Pneumatic tire and pneumatic tire mold

Abstract

To provide a pneumatic tire which enables reduction of air resistance in a structure which has a plurality of ridges arranged in a tire circumferential direction on a tire side surface.SOLUTION: A tire which is one example of an embodiment includes a plurality of ridges 30 which are streaked projections formed on a tire side surface that is an outward surface in a tire axial direction located further inward in a tire radial direction than a ground contact end of a tread and further outward in the tire radial direction than a rim line. Each ridge extends outward in the tire radial direction in a range which inclines by 60 degrees to both sides in the tire circumferential direction with a direction along the tire radial direction of the tire side surface 13 set as a center. A ratio L / H of a distance L between centers of tops of the adjacent ridges 30 and a height H of the ridge is 2 or more and 6 or less.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire and a mold for molding a pneumatic tire, and more particularly to a pneumatic tire having ridges, which are multiple streak-like protrusions, formed on the tire side surface, which is the axially outer surface of the tire radially outward from the rim line. [Background technology]

[0002] In recent years, the provision of ridges, which are multiple stripe-like protrusions, on tire sidewalls has been considered to improve tire design and the visibility of tire sidewall markings. For example, Patent Document 1 describes a configuration in which multiple ridges are arranged in a predetermined region of a tire sidewall to improve the visibility and cleaning performance of the tire sidewall. In this configuration, the multiple ridges are parallel to one another and periodically protrude from the base surface, and the range of the length Lb of one cycle of the multiple ridges along the base surface is regulated in relation to the length Lr of one cycle along the ridge profile in a cross-sectional view of the ridges. Patent Document 1 also states that the hydrophilicity of the ridges can be improved by setting the arithmetic mean roughness of the rubber on the ridge surface to be 0.1 μm or more and 5 μm or less. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-24435 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for reducing tire air resistance while improving tire design. Providing multiple ridges on the tire side, as in the configuration described in Patent Document 1, may potentially improve tire design. However, simply restricting the length of one ridge cycle in relation to the length along the ridge contour, or restricting the surface roughness of the ridge, as in the configuration described in Patent Document 1, does not provide the expected effect of reducing air resistance by suppressing air separation. Therefore, there is room for improvement in achieving a tire that can reduce air resistance in a configuration with multiple ridges aligned circumferentially on the tire side surface.

[0005] An object of the present invention is to provide a pneumatic tire and a mold for molding the same that can reduce air resistance in a configuration having a plurality of ridges aligned in the tire circumferential direction on the tire side surface. [Means for solving the problem]

[0006] The pneumatic tire of the present invention is a pneumatic tire having a plurality of ridges, which are stripe-like protrusions, arranged regularly around the tire circumferential direction on the tire side surface, which is the axially outer surface of the tire, radially inward from the ground-contact edge of the tread and radially outward from the rim line, each of which extends radially outward in the tire direction within a range inclined by 60 degrees on both sides of the tire circumferential direction, with the direction along the tire radial direction of the tire side surface as its center, and a ratio L / H of the center-to-center distance L of the peaks of adjacent ridges to the height H of the ridge, which is 2 or more and 6 or less.

[0007] The pneumatic tire mold according to the present invention is a pneumatic tire mold for molding the pneumatic tire according to the present invention, and has a plurality of recesses on the molding surface corresponding to the plurality of ridges. [Effects of the Invention]

[0008] According to the pneumatic tire and mold for molding a pneumatic tire according to the present invention, air resistance can be reduced in a pneumatic tire having a plurality of ridges aligned in the tire circumferential direction on the tire side surface. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing a tire contour shape in a meridian cross section of a pneumatic tire that is an example of an embodiment, and is a diagram showing the ranges in which a plurality of ridges are formed. FIG. [Figure 2] 1 is a view of a part in the tire circumferential direction of a pneumatic tire according to an embodiment, viewed from the outside in the tire axial direction. [Figure 3] FIG. 2 is a perspective view showing a partially cutaway annular portion where a ridge is formed in the embodiment. [Figure 4] FIG. 2 is an enlarged cross-sectional view of part A in FIG. [Figure 5] FIG. 10 is a schematic diagram showing that, after an airflow collides with a ridge, turbulence causes the airflow to reattach to another ridge downstream, and the separation point is likely to be located downstream in an embodiment. [Figure 6] FIG. 10 is a schematic diagram showing that in a comparative example in which the ridge interval height ratio is less than 2, the surface of a tire side surface including ridges does not generate turbulence, just like a smooth surface. [Figure 7] FIG. 1 is a schematic diagram showing, using a cylinder Sa as a simulation, the occurrence of a wake region due to separated airflow downstream of the tire side surface in the airflow in a comparative example in which the ridge spacing height ratio is less than 2. [Figure 8] FIG. 10 is a schematic diagram illustrating, using a cylinder S as a simulation, how the width of the wake region caused by the separated air flow narrows downstream of the tire side surface in the air flow, increasing the negative pressure reduction effect in an embodiment. [Figure 9] FIG. 10 is a diagram showing a method for determining the average length Lm of elements in the surface roughness curve of a ridge in an embodiment. [Figure 10] FIG. 2 is a cross-sectional view showing a mold for molding a pneumatic tire in an embodiment. [Figure 11] FIG. 10 is a diagram showing a peak portion and a valley portion having different arithmetic mean roughnesses of the surface, using the cross-sectional shape of a ridge, in a pneumatic tire according to another embodiment. [Figure 12]FIG. 10 is a view showing a part of a plurality of ridges on a tire side surface in the tire circumferential direction as viewed from the tire axially outer side in another example of an embodiment, with the tire circumferential direction extended laterally. [Figure 13] FIG. 10 is a view of a portion of a plurality of ridges on a tire side surface in the tire circumferential direction as viewed from the outer side in the tire axial direction in another example of the embodiment. [Figure 14] 10A and 10B are diagrams illustrating a cross-sectional shape of a ridge in a pneumatic tire according to another embodiment. [Figure 15] 10A and 10B are diagrams illustrating a cross-sectional shape of a ridge in a pneumatic tire according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

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

[0011] FIG. 1 is a diagram showing the tire contour shape in a meridian cross section of a pneumatic tire 1 according to an embodiment, illustrating the ranges in which multiple ridges are formed. As shown in FIG. 1, the pneumatic tire 1 includes a tread 10, which is the portion that comes into contact with the road surface. Hereinafter, the "pneumatic tire 1" will be referred to as the "tire 1." The tread 10 has a tread pattern including multiple blocks, and is formed in an annular shape along the tire circumferential direction. In the illustrated example, the tread 10 is shown as being formed of a single block, but in reality, the tread 10 includes multiple blocks separated in the tire axial direction X. The multiple blocks are separated by circumferential grooves extending in the tire circumferential direction. The tread 10 has a ground contact edge T. In FIG. 1, the tire axial direction is indicated by X, and the tire radial direction is indicated by Y.

[0012] Hereinafter, the configuration of the tire 1 will be described mainly on the vehicle outer side (OUT side) of the tire 1 with respect to the center CL in the tire axial direction X. The tire 1 is symmetrical between the vehicle outer side and the vehicle inner side with respect to the shape other than the annular portion 100 on which a ridge is provided on the tire side surface, which will be described later.

[0013] The tire 1 includes a sidewall 12 that is provided at an end on the outer side of the tread 10 in the tire axial direction X and bulges outward most in the tire axial direction X, and a bead (not shown) that is fixed to a wheel rim. The sidewall 12 and the bead are formed in an annular shape along the tire circumferential direction. The sidewall 12 extends inward in the tire radial direction Y from both ends of the tread 10 in the tire axial direction X. A rim strip 18 that forms the outer surface of the bead is provided adjacent to the sidewall 12 at the inner end of the tire 1 in the radial direction Y.

[0014] The tire 1 is a pneumatic tire filled with air at a predetermined pressure. The tread 10 is made of tread rubber. The sidewall 12 is made of a different type of sidewall rubber than the tread rubber.

[0015] In this specification, unless otherwise specified, the dimensions of each part of a tire are dimensions measured when an unused tire is mounted on a standard rim, inflated to the standard internal pressure, and in a standard, unloaded state.

[0016] "Touching edge T" refers to both ends in the axial direction X of the tire in the area that comes into contact with a flat road surface when an unused tire 1 is mounted on a standard rim, inflated to the standard internal pressure, and subjected to a load that is 88% of the standard load at the standard internal pressure.

[0017] Here, a "regular rim" is a rim specified by the tire standard, and is a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. "Regular internal pressure" is the "maximum air pressure" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "INFLATION PRESSURE" for ETRTO. "Regular load" is the "maximum load capacity" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "LOAD CAPACITY" for ETRTO.

[0018] The tire 1 comprises a carcass, a belt layer, and an inner liner. The carcass is a cord layer covered with rubber, and forms the skeleton of the tire 1 that can withstand loads, impacts, air pressure, etc. The belt layer is a reinforcing band disposed between the tread rubber 11 and the carcass. The belt layer tightens the carcass to increase the rigidity of the tire 1. The belt layer is formed by overlapping multiple belts in the tire radial direction Y. Each belt is formed by multiple cords arranged in a direction inclined relative to the tire circumferential direction and covered with rubber. The cords of adjacent belts are inclined in opposite directions relative to the tire circumferential direction so that they cross each other. The cords are formed from steel or the like.

[0019] A belt reinforcing layer is provided between the belt layer and the tread rubber, extending in the tire circumferential direction and covering the entire belt layer in the tire axial direction X. The belt reinforcing layer is formed by covering cords extending substantially in the tire circumferential direction with rubber. The cords are made of organic fibers or the like.

[0020] In the tire 1 of the embodiment, the mounting direction of the front and back of the tire 1 on the vehicle is specified. That is, the outer and inner sides of the vehicle are respectively specified for the tire 1. In Fig. 1, the tire 1 is mounted on the vehicle so 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.

[0021] A symbol called a serial number is generally provided on the side of a tire. The serial number includes information such as a size code, manufacturing date (manufacturing year and week), and manufacturing location (manufacturing factory code). The mounting direction of the tire 1 on the vehicle can be specified by providing a serial number only on the tire side (sidewall 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. A specific example is to provide a manufacturing factory code and a size code on both sides of the tire 1, and provide the manufacturing year and week only on the side facing the outside of the vehicle width direction.

[0022] In addition, a marking such as a letter or symbol may be provided on the side of the tire facing outward from the vehicle to indicate that the tire is on the outside when mounted on the vehicle.

[0023] Furthermore, a rim protector 19 that protrudes axially outward is provided as part of the rim strip rubber that forms the rim strip 18. The rim line 20 is provided in an annular shape along the circumferential direction of the tire at the apex of the rim protector 19 that is located at the axially outer end of the tire. The rim protector 19 has the function of protecting the rim from external damage. The rim line 20 is a line that can be used to check the gap between the tire 1 and the rim to ensure that the tire 1 is properly mounted on the rim. Although the rim protector 19 is provided in Figure 1, the configuration may also be such that the rim protector 19 is not provided, as indicated by the two-dot chain line in Figure 1. Even in this case, a rim line, which is a circular protrusion that protrudes axially outward, is provided on the side of the tire to ensure that the tire 1 is properly mounted on the rim.

[0024] In this example, an annular portion 100 including multiple ridges 30 is provided on the tire side surface 13, which is the outer surface in the tire axial direction X, located inside the ground contact edge T of the tread 10 in the tire radial direction Y and outside the rim line 20 in the tire radial direction Y.

[0025] FIG. 2 is a view of a portion of a tire 1 according to an embodiment in the tire circumferential direction, as viewed from the tire axially outer side. As shown in FIG. 2, an annular portion 100 having a constant length in the tire radial direction is provided on a tire side surface 13 facing the vehicle outer side. The annular portion 100 is formed by a plurality of ridges 30, which are streak-like protrusions arranged at equal intervals in the tire circumferential direction, protruding axially outward from an annular recessed portion 37. Each ridge 30 extends in the tire radial direction. Each ridge 30 has the same shape. As will be described later, the tire of the present invention may be configured to include, instead of the annular portion 100 and the annular recessed portion 37, an arc-shaped portion and an arc-shaped recessed portion, each formed by a plurality of ridges arranged in the tire circumferential direction and provided at one or more positions in the tire circumferential direction of the tire side surface.

[0026] 3 is a perspective view showing a partially cutaway annular portion 100 in which the ridges 30 are formed in the embodiment. The multiple ridges 30 are arranged in an annular recess 37 provided along the tire circumferential direction in the tire side surface 13. The annular recess 37 is recessed from the sidewall reference plane 14 (FIGS. 2 and 3) toward the tire inner surface, with approximately the same depth and the same tire radial width, all around the tire circumferential direction.

[0027] The sidewall reference surface 14 means the surface of the tire side surface 13 facing outward in the tire axial direction of the sidewall 5 in a portion where partial irregularities such as protrusions of side blocks or recesses are not formed.

[0028] The multiple ridges 30 protrude axially outward from the bottom surface 38 of the annular recess 37 and are aligned at equal intervals in the tire circumferential direction. The bottom surface 38 is a protrusion formation reference surface and is part of the tire side surface 13. The cross-sectional view of the portion of the bottom surface 38 from which each ridge 30 rises can be a straight line. "Also aligned at equal intervals" means that the intervals between adjacent ridges 30 at the same radial position of the tire are uniform among the multiple ridges 30. As a result, the multiple ridges 30 are aligned regularly in the tire circumferential direction.

[0029] Each ridge 30 has a triangular cross section perpendicular to the extension direction, and is continuous in the tire radial direction, which is the extension direction, with approximately the same cross section. As a result, each ridge 30 extends radially outward in the tire direction within a range inclined by 60 degrees on both sides in the tire circumferential direction, with the tire radial direction of the tire side surface 13 as the center.

[0030] Both ends of each ridge 30 in the extension direction are connected to the wall surfaces of both ends in the tire radial direction of the annular recess 37. The cross-sectional shape of each ridge 30 can be an isosceles triangle that is symmetrical on both sides in the tire circumferential direction with respect to the center of each ridge 30 in the tire circumferential direction.

[0031] Fig. 4 is an enlarged cross-sectional view of part A in Fig. 1. As shown in Figs. 3 and 4, the height H of each ridge 30 is slightly greater than the depth D from the opening end 39 to the bottom surface 38 of the annular recess 37. As a result, the vicinity of the ridge line 31, which is the top of each ridge 30, protrudes outward beyond the opening end 39 of the annular recess 37.

[0032] 4, the height H of the ridge 30 is, for example, 0.3 mm or more and 1.1 mm or less. Meanwhile, the depth D of the annular recess 37 is 0.2 mm or more and 1.0 mm or less, and the ridge 30 protrudes outward from the opening end 39 of the annular recess 37 by 0.1 mm or more. In this way, a portion of the ridge 30 protrudes outward from the opening end 39 of the annular recess 37, which can emphasize the presence of the ridge 30 from the outside, thereby improving the design of the tire side surface 13.

[0033] Returning to FIG. 3, the width W of the ridge 30 in the tire circumferential direction, which is a direction perpendicular to the extension direction of the ridge 30, is 1.5 to 3.5 times the height H of the ridge 30.

[0034] Furthermore, the ridge interval height ratio L / H, which is the ratio of the distance L between ridge lines 31, which is the distance between the centers of the tops of adjacent ridges 30, to the height H of the ridge 30, is equal to or greater than 2 and equal to or less than 6. In this example, since each ridge 30 extends in the tire radial direction, the distance L between ridge lines increases from the inner side toward the outer side in the tire radial direction. Even in this case, the ridge interval height ratio L / H is equal to or greater than 2 and equal to or less than 6 throughout the extension direction of the ridges 30. This makes it possible to reduce the air resistance of the tire 1 while suppressing a deterioration in appearance.

[0035] FIG. 5 is a schematic diagram showing that, in an embodiment, after an airflow indicated by an arrow α collides with a ridge 30 on the bottom surface 38, turbulence causes the airflow to reattach to another ridge 30 downstream, making the separation point more likely to shift downstream. In this embodiment, the ridge-to-height ratio L / H is greater than or equal to 2 and less than or equal to 6, so that the airflow that collides with the ridge 30 on the bottom surface 38 becomes turbulent and heads downstream. This turbulent flow then collides again with another ridge 30 downstream, and so on. This makes it more likely that the separation point of the airflow on the tire side surface 13 will shift downstream. Therefore, as described below, the width of the wake region, which is formed by the portion of the separated airflow from the separation position on the tire side surface 13 on the downstream side of the airflow of the tire and experiences negative pressure, can be reduced. This reduces the pressure resistance caused by the formation of the ridge 30, thereby suppressing an increase in air resistance.

[0036] FIG. 6 is a schematic diagram showing that in a comparative example in which the ridge interval height ratio L / H is less than 2, the surface of the tire side surface including the ridges 30a is less likely to generate turbulence, similar to a smooth surface. When the ridge interval height ratio L / H is less than 2, as shown in FIG. 6, the density of the multiple ridges 30a per unit area of ​​the tire side surface is high. This makes the tire side surface similar to a smooth surface in relation to the airflow indicated by the arrow α, making it less likely to generate turbulence in the airflow. This makes it less likely that the separation point of the airflow on the tire side surface will shift downstream. This reduces the effect of reducing negative pressure, thereby reducing the effect of suppressing increases in air resistance.

[0037] On the other hand, if the ridge interval height ratio L / H exceeds 6, the amount of ridges 30 formed on the tire side surface 13 decreases, reducing the effect of reducing negative pressure. In this case as well, the effect of suppressing an increase in air resistance decreases.

[0038] The effects of the embodiment will be described in more detail with reference to Figures 7 and 8. Figure 7 is a schematic diagram showing, by simulating a cylinder Sa, the generation of a wake region 40 due to a separated airflow downstream of the tire side surface 13 in the airflow in a comparative example in which the ridge interval height ratio is less than 2. In Figure 7, many turbulent flows are formed inside the wake region 40. In Figures 7 and 8, the tire is shown simulated by the cylinder Sa.

[0039] In the comparative example shown in FIG. 7 , the ridge interval height ratio is less than 2, so turbulence does not occur on the tire side surface 13, similar to a smooth surface, as described above. Consider the case where an airflow, indicated by a broken line, collides with the surface of the cylinder Sa, which serves as the tire side surface 13, as the tire rotates during vehicle travel. In this case, a positive pressure is generated on the airflow upstream side of the cylinder Sa, pushing the cylinder Sa downstream. Then, as the airflow flows downstream along the surface of the cylinder Sa from the airflow upstream side of the cylinder Sa, it separates from the surface of the cylinder Sa at positions C1 and C2 in FIG. 13 . A wake region 40, where negative pressure exists, is formed in the area sandwiched between the separated air flows from the separation position of the cylinder Sa. In the case of FIG. 7 , the width (vertical length in FIG. 7 ) of this wake region 40 is large, so the negative pressure reduction effect is small. Therefore, when the ridge interval height ratio is less than 2, the effect of suppressing an increase in pressure resistance in the tire is low, and therefore the effect of suppressing an increase in air resistance is also small.

[0040] 8 is a schematic diagram illustrating, in an embodiment, a cylinder S simulating that the width of the wake region 40 caused by the separated air flow narrows downstream of the tire side surface 13 in the air flow, thereby enhancing the negative pressure reduction effect. In FIG. 8, the formation of multiple ridges 30 on the tire side surface 13 on both sides in the tire axial direction is simulated by minute protrusions formed on the surface of the cylinder S.

[0041] As shown in FIG. 8 , in this embodiment, the ridge spacing height ratio is between 2 and 6, both inclusive. This means that the separation point of the airflow from the tire side surface 13 is more likely to shift to downstream positions C3 and C4, for the reasons explained in FIG. 5 . This reduces the width of the wake region 40, which is formed on the downstream side of the cylinder S simulating a tire and is sandwiched between the separated airflows from the separation point on the surface of the cylinder S, and which experiences negative pressure. While FIG. 8 simulates the formation of multiple ridges 30 on the tire side surface 13 on both axial sides of the tire, the width of the wake region 40 is also reduced even in cases where multiple ridges 30 are formed only on the tire side surface 13 on the vehicle outer side, as in this embodiment. As a result, in this embodiment, the effect of suppressing an increase in pressure resistance in the tire is enhanced, thereby suppressing an increase in air resistance.

[0042] Furthermore, in this embodiment, minute irregularities are formed on the surface of each ridge 30, and these irregularities provide the surface of the ridge 30 with an appropriate surface roughness. This makes it easier to form an appropriate turbulent boundary layer for the airflow near the surface of the ridge 30 on the tire side surface. This makes it possible to shift the position at which the airflow separates from the ridge 30 further downstream. This reduces the width of the wake region formed on the wake side of the ridge 30, where the airflow speed is reduced, thereby further suppressing an increase in the air resistance of the tire 1.

[0043] Specifically, the roughness pitch ratio, which is the ratio (Lm / Rzjis) of the average length Lm of elements in the surface roughness curve of the ridges 30 to the ten-point mean roughness Rzjis, which is the height of the irregularities, is between 2 and 6. Figure 9 shows a method for determining the average length Lm of elements in the surface roughness curve of the ridges 30. The "average length Lm" is the average value of the element lengths in the reference length of the roughness curve. The "reference length" is a portion of a certain length that is extracted from the roughness curve in order to determine roughness parameters such as the ten-point mean roughness.

[0044] Specifically, as shown in FIG. 9, a reference length Lx (set arbitrarily within the range of 0.5 mm to 5 mm) along the direction of the mean line LG of the height of the irregularities is extracted from the surface roughness curve of the ridge 30. In this case, a continuous portion consisting of one peak, which is a portion that exceeds the mean line LG above the extracted portion, and one continuous valley, which is a portion that exceeds the mean line LG below the mean line LG, is considered to be one element of one period. The average length Lm of the element is then determined by dividing the sum of L1, L2, ... LN, which are the lengths along the mean line of the elements from the first period to the Nth period in the reference length Lx, by the number of periods N. That is, Lm = (L1 + L2 + L3 + + LN) / N.

[0045] The ten-point average roughness Rzjis is measured according to JIS B 0601:2001, which conforms to ISO 4287-1987. Specifically, the ten-point average roughness Rzjis is calculated by calculating the absolute value of the average height from the mean line LG of the five peaks in the sampled area, from the peak with the highest peak to the peak with the fifth highest peak. The absolute value of the average height from the mean line LG of the five valleys in the sampled area, from the valley with the lowest valley point to the valley with the fifth lowest valley point, is also calculated. The sum of the absolute values ​​of the average heights and the absolute values ​​of the average valley depths is the ten-point average roughness Rzjis. In this example, the roughness pitch ratio (Lm / Rzjis), which is the ratio of the average length Lm of the elements to the ten-point average roughness Rzjis, which is the height of the irregularities, is 2 or more and 6 or less. This reduces the width of the wake region formed on the wake side of the ridge 30 where the airflow speed is reduced, thereby further suppressing an increase in the air resistance of the tire 1.

[0046] In addition, in an embodiment, the multiple ridges 30 may be configured to be formed on the tire side surface 13 within a tire radial direction Y range (within the range indicated by arrow β in FIG. 1 ) of 5% to 65% when the tire radial direction position of the rim line 20 is set to 0 and the tire cross-sectional height Ht is set to 100.

[0047] With this configuration, the ridge 30 can be provided in a range from the vicinity of the tire axial outer end (P in Figure 1) of the tire side surface 13 corresponding to the maximum tire width, that is, the outer portion in the tire radial direction Y, where the air flow is likely to hit, to the outer peripheral portion of the tire where it is easily noticeable and has a great effect in improving the design.

[0048] Furthermore, the cross-sectional shape of the ridge 30 in this example along the height direction is a triangle with an inclined side whose horizontal length decreases toward the tip. This allows the inner surface of the groove to have a tapered surface whose width decreases toward the back when the ridge 30 is formed by groove processing in a mold used for tire molding. This makes it easier to form the groove in the mold using machining with a cutting tool or laser processing.

[0049] Fig. 10 is a cross-sectional view showing a tire molding mold of an embodiment. The tire 1 of this embodiment is formed using a tire molding mold 70. Hereinafter, the tire molding mold 70 will be referred to as the mold 70. The mold 70 is a mold that molds the tire 1 shown in Figs. 1 to 5 described above. The mold 70 makes it possible to realize a tire 1 that has a plurality of ridges 30 aligned in the tire circumferential direction on the tire side surface 13 and that can reduce air resistance.

[0050] Hereinafter, each member will be described in accordance with the tire axial direction X and tire radial direction Y of the tire 1 molded by the mold 70.

[0051] The mold 70 has a tread mold 71 for molding the surface of the tread of the tire 1, and a pair of side molds 72 for molding the surfaces of the sidewalls.

[0052] The tread mold 71 has a body 74 having a tread molding surface 73 and a protrusion 75 protruding from the tread molding surface 73 .

[0053] The main body 74 is made of a metal material, for example, an aluminum alloy. As the aluminum alloy, for example, AC4 series, AC7 series, etc. are preferably used. The protrusions 75 are portions that form circumferential grooves in the tire 1. The protrusions 75 are made of the same material as the metal material that makes up the main body 74.

[0054] The side mold 72 has a main body 76 with side molding surfaces 77a, 77b, and the side molding surface 77a, which forms the tire side surface on the outer side of the vehicle, has an annular protrusion 78 that protrudes outward from the side molding surface 77a. The main body 76 is made of the same metal material as the main body 74. The annular protrusion 78 is a part that forms the annular recess 37 (FIGS. 3 and 4) in the tire 1, where multiple ridges 30 protrude from the bottom surface 38.

[0055] The tread mold 71 has a fan shape in a plan view, formed by dividing an annular body into multiple parts in the circumferential direction. The multiple divided tread molds 71 ​​form a continuous annular body with an inner diameter corresponding to the outer diameter of the tire 1 to be molded when in a clamped state, as described below. The upper side mold 72 is annular and fixed to the lower surface of an upper plate (not shown) constituting the vulcanization molding machine, and moves up and down as a first lifting member (not shown) moves up and down. The lower side mold 72 is annular and fixed to the floor surface and to the lower surface of a lower plate (not shown) constituting the vulcanization molding machine. The vulcanization molding machine raises and lowers multiple segments (not shown), one for each tread mold 71, outside the multiple divided tread molds 71, using a first lifting member. Simultaneously with the raising and lowering of the first lifting member, the vulcanization molding machine slides the inclined surfaces of the outer peripheral surfaces of the multiple segments up and down on an inclined cylindrical surface provided at the lower end of a second lifting member (not shown) that moves up and down independently of the first lifting member. As a result, the vulcanization molding machine reciprocates the multiple segments in the radial direction relative to the central axis of the annularly continuous tread mold 71. As a result, the vulcanization molding machine switches the mold 70 between a mold clamped state and a mold open state.

[0056] In the mold 70 configured in this manner, a green tire is placed on the lower tread mold 71 with the tire axial direction aligned vertically when the mold is open. An inflatable bladder is then placed inside the green tire, and air is supplied to the bladder to inflate it. Then, with the inner surface of the green tire held by the outer surface of the bladder, the first lifting member and the second lifting member are raised and lowered to close the mold 70. The rubber of the green tire is pressed against the tread molding surface 73 and side molding surfaces 77a, 77b by the pressure from the mold 70, and a heat exchange medium adjusted to a predetermined temperature is constantly flowing between the member fixing the upper plate and the member fixing the lower plate. This vulcanizes the rubber of the green tire, completing a tire 1 with a predetermined shape.

[0057] In this embodiment, an annular protrusion 78 for molding an annular recessed portion 37 from which multiple ridges 30 protrude is formed on a side molding surface 77a for forming the tire side surface 13 on the vehicle outer side. A top surface 78a of the annular protrusion 78 corresponds to the bottom surface 38 of the annular recessed portion 37. Furthermore, multiple recessed portions 80 corresponding to the multiple ridges 30 provided on the tire side surface 13 are formed at multiple positions around the circumference of the annular protrusion 78. The recessed portions 80 are recessed in the shape of a groove extending from the top surface 78a with a substantially triangular cross section.

[0058] The multiple recesses 80 of the mold can be formed by groove machining on the top surface 78a of the annular protrusion 78 of the mold. For example, NC machining using a cutting tool such as an end mill, laser machining, or electric discharge machining can be used for the groove machining.

[0059] According to the tire 1 and mold 70 described above, air resistance can be reduced in the tire 1 having the plurality of ridges 30 aligned in the tire circumferential direction on the tire side surface 13.

[0060] Fig. 11 is a diagram showing a peak portion 81 and a valley portion 82 having different arithmetic mean roughnesses on the surface, using the cross-sectional shape of a ridge 30a in a tire according to another embodiment. As shown in Fig. 11, in the configuration of this example, the peak portion 81 and the valley portion 82 of each ridge 30a have different surface roughnesses. Specifically, when the peak portion 81 is located above the ridge 30a at the center C in the height H direction and the valley portion 82 is located below the ridge 30a, the arithmetic mean roughness of the surface of the valley portion 82 on both sides in the width direction is smaller than the arithmetic mean roughness of the surface of the peak portion 81 on both sides in the width direction. Even in this case, the arithmetic mean roughness of the surface of each of the peak portion 81 and the valley portion 82 of the ridge 30a is preferably 1.3 µm or more and 1.9 µm or less.

[0061] According to the configuration of this example, the arithmetic mean roughness of the surface of the valley-side portion 82 is smaller than the arithmetic mean roughness of the surface of the peak-side portion 81. As a result, when the ridges 30a are arranged diagonally relative to the vertical direction or horizontally depending on the rotation of the tire while the vehicle is running, it is possible to reduce the air resistance of air passing inside the valley-side portion 82, which is the side of the peak-side portion 81 and the valley-side portion 82 where air resistance is likely to be large. This further reduces the air resistance of the tire. In this example, the other configurations and functions are the same as those of the configurations shown in Figures 1 to 5 and 10.

[0062] 12 is a view of a portion of the tire circumferential direction of multiple ridges 30b on a tire side surface 13 in another example of the embodiment, as viewed from the tire axially outer side, with the tire circumferential direction extended laterally. In the configuration of this example, the multiple ridges 30b provided in the annular recess 37 of the tire side surface 13 are inclined toward one side in the tire circumferential direction (the right side in FIG. 12) toward the tire radially outer side with respect to the tire radial direction. In FIG. 12, only the ridge line of each ridge 30b is shown.

[0063] The multiple ridges 30b protrude axially outward from the bottom surface 38 of the annular recess 37 and are arranged at equal intervals around the tire. In this example, "arranged at equal intervals" also means that the intervals between adjacent ridges 30b at the same radial position of the tire are uniform among the multiple ridges 30b.

[0064] Furthermore, each ridge 30b extends radially outward in the tire direction at an angle θa within a range inclined by 60 degrees to one side in the tire circumferential direction, with the direction along the tire radial direction of the tire side surface 13 as its center (for example, the direction along the dashed-dotted line La in FIG. 12 ). In FIG. 12 , each ridge 30 is inclined at an angle θa of approximately 60 degrees to one side in the tire circumferential direction with the direction along the tire radial direction as its center, but the inclination angle may be 10 degrees, 20 degrees, 30 degrees, or the like. In this example, too, the ratio L / H of the distance L between the ridge lines at the centers of the peaks of adjacent ridges 30 to the height H of the ridge 30 is 2 or more and 6 or less throughout the entire extension direction of the ridge 30. In this example, the other configurations and functions are the same as those shown in FIGS. 1 to 5 and 10 .

[0065] In addition, in Figure 12, as shown by the dotted line γ indicating only the ridge line of one ridge 30c, as another example of an embodiment, each of the multiple ridges 30c may be configured to extend radially outward in the tire direction at an angle θb within a range inclined by 60 degrees to the other side in the tire circumferential direction, centered on a direction along the tire radial direction of the tire side surface 13 (for example, a direction along the dotted line La in Figure 12).

[0066] Fig. 13 is a view of a portion of the tire circumferential direction of the plurality of ridges 30d on the tire side surface 13 in another example of the embodiment, as viewed from the tire axially outer side. In the configuration of this example, in the configuration shown in Fig. 12, each of the plurality of ridges 30d extends along a curved shape that is curved so as to incline toward one tire circumferential side (the right side in Fig. 13) toward the tire radially outer side. Furthermore, the ridge line of each ridge 30 extends radially outward in the tire direction within a range inclined by 60 degrees toward one tire circumferential side with the tire radial direction as the center. The angle at which the ridge line of the ridge 30d inclines toward one tire circumferential side with the tire radial direction as the center gradually increases from the tire radially inner end to the tire radially outer end of the ridge 30sd. As a result, the angle θ2 at which the ridge line of the ridge 30d at the tire radial outer end thereof inclines toward one side in the tire circumferential direction from the tire radial direction as a center is greater than the angle θ1 at which the ridge line of the ridge 30d at the tire radial inner end thereof inclines toward one side in the tire circumferential direction from the tire radial direction as a center. As in the configuration of this example, each ridge 30d may be configured to extend along a curved line. In this example, the other configurations and functions are the same as those of the configurations shown in Figures 1 to 5 and 10, or the configuration shown in Figure 12.

[0067] In the above-described embodiments, the cross-sectional shape of the ridge is described as a triangle, but the ridge is not limited to this shape in the present invention. Figures 14 and 15 show two examples of ridges 30e and 30f in a pneumatic tire according to another embodiment.

[0068] 14 shows another example of ridge 30e, whose cross-sectional shape is a trapezoid having inclined sides 32 on both lateral sides. In this example, the ridge interval height ratio L / H, which is the ratio of the distance L between the centers Ld of the peaks 33 of adjacent ridges 30e to the height H of the ridges 30e, is 2 or more and 6 or less.

[0069] 15 shows another example of a ridge 30f, whose cross-sectional shape is a mountain shape with inclined sides 34 on both lateral sides and a shape that has an arcuate portion at the upper end and is connected to an outwardly convex curved portion 35. In this example, the ridge interval height ratio L / H, which is the ratio of the distance L between the centers Le of the tops of adjacent ridges 30f to the height H of the ridge 30, is 2 or more and 6 or less.

[0070] 1 to 5, the ridges 30e, 30f in each of the above examples have a cross-sectional shape along the height direction of the ridges 30e, 30f with inclined sides 32, 34 whose lateral lengths decrease toward the tips. This allows the inner surface of the groove to have a tapered surface whose width decreases toward the back when the ridges 30e, 30f are formed by groove processing in a mold used for tire molding. This makes it easier to form the groove in the mold using machining with a cutting tool or laser processing.

[0071] In the above embodiments, the ridge is formed only on the tire side surface 13 facing outward from the vehicle, but the tire mounting direction may be unspecified by forming ridges on both sides of the tire side surface. In addition, in the above embodiments, the ridge protrudes from the bottom surface of the annular recess, but the present invention is not limited to this. For example, the tire may have a configuration in which multiple ridges are regularly arranged in the tire circumferential direction protrude from the sidewall reference plane of the tire side surface. In this case, the height of the ridge may be, for example, 0.1 mm or more and 0.5 mm or less.

[0072] In addition, in the above-described embodiments, the tire side surface is provided with an annular portion 100 in which multiple ridges are arranged in a line around the entire circumference in the tire circumferential direction. However, in the above-described embodiments, instead of the annular portion 100, the tire side surface may be provided with an arc-shaped portion in which multiple ridges are arranged in a regular line around the tire circumferential direction, the arc-shaped portion being arranged in only a portion of the tire circumferential direction or in multiple separate positions around the tire circumferential direction. The arc-shaped portion may be formed by multiple ridges protruding from the bottom surface of an arc-shaped recess along the tire circumferential direction, or by multiple ridges protruding from an arc-shaped region of the sidewall reference plane along the tire circumferential direction. The arc-shaped portion and the arc-shaped region are preferably formed in a band-like range extending in the tire circumferential direction that is 25% or more of the entire circumference in the tire circumferential direction.

[0073] 10, an arcuate protrusion may be formed to form an arcuate recess with a plurality of ridges protruding therefrom, and a plurality of recesses may be formed in the arcuate protrusion to form a plurality of ridges. Also, the molding surface of the mold may be formed with an annular portion having a plurality of ridges protruding from the sidewall reference plane, or a plurality of recesses to form a plurality of ridges in an arcuate region.

[0074] The present disclosure is further illustrated by the following embodiments. Configuration 1: The tire has a plurality of ridges, which are streak-like protrusions, arranged regularly around the tire circumferential direction and formed on the tire side surface, which is the tire axially outer surface, on the tire radially inward side of the tread contact edge and on the tire radially outward side of the rim line. Each of the plurality of ridges extends radially outward in the tire circumferential direction within a range inclined by 60 degrees on both sides of the tire circumferential direction, centered on a direction along the tire radial direction of the tire side surface, and a ratio L / H of a center-to-center distance L between the apexes of adjacent ridges to a height H of the ridge is 2 or more and 6 or less. Pneumatic tires. Configuration 2: A roughness pitch ratio (Lm / Rzjis), which is the ratio of the average length Lm of elements in the roughness curve of the surface of the ridge to the ten-point average roughness Rzjis, which is the height of the irregularities, is 2 or more and 6 or less. 10. The pneumatic tire according to claim 1. Configuration 3: The arithmetic mean roughness of the surface of the ridge is 1.3 μm or more and 1.9 μm or less. 3. The pneumatic tire according to claim 1 or 2. Configuration 4: The height H of the ridge is 0.1 mm or more and 1.1 mm or less, and the width W of the ridge in a direction perpendicular to the extension direction of the ridge is 1.5 times or more and 3.5 times or less the height H of the ridge. 4. The pneumatic tire according to any one of claims 1 to 3. Configuration 5: When the center of the height H of the ridge is defined as a boundary, with the upper side being a mountain side portion and the lower side being a valley side portion, the arithmetic mean roughness of the surface of the valley side portion is smaller than the arithmetic mean roughness of the surface of the mountain side portion. 5. The pneumatic tire of any one of configurations 1 to 4. Configuration 6: The plurality of ridges are formed on the tire side surface so as to protrude from the bottom surface of a recess recessed from the sidewall reference plane toward the tire inner surface. 6. The pneumatic tire of any one of configurations 1 to 5. Configuration 7: The plurality of ridges are formed on the tire side surface within a tire radial range of 5% to 65% when the tire radial position of the rim line is set to 0 and the tire cross-sectional height is set to 100. 7. The pneumatic tire of any one of claims 1 to 6. Configuration 8: A mold for molding a pneumatic tire for molding the pneumatic tire according to any one of Configurations 1 to 7, A mold for molding a pneumatic tire has a molding surface having a plurality of recesses corresponding to the plurality of ridges. [Explanation of symbols]

[0075] 1 pneumatic tire (tire), 10 tread, 12 sidewall, 13 tire side surface, 14 sidewall reference surface, 18 rim strip, 19 rim protector, 20 rim line, 30, 30a, 30b, 30c, 30d, 30e, 30f ridge, 31 ridge line, 32 inclined edge, 33 top portion, 34 inclined edge, 35 curved portion, 37 annular recess, 38 bottom surface, 39 open end, 40 wake region, 70 tire molding mold, 71 tread mold, 72 side mold, 73 tread molding surface, 74 main body, 75 protrusion, 76 main body, 77a, 77b side molding surface, 78 annular protrusion, 78a top surface, 80 recess, 81 mountain side portion, 82 valley side portion, 100 annular portion, T ground contact edge.

Claims

1. The tire has a plurality of ridges, which are streak-like protrusions, arranged regularly in the tire circumferential direction and formed on the tire side surface, which is the tire axially outer surface, on the tire radially inner side of the ground contact edge of the tread and on the tire radially outer side of the rim line. Each of the plurality of ridges extends radially outward in the tire circumferential direction within a range inclined by 60 degrees on both sides of the tire circumferential direction, centered on a direction along the tire radial direction of the tire side surface, and a ratio L / H of a center-to-center distance L between apexes of adjacent ridges to a height H of the ridge is 2 or greater and 6 or less. Pneumatic tires.

2. a roughness pitch ratio (Lm / Rzjis) which is the ratio of the average length Lm of elements in the roughness curve of the surface of the ridge to the ten-point average roughness Rzjis which is the height of the irregularities, is 2 or more and 6 or less; The pneumatic tire according to claim 1 .

3. the arithmetic mean roughness of the surface of the ridge is 1.3 μm or more and 1.9 μm or less; The pneumatic tire according to claim 1 .

4. a height H of the ridge is 0.1 mm or more and 1.1 mm or less, and a width W of the ridge in a direction perpendicular to the extension direction of the ridge is 1.5 times or more and 3.5 times or less the height H of the ridge; The pneumatic tire according to claim 1 .

5. When the center of the ridge in the height H direction is defined as a boundary, the upper side is a mountain side portion and the lower side is a valley side portion, the arithmetic mean roughness of the surface of the valley side portion is smaller than the arithmetic mean roughness of the surface of the mountain side portion. The pneumatic tire according to claim 1 .

6. the plurality of ridges are formed on the tire side surface so as to protrude from a bottom surface of a recessed portion recessed from a sidewall reference plane toward the tire inner surface, The pneumatic tire according to claim 1 .

7. The plurality of ridges are formed on the tire side surface within a range in the tire radial direction of 5% to 65% when the tire radial direction position of the rim line is set to 0 and the tire cross-sectional height is set to 100. The pneumatic tire according to claim 1 .

8. A pneumatic tire mold for molding the pneumatic tire according to any one of claims 1 to 7, A mold for molding a pneumatic tire has a molding surface having a plurality of recesses corresponding to the plurality of ridges.

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