longitudinal length and the lateral length in the shape of the root ends of the protrusions is set to be phi, the interval between adjacent protrusions in the tire circumferential direction is set to be L, and the height of the protrusions is set to be H, the protrusion reference length-height ratio (phi + L) / H is 2-6.

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 that a plurality of cylindrical protrusions are provided that protrude from the surface of the sidewall of the tire and generate turbulence. Patent Document 1 states that turbulence can be generated by the edge of the connection portion between the end surface of the protrusion and the sidewall surface.

[0005] Patent Document 2 describes the following: On the surface of the tire side portion, a plurality of protrusions protruding toward the outside of the tire are regularly arranged, the maximum width and maximum height of the protrusions are within a specified range, and along the tire surface, the protrusions are arranged at intervals greater than 0.1 μm and less than 100 μm. Patent Document 2 states that, based on this, an optimal air relaxation layer can be formed on the tire surface.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: International Publication No. 2008 / 096879

[0009] Patent Document 2: Japanese Patent Application Publication No. 2013-169827 Utility Model Content

[0010] In order to simultaneously improve the appearance of the tire and suppress the increase in air resistance when the vehicle is running, it is conceivable to set the protrusions described in Patent Document 1 or Patent Document 2 on the side of the tire. However, according to the tires described in Patent Document 1 and Patent Document 2, due to the relationship between the size of the root end shape of the protrusion, the height of the protrusion and the spacing between the protrusions, it is possible that the effect of suppressing the increase in air resistance cannot be fully obtained. In addition, when multiple protrusions set on the side of the tire are arranged closely, due to the shape of the protrusions, it is possible that the tops of the multiple protrusions 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.

[0011] 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.

[0012] The pneumatic tire involved in the utility model has a plurality of protrusions, and the plurality of protrusions are formed on: the axially outer side of the tire, that is, the 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 (tread) and closer to the outer side of the tire radial direction 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 ratio of lengths in mutually orthogonal directions, that is, longitudinal and lateral directions, being greater than 0.85 and less than 1.15. When the average length of the longitudinal length and the lateral length in the shape of the root end of the protrusion is set to φ, the interval between the protrusions adjacent to each other in the tire circumferential direction is set to L, and the height of the protrusion is set to H, the protrusion reference length height ratio (φ+L) / H is greater than 2 and less than 6.

[0013] According to the above-mentioned pneumatic tire, since the protrusions are provided on the side of the tire, it is possible to achieve an improvement in appearance. In addition, the relationship between the size of the root end shape of the protrusion, the height of the protrusion, and the spacing between the protrusions is optimized from the perspective of improving the appearance and suppressing the increase in air resistance. Accordingly, it is possible to simultaneously achieve an improvement in appearance and suppress the increase in air resistance. In addition, when a plurality of protrusions are arranged close to each other, it is possible to suppress the tops of the plurality of protrusions from becoming brighter, thereby reducing the sense of incongruity brought to people observing the side of the tire. Accordingly, it is possible to achieve a further improvement in the appearance of the tire.

[0014] Effect of utility model

[0015] 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

[0016] Figure 1It is a diagram showing a tire contour shape in a meridian cross section of a pneumatic tire as an example of an embodiment.

[0017] Figure 2A It is observed from the outside of the tire axis. Figure 1 A three-dimensional view of a circumferential portion of a tire.

[0018] Figure 2B This is a diagram showing a portion in the tire circumferential direction as viewed from the tire axially outer side in a first example of other examples of arrangement of the protrusions.

[0019] Figure 2C This is a diagram showing a portion in the tire circumferential direction as viewed from the tire axially outer side in a second example of other examples of arrangement of the protrusions.

[0020] Figure 3 This is an enlarged perspective view of a protrusion according to an example of the embodiment.

[0021] Figure 4 It is observed from the outside in the height direction. Figure 3 Figure of the protrusion.

[0022] Figure 5 This is a schematic diagram for explaining the dimensional relationship between two protrusions arranged in the tire circumferential direction according to an example of the embodiment.

[0023] Figure 6 This is a schematic diagram showing that in an embodiment, after the air flow hits a protrusion, the air flow is attached to another protrusion on the downstream side due to turbulence, so that the separation point is likely to be on the downstream side.

[0024] Figure 7 This is a schematic diagram showing that in a comparative example in which the protrusion reference length height ratio is less than 2, the surfaces of the plurality of protrusions on the tire side surface do not generate turbulence similarly to a smooth surface.

[0025] Figure 8 This is a schematic diagram showing a wake region caused by separated airflow generated on the downstream side of the airflow from the tire side in a comparative example in which the protrusion reference length height ratio is less than 2, using a cylinder Sa to simulate.

[0026] Fig. 9 This is a schematic diagram showing that in the embodiment, the cylinder S is used to simulate the air flow separated from the air flow downstream of the tire side, and the width of the wake flow region becomes narrower and the negative pressure reduction effect becomes higher.

[0027] 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 as seen by a person observing the protrusions from the outside of the tire side surface is darker.

[0028] 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.

[0029] Fig.12 It is a diagram showing a protrusion on a pneumatic tire according to another example of the embodiment.

[0030] Fig.13 It is a diagram showing a protrusion on a pneumatic tire according to another example of the embodiment.

[0031] Fig.14 It is a diagram showing a protrusion on a pneumatic tire according to another example of the embodiment.

[0032] Fig.15 This is a diagram showing a plurality of protrusions on a pneumatic tire according to another example of the embodiment as viewed from the outside in the height direction.

[0033] Fig.16 It is a diagram showing a protrusion on a pneumatic tire according to another example of the embodiment.

[0034] Description of Reference Numerals

[0035] 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; 50, 51…protrusion; T…ground contact end. DETAILED DESCRIPTION

[0036] 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.

[0037] Figure 1 It is a diagram showing a tire profile shape in a pneumatic tire 1 as an example of the embodiment. Figure 2A This is a three-dimensional view of a portion of the circumferential direction of the tire 1 as viewed from the axially outer side of the tire. Figure 1As 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 , Figure 2A In the figure, X represents the tire axial direction and Y represents the tire radial direction.

[0038] The following description will focus on the tire axial center CL and the vehicle outer side (OUT side) portion as the configuration of the tire 1. With respect to the tire 1 contour shape, the vehicle outer side portion and the vehicle inner side portion of the tire 1 are symmetrical, except for the protrusions on the tire side described later.

[0039] The tire 1 includes: a sidewall portion 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] like Figure 1 , Figure 2A As shown, 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 .

[0051] The plurality of protrusions 30 are distributed at a plurality of positions in the tire radial direction Y and are distributed at a plurality of positions in the tire circumferential direction. Figure 2A As shown, the plurality of protrusions 30 are dispersedly arranged on a plurality of concentric circles having different diameters, and the protrusions 30 are formed at a plurality of positions in the tire circumferential direction on each circle. The protrusions 30 on the plurality of circles are arranged side by side in the tire radial direction Y.

[0052] The arrangement of the plurality of protrusions 30 is not limited to Figure 2A Configuration. Figure 2B 1 is a diagram showing a portion of the tire circumferential direction viewed from the tire axially outer side in another example of the arrangement of the protrusions. Figure 2B As shown, when viewed from the outside of the tire axial direction, the plurality of protrusions 30 may be arranged in a so-called staggered configuration, that is, they are dispersed on a plurality of concentric circles of different diameters, and the positions of the protrusions 30 on adjacent circles in the tire circumferential direction R are staggered by 1 / 2 pitch. Figure 2A In the arrangement example, the positions of the plurality of protrusions arranged every other protrusion in the radial direction Y and located on a circle match each other in the tire circumferential direction.

[0053] Figure 2C : In the second example of another example of the arrangement of the protrusions, a portion of the tire circumferential direction is viewed from the tire axial outer side. Figure 2C As shown, the plurality of protrusions 30 are dispersedly arranged on a plurality of concentric circles having different diameters when viewed from the tire axially outer side. However, the plurality of protrusions 30 may be arranged so as not to be opposed in the tire radial direction Y.

[0054] Reference Figure 3 to Figure 5 , describing the structure of each protrusion 30 and the arrangement of the plurality of protrusions 30 . Figure 3 It is an enlarged perspective view of the protrusion 30 . Figure 4 This is a diagram of the protrusion 30 as viewed from the outside in the height direction Z. Figure 5 It is a schematic diagram for explaining the dimensional relationship between two protrusions 30 arranged in the tire circumferential direction.

[0055] like Figure 3 As 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 5 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 .

[0056] In addition, if Figure 4 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 4 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".

[0057] 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.

[0058] 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 0.3 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 0.3 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.

[0059] In addition, in the embodiment, if Figure 5 As shown, when the average length of the longitudinal length and the lateral length in the shape of the root end of the protrusion 30 is φ, the interval between the protrusions 30 adjacent to each other in the tire circumferential direction is L, and the height of the protrusion 30 is H, the protrusion reference length height ratio, i.e., (φ+L) / H, is greater than 2 and less than 6. Accordingly, the position where the air flow is peeled off from the tire side 13 can be shifted further toward the downstream side, i.e., the rear side in the tire travel direction. Thus, the width of the wake area formed on the downstream side of the air flow of the tire 1 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.

[0060] Figure 6 : It is a schematic diagram showing that in the embodiment, after the air flow indicated by the arrow α hits the protrusion 30 on the tire side 13, the air flow is attached to another protrusion 30 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 protrusion reference length-to-height ratio is greater than 2 and less than 6, the air flow after hitting the protrusion 30 on the tire side 13 will become turbulent and move toward the downstream side, and the turbulent flow will hit another protrusion 30 on the downstream side again and repeat. Accordingly, the separation point of the air flow at the tire side 13 is easily shifted to the downstream side. As a result, as described later, the width of the wake area formed by the part sandwiched from both sides by the separation flow of the air separated from the separation position of the tire side 13 and becoming a negative pressure on the downstream side of the air flow of the tire can be reduced. As a result, 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.

[0061] Figure 7: A schematic diagram showing that in a comparative example where the protrusion reference length to height ratio 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 plurality of protrusions 30a per unit area on the tire side surface becomes higher. Accordingly, the tire side surface becomes the same as a smooth surface due to the relationship with the air flow indicated by the arrow α, so it is difficult to generate turbulence in the air flow. As a result, it is difficult to generate the effect that the separation point of the air flow at the tire side surface 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.

[0062] On the other hand, when the protrusion reference length-to-height ratio exceeds 6, the amount of protrusions formed on the tire side surface decreases, and thus the negative pressure reduction effect decreases. In this case, the effect of suppressing the increase in air resistance also decreases.

[0063] 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).

[0064] 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.

[0065] 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.

[0066] 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 a separated air flow generated on the downstream side of the air flow from the tire side in a comparative example where the protrusion reference length-to-height ratio is less than 2, using a cylinder Sa to simulate. Figure 8 In the embodiment, a large amount of turbulence is formed inside the wake region 40. Figure 8 , Fig. 9 , a cylinder Sa is shown to be used to simulate a tire.

[0067] exist Figure 8 In the other examples shown, since the protrusion reference length to height ratio is less than 2, as described above, the tire side does not generate turbulence like the smooth surface. In this case, it can be imagined that as the tire rotates while the vehicle is running, the air flow shown by the dotted line will collide with the surface of the cylinder Sa that is the tire side. In this case, positive pressure is generated on the upstream side of the air flow of the cylinder Sa, so that the cylinder Sa is pressed toward the downstream side. Moreover, when the air flow flows from the upstream side of the cylinder Sa along the surface of the cylinder Sa to the downstream side, the air flow will Figure 8 The air is separated from the surface of the cylinder Sa at the positions C1 and C2. The air separation flow separated from the separation position of the cylinder Sa forms a negative pressure wake region 40 from the portion sandwiched on both sides. Figure 8 In the case of Figure 8 Therefore, when the protrusion reference length height ratio is less than 2, the effect of suppressing the increase of the pressure resistance of the tire is reduced, and therefore, the effect of suppressing the increase of the air resistance is reduced.

[0068] Fig. 9 : A schematic diagram showing a cylinder S used to simulate the narrowing of the width of the wake region 40 and the enhancement of the negative pressure reduction effect caused by the air flow separated from the tire side in the embodiment. Fig. 9 In the figure, a small protrusion formed on the surface of a cylinder S is used to simulate that a plurality of protrusions 30 are formed on the tire side surfaces on both sides of the tire axial direction.

[0069] like Fig. 9 As shown, in the embodiment, since the above-mentioned protrusion reference length height ratio is greater than 2 and less than 6, according to the use of Figure 6 The reason explained is that the separation point where the air flow separates from the tire side is easily shifted to the downstream side, that is, C3 and C4. Based on this, the width of the wake area 40 formed by the separation flow of the air separated from the separation point on the surface of the cylinder S and forming a negative pressure on the downstream side of the cylinder S simulating the tire can be reduced. Fig. 9 In the embodiment, although it is simulated that a plurality of protrusions 30 are formed on the tire side surface on both sides of the tire axial direction, as in the embodiment, even if a plurality of protrusions 30 are formed only on the tire side surface on the outer side of the vehicle, the width of the wake region 40 will be reduced. Accordingly, in the embodiment, since the effect of suppressing the increase in the pressure resistance of the tire is improved, the increase in air resistance can be further suppressed.

[0070] 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 .

[0071] 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.

[0072] 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. In addition, the shape of the root end of the protrusion 30b when observed from the outside in the height direction is a shape in which the ratio of the lengths in the mutually orthogonal directions, i.e., the longitudinal direction and the lateral direction, i.e., LA1 / LB1, is less than 0.85. In such a comparative example, 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.11As 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.

[0073] 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.

[0074] 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.

[0075] 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 4 The protrusions 30 shown are likewise circular.

[0076] 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 4 The protrusions 30 shown are likewise circular.

[0077] 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 4 The protrusions 30 shown are likewise circular.

[0078] about Fig.12 as well as Fig.14The 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.

[0079] Fig.15 This is a view of a plurality of protrusions 50 of a tire according to another embodiment as viewed from the outside in the height direction. Fig.15 In the structure shown, each protrusion 50 is in the shape of a triangular pyramid, and the root end of the protrusion 50 when viewed from the outside in the height direction is in the shape of a triangle with a length ratio LA2 / LB2 of the longitudinal direction to the lateral direction orthogonal to each other being 0.85 or more and 1.15 or less. Fig.15 In the embodiment, the plurality of protrusions 50 are arranged at a plurality of positions in the tire circumferential direction with gaps on each of the plurality of circles with different diameters. In addition, on each circle, the configuration sides of the ends J of the adjacent protrusions 50 in the tire circumferential direction are opposite.

[0080] In addition, the protrusions 50 on the plurality of circles are arranged in the tire radial direction at a plurality of tire circumferential positions. The protrusions 50 on the plurality of circles at the same tire circumferential position are arranged in the tire radial direction. In addition, the ends J of the protrusions 50 adjacent to each other in the tire radial direction among the protrusions 50 on the plurality of circles are arranged on opposite sides in the tire circumferential direction.

[0081] Even other examples such as Fig.10 As shown, similar to the case where the shape of the protrusion 30 observed from the outside in the height direction is circular, when the position of light deviates from the viewpoint of a person in the surface direction of the tire side, the light is easily reflected in many different directions on the side of the triangular pyramid-shaped protrusion 50. Accordingly, the reflection direction of the light is easily deviated from the viewpoint. At the same time, the light reflected between the tops K of the protrusions 50 on the tire side will be difficult to be directed toward the viewpoint. In addition, the distance between the tops K of the protrusions 50 can be reduced. Thus, it is possible to suppress the tops K of multiple protrusions 50 from becoming brighter, so that the contrast of the tire side can be obtained. Accordingly, it is possible to achieve an improvement in the appearance of the tire.

[0082] In addition, the shape of the protrusions provided on the side of the tire is not limited to these shapes, and may also be a triangular prism, a quadrangular prism, a pentagonal prism or other polygonal prism, or a quadrangular pyramid, a pentagonal pyramid or other polygonal pyramid. Fig.16Like the protrusion 51 of the other example shown, the protrusion 51 provided on the tire side surface may be in a shape in which a hemispherical portion is provided at the end of a cylindrical portion.

[0083] In the above-mentioned embodiment, the case where the protrusion reference length height ratio (φ+L) / H is greater than or equal to 2 and less than or equal to 6 is described using the interval L of the protrusions adjacent to each other in the tire circumferential direction. On the other hand, in the embodiment, the protrusion reference length height ratio (φ+L) / H may be obtained using the interval L of the protrusions adjacent to each other in a direction different from the tire circumferential direction, such as the tire radial direction. Moreover, the protrusion reference length height ratio thus obtained may also be greater than or equal to 2 and less than or equal to 6.

[0084] In the above embodiment, the plurality of protrusions 30, 50 provided on the tire side are provided in the tire radial direction Y and in the tire circumferential direction. On the other hand, the plurality of protrusions may be provided at a plurality of positions in the tire circumferential direction on a single circle having a constant diameter.

[0085] 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, comprising a plurality of protrusions, wherein the plurality of protrusions are 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 root 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. When the average length of the longitudinal length and the lateral length in the shape of the root end of the protrusion is set to φ, the interval between the protrusions adjacent to each other in the tire circumferential direction is set to L, and the height of the protrusion is set to H, the protrusion reference length height ratio (φ+L) / H is greater than 2 and less than 6.

2. The pneumatic tire according to claim 1, characterized in that The average length φ of the protrusions is greater than or equal to 0.3 mm and less than or equal to 5.0 mm, and the height H of the protrusions is greater than or equal to 0.8 times and less than or equal to 1.5 times the average length φ.

3. The pneumatic tire according to claim 1 or 2, characterized in that: The root end of the protrusion is in a circular or triangular shape.

4. 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.

5. 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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