Pneumatic Tire and Mold for Molding Pneumatic Tire

Abstract

In a configuration having a plurality of ridges arranged in the tire circumferential direction on the tire side surface, an inflated tire capable of reducing air resistance is provided. 【Solution means】A tire which is an example of an embodiment includes ridges 30 which are a plurality of ridge-like protrusions formed on a tire side surface which is on the inner side in the tire radial direction from the ground contact end of the tread and on the outer side in the tire radial direction from the rim line and on the outer surface in the tire axial direction. Each ridge extends radially outward of the tire within a range inclined 60 degrees to both sides in the tire circumferential direction about the direction along the tire radial direction of the tire side surface 13. The ratio L / H of the center-to-center distance L between the tops of adjacent ridges 30 and the height H of the ridge is 2 or more and 6 or less.

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 provided with ridges which are a plurality of rib-like protrusions formed on a tire side surface which is an outer surface in the tire axial direction on the outer side in the tire radial direction from the rim line.

Background Art

[0002] In recent years, in order to improve the design of tires and the visibility of displays on the tire side portion, it has been considered to provide a plurality of ridges which are rib-like protrusions on the tire side portion. For example, Patent Document 1 describes a configuration in which a plurality of ridges are arranged in a predetermined region of the sidewall portion of a tire in order to improve the visibility and cleaning performance of the tire side portion. In this configuration, the plurality of ridges are parallel to each other and periodically protrude from the base surface, and the range of the length Lb of one period of the plurality of ridges along the base surface is regulated in relation to the length Lr of one period along the contour of the ridge in a cross-sectional view of the ridge. Further, in Patent Document 1, it is said that the hydrophilicity at the ridge can be enhanced by setting the arithmetic mean roughness of the rubber on the ridge surface to 0.1 μm or more and 5 μm or less.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, with the improvement of the design of tires, it has been desired to reduce the air resistance in tires. When a plurality of ridges are provided on the tire side portion as in the configuration described in Patent Document 1, there is a possibility of improving the design of the tire. However, simply regulating the length of one cycle of the ridge in relation to the length along the contour of the ridge or regulating the surface roughness of the ridge as in the configuration described in Patent Document 1 cannot achieve the effect of reducing air resistance by suppressing air separation. For this reason, in a configuration having a plurality of ridges arranged in the tire circumferential direction on the tire side surface, there is room for improvement in terms of realizing a tire capable of reducing air resistance.

[0005] An object of the present invention is to provide a pneumatic tire capable of reducing air resistance and a mold for molding the same in a configuration having a plurality of ridges arranged in the tire circumferential direction on the tire side surface.

Means for Solving the Problems

[0006] The pneumatic tire according to the present invention is formed on the tire side surface, which is the outer surface in the tire axial direction on the inner side in the tire radial direction from the ground contact end of the tread and on the outer side in the tire radial direction from the rim line, and includes ridges that are a plurality of rib-like protrusions regularly arranged in the tire circumferential direction. Each of the plurality of ridges extends radially outward of the tire within a range inclined 60 degrees to both sides in the tire circumferential direction around the direction along the tire radial direction of the tire side surface, and the ratio L / H of the center-to-center distance L between the tops of adjacent ridges to the height H of the ridge is 2 or more and 6 or less. It is a pneumatic tire.

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

Effects of the Invention

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

Brief Description of the Drawings

[0009]

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Mode for Carrying Out the Invention

[0010] Hereinafter, with reference to the drawings, 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. The embodiments described below are merely examples, and the present invention is not limited to the following embodiments. Also, selectively combining the components of the plurality of embodiments and modification examples described below is included in the present invention.

[0011] FIG. 1 is a view showing a tire contour shape in a meridian cross-section of a pneumatic tire 1 which is an example of the embodiment, and is a view showing a formation range of a plurality of ridges. As shown in FIG. 1, the pneumatic tire 1 includes a tread 10 which is a portion in 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 a plurality of blocks and is formed annularly along the tire circumferential direction. In the illustrated example, the tread 10 is shown as being formed of a single block, but actually, the tread 10 includes a plurality of blocks divided in the tire axial direction X. The plurality of blocks are divided by circumferential grooves extending in the tire circumferential direction. The tread 10 has a ground contact end T. In FIG. 1, the tire axial direction is indicated by X, and the tire radial direction is indicated by Y.

[0012] Hereinafter, as the structure of the tire 1, the part on the outer side (OUT side) of the vehicle centered on the tire axial center CL in the tire axial direction X will be described. The tire 1 is symmetric between the outer part and the inner part of the vehicle of the tire 1 with respect to the shape other than the annular part 100 provided with the ridge on the tire side surface described later.

[0013] The tire 1 includes a sidewall 12 provided at the end on the outer side in the tire axial direction X from the tread 10 and bulging most on the outer side in the tire axial direction X, and a bead (not shown) fixed to the rim of the wheel. The sidewall 12 and the bead are formed annularly 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. At the inner end in the radial direction Y of the tire 1, a rim strip 18 forming the outer surface of the bead is provided adjacent to the sidewall 12.

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

[0015] In this specification, unless otherwise specified, the dimensions of each part of the tire are the dimensions measured in the unloaded normal state in which the unused tire is mounted on the normal rim and filled with air so as to reach the normal internal pressure.

[0016] The "ground contact end T" means both ends in the tire axial direction X of the region that contacts the flat road surface when a load of 88% of the normal load at the normal internal pressure is applied in a state where the unused tire 1 is mounted on the normal rim and filled with air so as to reach the normal internal pressure.

[0017] Here, the "regular rim" refers to the rim defined by the tire standard, which is the "standard rim" in JATMA, the "Design Rim" in TRA, and the "Measuring Rim" in ETRTO. The "regular internal pressure" is the "maximum air pressure" in JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, and the "INFLATION PRESSURE" in ETRTO. The "regular load" is the "maximum load capacity" in JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, and the "LOAD CAPACITY" in ETRTO.

[0018] Tire 1 includes a carcass, a belt layer, and an inner liner. The carcass is a cord layer covered with rubber and forms the skeleton of Tire 1 that withstands loads, impacts, air pressure, etc. The belt layer is a reinforcing belt disposed between the tread rubber 11 and the carcass. The belt layer tightly compresses the carcass to increase the rigidity of Tire 1. The belt layer is formed by a plurality of belts overlapping in the tire radial direction Y. Each belt is formed by covering a plurality of cords arranged in a direction inclined with respect to the tire circumferential direction with rubber. In adjacent belts, the cords are inclined in opposite directions with respect to the tire circumferential direction so that the cords of each other cross. The cords are formed of steel or the like.

[0019] A belt reinforcing layer that extends in the tire circumferential direction and covers the entire tire axial direction X of the belt layer is provided between the belt layer and the tread rubber. The belt reinforcing layer is formed by covering a cord that extends substantially in the tire circumferential direction with rubber. The cord is formed of organic fiber or the like.

[0020] For Tire 1 of the embodiment, the mounting direction of the front and back of Tire 1 with respect to the vehicle is specified. That is, the outer and inner sides of Tire 1 with respect to the vehicle are specified respectively. In FIG. 1, Tire 1 is mounted on the vehicle such 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] On the tire sidewall, there is generally a symbol called a serial number. The serial number includes information such as size code, manufacturing date (manufacturing year and week), manufacturing location (manufacturing plant code), etc. By providing the serial number only on the tire sidewall (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, the mounting direction of the tire 1 with respect to the vehicle is specified. As a specific example, a manufacturing plant code and a size code are provided on both side surfaces of the tire 1, and the manufacturing year and week are provided only on the side surface facing the outside in the width direction of the vehicle.

[0022] Also, on the tire sidewall facing the outside of the vehicle, there may be provided a display indicating that it is the outside in the mounted state on the vehicle, in the form of characters or symbols.

[0023] Also, as a part of the rim strip rubber forming the rim strip 18, a rim protector 19 protruding outward in the tire axial direction is provided. The rim line 20 is provided annularly along the tire circumferential direction at the apex located at the outer end in the tire axial direction of the rim protector 19. The rim protector 19 has a function of protecting the rim from trauma. The rim line 20 is a line for confirming that the tire 1 is mounted on the rim at an appropriate position, by means of the gap with the rim. In FIG. 1, the rim protector 19 is provided, but as shown by the two-dot chain line in FIG. 1, a configuration without the rim protector 19 may also be used. Even in this case, a rim line, which is an annularly formed protrusion protruding outward in the tire axial direction, is provided on the tire sidewall for confirming that the tire 1 is mounted on the rim at an appropriate position.

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

[0025] FIG. 2 is a view of a part of the tire 1 of the embodiment as seen from the outside in the tire axial direction in the tire circumferential direction. As shown in FIG. 2, an annular portion 100 having a constant tire radial length over the entire circumference in the tire circumferential direction is provided on the tire side surface 13 facing the outside of the vehicle. The annular portion 100 is formed by a plurality of ridge-shaped protrusions, ridges 30, arranged at equal intervals in the tire circumferential direction protruding outward in the tire axial direction from the annular recess 37. Each ridge 30 extends in the tire radial direction. Also, each ridge 30 has the same shape as the others. As will be described later, the tire of the present invention may be configured to include an arc-shaped portion and an arc-shaped recess provided at a part or a plurality of positions in the tire circumferential direction of the tire side surface, with a plurality of ridges arranged side by side in the tire circumferential direction, instead of the annular portion 100 and the annular recess 37.

[0026] FIG. 3 is a perspective view showing a partial cutaway of the annular portion 100, which is the ridge 30 forming portion, in the embodiment. The plurality of ridges 30 are arranged in an annular recess 37 provided along the tire circumferential direction on the tire side surface 13. The annular recess 37 is recessed over the entire circumference in the tire circumferential direction with substantially the same depth and the same tire radial width from the sidewall reference plane 14 (FIGS. 2 and 3) toward the inner surface side of the tire.

[0027] The sidewall reference plane 14 means the surface of the sidewall 5 facing the outside in the tire axial direction at a portion of the tire side surface 13 where no partial unevenness such as protrusions or recesses like side blocks is formed.

[0028] The plurality of ridges 30 project outward in the tire axial direction from the bottom surface 38 of the annular recess 37 and are arranged at equal intervals in the tire circumferential direction. The bottom surface 38 is a protrusion formation reference plane and is a part of the tire side surface 13. In a cross-sectional view of the portion where each ridge 30 rises on the bottom surface 38, it can be a straight line. "Arranged at equal intervals" means that the intervals between adjacent ridges 30 at the same tire radial position are uniform among the plurality of ridges 30. Thereby, the plurality of ridges 30 are regularly arranged in the tire circumferential direction.

[0029] Each ridge 30 has a triangular cross-sectional shape orthogonal to the extending direction and is continuous in the tire diameter direction, which is the extending direction, with substantially the same cross-sectional shape. As a result, each ridge 30 extends radially outward of the tire within a range inclined 60 degrees to both sides in the tire circumferential direction about the direction along the tire diameter direction of the tire side surface 13.

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

[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 larger 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] As shown in FIG. 4, the height H of the ridge 30 is, for example, 0.3 mm or more and 1.1 mm or less. On the other hand, 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 by 0.1 mm or more from the opening end 39 of the annular recess 37. In this way, since a part of the ridge 30 protrudes outward from the opening end 39 of the annular recess 37, the presence of the ridge 30 can be emphasized 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 the direction orthogonal to the extending direction of the ridge 30, is 1.5 or more and 3.5 or less of the height H of the ridge 30.

[0034] In addition, the ridge interval height ratio L / H, which is the ratio of the distance L between the centers of the tops of adjacent ridges 30 (ridge line 31 interval) to the height H of the ridge 30, is 2 or more and 6 or less. In the case of this example, since each ridge 30 extends in the tire diameter direction, the ridge line distance L widens from the inner side to the outer side in the tire diameter direction. Even in this case, throughout the entire extending direction of the ridge 30, the ridge interval height ratio L / H is 2 or more and 6 or less. Thereby, while reducing the air resistance of the tire 1, it is possible to suppress a decrease in appearance.

[0035] FIG. 5 is a schematic diagram showing that, in the embodiment, after the air flow indicated by the arrow α collides with the ridge 30 on the bottom surface 38, reattachment of the air flow to another ridge 30 on the downstream side occurs due to turbulent flow, and the separation point tends to be on the downstream side. In the embodiment, since the above-described ridge interval height ratio L / H is 2 or more and 6 or less, the air flow that collides with the ridge 30 on the bottom surface 38 becomes turbulent flow and heads downstream, and the turbulent flow collides again with another ridge 30 on the downstream side and is repeated. As a result, the separation point of the air flow on the tire side surface 13 tends to shift to the downstream side. For this reason, as will be described later, in the air flow downstream side of the tire, the width of the wake region that is formed by the portion sandwiched from both sides by the separated air flow from the separation position of the tire side surface 13 and becomes a negative pressure can be reduced. For this reason, since the pressure resistance due to the formation of the ridge 30 can be reduced, an increase in air resistance can be suppressed.

[0036] FIG. 6 is a schematic diagram showing that, in a comparative example where the ridge interval height ratio L / H is less than 2, the surface of the tire side surface including the ridge 30a does not generate turbulent flow in the same manner as a smooth surface. When the above-described ridge interval height ratio L / H is less than 2, as shown in FIG. 6, the density of the plurality of ridges 30a per unit area of the tire side surface increases. As a result, the tire side surface becomes similar to a smooth surface in relation to the air flow indicated by the arrow α, so it becomes difficult to generate turbulent flow in the air flow. For this reason, the effect of shifting the separation point of the air flow on the tire side surface to the downstream side hardly occurs. Therefore, since the negative pressure reduction effect becomes low, the air resistance increase suppression effect becomes small.

[0037] On the other hand, when the ridge interval height ratio L / H exceeds 6, the formation amount of the ridge 30 on the tire side surface 13 decreases, so the negative pressure reduction effect decreases. Also in this case, the effect of suppressing the increase in air resistance becomes small.

[0038] Using FIGS. 7 and 8, the effects of the embodiment will be described in more detail. FIG. 7 is a schematic diagram showing a simulation using a cylinder Sa of the occurrence of a wake region 40 due to a separated air flow on the downstream side of the air flow from the tire side surface 13 in a comparative example where the ridge interval height ratio is less than 2. In FIG. 7, many turbulent flows are formed inside the wake region 40. In FIGS. 7 and 8, the tire is shown by simulation using a cylinder Sa.

[0039] In the comparative example shown in FIG. 7, since the above-mentioned ridge interval height ratio is less than 2, the tire side surface 13 does not generate turbulent flow like a smooth surface as described above. In this case, considering that the air flow indicated by the broken line collides with the surface of the cylinder Sa as the tire side surface 13 as the tire rotates during vehicle travel. In this case, a positive pressure is generated on the upstream side of the air flow of the cylinder Sa so as to press the cylinder Sa downstream. Then, when flowing from the upstream side of the air flow of the cylinder Sa along the surface of the cylinder Sa to the downstream side, the air flow separates from the surface of the cylinder Sa at positions C1 and C2 in FIG. 13. And, a wake region 40 with a negative pressure is formed by the portion sandwiched from both sides by the separated air flow from the separation position of the cylinder Sa. In the case of FIG. 7, since the width of this wake region 40 (the vertical length in FIG. 7) becomes large, the negative pressure reduction effect is small. From this, when the ridge interval height ratio is less than 2, the effect of suppressing the increase in pressure resistance in the tire is low, so the effect of suppressing the increase in air resistance becomes small.

[0040] FIG. 8 is a schematic diagram showing a simulation using a cylinder S in the embodiment that the width of the wake region 40 due to the separated air flow on the downstream side of the air flow from the tire side surface 13 becomes narrow and the negative pressure reduction effect becomes high. In FIG. 8, the formation of a plurality of ridges 30 on the tire side surfaces 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 the embodiment, since the above-mentioned ridge interval height ratio is 2 or more and 6 or less, for the reasons described with reference to FIG. 5, the separation points of the air flow from the tire side surface 13 tend to shift to positions C3 and C4 on the downstream side. As a result, on the downstream side of the cylindrical body S simulating the tire, the width of the wake region 40, which is formed in the portion sandwiched from both sides by the separated air flow from the separation position on the surface of the cylindrical body S and becomes a negative pressure, can be reduced. FIG. 8 simulates that a plurality of ridges 30 are formed on the tire side surfaces 13 on both sides in the tire axial direction. However, even when a plurality of ridges 30 are formed only on the tire side surface 13 on the outer side of the vehicle as in the embodiment, the width of the wake region 40 is reduced. From this, in the embodiment, since the effect of suppressing the increase in pressure resistance in the tire is enhanced, an increase in air resistance can be suppressed.

[0042] Furthermore, in the embodiment, minute irregularities are formed on the surface of each ridge 30, and due to the irregularities, the surface of the ridge 30 has an appropriate surface roughness. As a result, it becomes easier to form an appropriate turbulent boundary layer in the vicinity of the surface of the ridge 30 on the tire side surface for the air flow. Thereby, the position where the air flow separates from the ridge 30 can be shifted more downstream. For this reason, since the width of the wake region formed on the downstream side of the ridge 30 and where the speed of the air flow becomes small can be reduced, an increase in the air resistance of the tire 1 can be further suppressed.

[0043] Specifically, the roughness pitch ratio, which is the ratio (Lm / Rzjis) of the average length Lm of the elements in the roughness curve of the surface of the ridge 30 to the ten-point average roughness Rzjis, which is the unevenness height, is 2 or more and 6 or less. FIG. 9 shows a method for obtaining the average length Lm of the elements in the surface roughness curve of the ridge 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 having a certain length extracted from the roughness curve for obtaining roughness parameters such as the ten-point average roughness.

[0044] Specifically, as shown in FIG. 9, in the surface roughness curve of the ridge 30, a reference length Lx (arbitrarily set within the range of 0.5 mm to 5 mm) along the direction of the average line LG of the uneven height is extracted and considered. In this case, with the average line LG of the extracted portion as a reference, the peak portion that exceeds the average line LG upward and the valley portion that goes below the average line LG and becomes lower are regarded as one element of one cycle where they are continuous one by one. Then, the value obtained by dividing the sum of the lengths L1, L2 ··· LN along the average line of the elements from the first cycle to the Nth cycle at the reference length Lx by the number of cycles N is determined as the average length Lm of the elements. That is, Lm = (L1 + L2 + L3 + ··· + LN) / N.

[0045] The measurement method of the ten-point mean roughness Rzjis conforms to JIS B 0601:2001 based on ISO4287 - 1987. Specifically, when obtaining the ten-point mean roughness Rzjis, in the above-mentioned extracted portion, the absolute value of the average value of the heights from the average line LG of five peaks from the peak with the highest height from the average line LG to the fifth highest peak is obtained. Also, in the above-mentioned extracted portion, the absolute value of the average value of the depths from the average line LG of five valleys from the valley with the lowest depth from the average line LG to the fifth lowest valley is obtained. The sum of the absolute value of the average value of these heights and the absolute value of the average value of these depths is the ten-point mean roughness Rzjis. In the case of this example, the roughness pitch ratio, which is the ratio (Lm / Rzjis) of the average length Lm of the elements to the ten-point mean roughness Rzjis, which is the uneven height, is 2 or more and 6 or less. Thereby, the width of the wake region formed on the downstream side of the ridge 30 where the velocity of the air flow becomes small can be reduced, so that the increase in the air resistance of the tire 1 can be further suppressed.

[0046] Also, in the embodiment, the plurality of ridges 30 may be formed within a tire radial Y range of 5% or more and 65% or less (within the range indicated by the arrow β in FIG. 1) on the tire side surface 13 with the tire radial position of the rim line 20 being 0 and the tire section height Ht being 100.

[0047] According to this configuration, the ridge 30 can be provided in the range of the outer peripheral portion of the tire, which is highly conspicuous and has a high effect of improving the design, from the vicinity of the outer end in the tire axial direction (P in FIG. 1) corresponding to the maximum width of the tire on the tire side surface 13 to the outer portion in the tire radial direction Y where the air flow is likely to hit.

[0048] Further, in the ridge 30 of this example, the cross-sectional shape along the height direction is a triangular shape having an inclined side whose lateral length decreases toward the tip. Thereby, when the ridge 30 is formed by grooving the mold used at the time of tire molding, the inner surface of the groove can be a tapered surface whose width decreases toward the back. For this reason, it becomes easy to form a groove in the mold by using machining with a cutting tool or laser processing.

[0049] FIG. 10 is a cross-sectional view showing a tire molding die of the embodiment. The tire 1 of this embodiment is formed by a tire molding die 70. Hereinafter, the tire molding die 70 is referred to as the die 70. The die 70 is a die for molding the tire 1 shown in FIGS. 1 to 5 described above. According to the die 70, a tire 1 having a plurality of ridges 30 arranged in the tire circumferential direction on the tire side surface 13 and capable of reducing air resistance can be realized.

[0050] Hereinafter, each member will be described according to the tire axial direction X and the tire radial direction Y of the above-described tire 1 molded by the die 70.

[0051] The die 70 has a tread die 71 for molding the surface of the tread of the tire 1 and a pair of side dies 72 for molding the surface of the sidewall.

[0052] The tread die 71 has a main 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 metallic material, for example, an aluminum alloy. As the aluminum alloy, for example, the AC4 series, AC7 series, etc. are preferably used. The protrusion 75 is a portion for forming a circumferential groove in the tire 1. The protrusion 75 is made of the same material as the metallic material constituting the main body 74.

[0054] The side mold 72 has a main body 76 having side forming surfaces 77a and 77b. The side forming surface 77a for forming the tire side surface on the outer side of the vehicle has an annular protrusion 78 protruding outward from the side forming surface 77a. The main body 76 is made of the same metallic material as the main body 74. The annular protrusion 78 is a portion for forming, in the tire 1, an annular recess 37 (FIGS. 3 and 4) in which a plurality of ridges 30 bulge from the bottom surface 38.

[0055] The tread mold 71 is in a fan shape in plan view formed by dividing an annular body into a plurality of parts in the circumferential direction. The plurality of divided tread molds 71 form a continuous body in an annular shape so as to have an inner diameter corresponding to the outer diameter of the tire 1 to be molded in the mold clamping state described later. The upper side mold 72 is annular and is fixed to the lower surface of an upper plate (not shown) constituting the vulcanizing molding machine, and moves up and down as the first elevating member (not shown) moves up and down. The lower side mold 72 is annular and is fixed to the floor surface and is fixed to the lower surface of a lower plate (not shown) constituting the vulcanizing molding machine. The vulcanizing molding machine moves up and down a plurality of segments (not shown) provided one by one for each one tread mold 71 outside the plurality of divided tread molds 71 by the first elevating member. Simultaneously with the up and down movement of the first elevating member, the vulcanizing molding machine slides the inclined surfaces of the outer peripheral surfaces of the plurality of segments in the vertical direction on an inclined cylindrical surface provided at the lower end of a second elevating member (not shown) that moves up and down independently of the first elevating member. Thereby, the vulcanizing molding machine reciprocates the plurality of segments in the radial direction with respect to the central axis of the annularly continuous tread mold 71. Thereby, the vulcanizing molding machine switches the mold 70 between the mold clamping state and the mold opening state.

[0056] In the mold 70 configured as described above, with the tire axial direction along the vertical direction in the mold open state, the green tire is placed on the lower tread mold 71. Then, an inflatable bladder is disposed inside the green tire, and the bladder is inflated by supplying air to the bladder. Then, with the inner surface of the green tire held by the outer surface of the bladder, the first elevating member and the second elevating member are raised and lowered to clamp the mold 70. The rubber of the green tire adheres to the tread forming surface 73 and the side forming surfaces 77a and 77b due to the pressing force from the mold 70, and a heat exchange medium adjusted to a predetermined temperature is constantly circulated through the members fixing the upper plate and the members fixing the lower plate. Thereby, the rubber of the green tire is vulcanized, and the tire 1 having a predetermined shape is completed.

[0057] In the present embodiment, in the side forming surface 77a for forming the tire side surface 13 on the outer side of the vehicle, an annular protrusion 78 for forming an annular recess 37 in which a plurality of ridges 30 bulge is formed. The top surface 78a of the annular protrusion 78 corresponds to the bottom surface 38 of the annular recess 37. Further, a plurality of recesses 80 corresponding to the plurality of ridges 30 provided on the tire side surface 13 are formed at a plurality of positions in the circumferential direction of the annular protrusion 78. The recess 80 is recessed in a groove shape extending in a substantially triangular cross section from the top surface 78a.

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

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

[0060] FIG. 11 is a view showing a mountain - side portion 81 and a valley - side portion 82 having different arithmetic mean surface roughnesses using the cross - sectional shape of the ridge 30a in a tire according to another example of the embodiment. As shown in FIG. 11, in the configuration of this example, the surface roughnesses of the mountain - side portion 81 and the valley - side portion 82 in each ridge 30a are different. Specifically, when the center C in the height H direction of the ridge 30a is taken as a boundary, with the upper side being the mountain - side portion 81 and the lower side being the valley - side portion 82, the arithmetic mean surface roughness of the valley - side portions 82 on both sides in the width direction is smaller than the arithmetic mean surface roughness of the mountain - side portions 81 on both sides in the width direction. Even in this case, it is preferable that the arithmetic mean surface roughness of each of the surfaces of the mountain - side portion 81 and the valley - side portion 82 of the ridge 30a is 1.3 μm or more and 1.9 μm or less.

[0061] According to the configuration of this example, the arithmetic mean surface roughness of the valley - side portion 82 is smaller than that of the mountain - side portion 81. Thus, when the ridge 30a is arranged obliquely or along the horizontal direction with respect to the vertical direction in response to the rotation of the tire during vehicle travel, the air resistance of the air passing through the inside of the valley - side portion 82, which is the side where the air resistance is likely to increase among the mountain - side portion 81 and the valley - side portion 82, can be reduced. Thereby, the air resistance in the tire can be further reduced. In this example, other configurations and operations are the same as those shown in FIGS. 1 - 5 and FIG. 10.

[0062] FIG. 12 is a view of a part of the tire circumferential direction of a plurality of ridges 30b on the tire side surface 13 in another example of the embodiment, as viewed from the outside in the tire axial direction, with the tire circumferential direction extended horizontally. In the configuration of this example, the plurality of ridges 30b provided in the annular recess 37 on the tire side surface 13 are inclined toward one side (the right side in FIG. 12) in the tire circumferential direction with respect to the tire radial direction, toward the outside in the tire radial direction. In FIG. 12, only the ridge lines of each ridge 30b are shown for each ridge 30b.

[0063] And a plurality of ridges 30b project outward in the tire axial direction from the bottom surface 38 of the annular recess 37 and are arranged at equal intervals in the tire circumferential direction. Also in this example, "arranged at equal intervals" means that the intervals between adjacent ridges 30b at the same tire radial position are uniform among the plurality of ridges 30b.

[0064] Furthermore, each ridge 30b extends outward in the tire radial direction at an angle θa within a range of 60 degrees inclined toward one side in the tire circumferential direction about the direction along the tire radial direction of the tire side surface 13 (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 toward one side in the tire circumferential direction about the direction along the tire radial direction, but the inclination angle may be 10 degrees, 20 degrees, or 30 degrees, etc. Also in this example, the ratio L / H of the ridge line distance L between the centers of the tops of adjacent ridges 30 to the height H of the ridge 30 is 2 or more and 6 or less throughout the extending direction of the ridge 30. In this example, other configurations and operations are the same as those shown in FIGS. 1 to 5 and FIG. 10.

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

[0066] FIG. 13 is a view of a part of a plurality of ridges 30d on the tire side surface 13 in another example of the embodiment, as viewed from the outside in the tire axial direction. 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 curves so as to incline toward one side in the tire circumferential direction (the right side in FIG. 13) toward the outside in the tire radial direction. Further, the ridge lines of each ridge 30 extend outward in the tire radial direction within a range where the whole ridge line inclines 60 degrees toward one side in the tire circumferential direction around the direction along the tire radial direction. The angle at which the ridge line of the ridge 30d inclines toward one side in the tire circumferential direction around the direction along the tire radial direction gradually increases from the inner end in the tire radial direction to the outer end in the tire radial direction of the ridge 30sd. Thereby, at the outer end in the tire radial direction of the ridge 30d, the angle θ2 at which the ridge line of the ridge 30d inclines toward one side in the tire circumferential direction around the direction along the tire radial direction is larger than the angle θ1 at which the ridge line of the ridge 30d inclines toward one side in the tire circumferential direction around the direction along the tire radial direction at the inner end in the tire radial direction of the ridge 30d. Each ridge 30d may be configured to extend along the curve direction as in the configuration of this example. In this example, the other configurations and operations are the same as those shown in FIGS. 1 to 5 and FIG. 10, or the configuration shown in FIG. 12.

[0067] In each of the above embodiments, the case where the cross-sectional shape of the ridge is triangular has been described. However, in the present invention, the ridge is not limited to such a shape. FIGS. 14 and 15 show two examples of the ridges 30e and 30f in a pneumatic tire of another example of the embodiment.

[0068] First, in the ridge 30e of the other example shown in FIG. 14, the cross-sectional shape is trapezoidal with inclined sides 32 on both lateral sides. In the case of this example, the ridge interval height ratio L / H, which is the ratio of the distance L between the centers Ld of the tops 33 of adjacent ridges 30e to the height H of the ridge 30e, is 2 or more and 6 or less.

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

[0070] Also in the ridges 30e and 30f of each of the above examples, similar to the ridge 30 of the embodiment shown in Figs. 1 to 5, the cross-sectional shape along the height direction of the ridges 30e and 30f has inclined sides 32 and 34 whose lateral length becomes smaller toward the tip. Thereby, when forming the ridges 30e and 30f by grooving the mold used at the time of tire molding, the inner surface of the groove can be a tapered surface whose width becomes smaller toward the back. For this reason, it becomes easy to form a groove in the mold by using machining with a cutting tool or laser processing.

[0071] In each of the above embodiments, the ridge is formed only on the tire side surface 13 facing the outside of the vehicle. However, by forming the ridge on the tire side surfaces on both sides of the vehicle, it may be configured not to specify the mounting direction of the tire. Also, in each of the above embodiments, the case where the ridge protrudes from the bottom surface of the annular recess has been described. However, the present invention is not limited to this. For example, a configuration may be adopted in which a plurality of ridges regularly arranged in the tire circumferential direction protrude from the sidewall reference surface 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 each of the above embodiments, the case where an annular portion 100 in which a plurality of ridges are arranged along the entire circumference in the tire circumferential direction is provided on the tire side surface has been described. However, in each of the above embodiments, instead of the annular portion 100, on the tire side surface, it may be configured to include an arc-shaped portion provided only in a part of the tire circumferential direction or provided separately at a plurality of positions in the tire circumferential direction, in which a plurality of ridges are regularly arranged in the tire circumferential direction. The arc-shaped portion may be formed by a plurality of ridges protruding from the bottom surface of an arc-shaped concave portion along the tire circumferential direction, or may be formed by a plurality of ridges protruding from an arc-shaped region along the tire circumferential direction of the sidewall reference surface. The arc-shaped portion and the arc-shaped region are preferably formed in a strip-shaped range extending in the tire circumferential direction of 25% or more with respect to the entire circumference in the tire circumferential direction.

[0073] Further, instead of the annular protrusion 78 formed on the side forming surface 77a of the mold 70 shown in FIG. 10, an arc-shaped protrusion for forming an arc-shaped concave portion in which a plurality of ridges bulge may be formed, and a plurality of concave portions for forming a plurality of ridges may be formed on the arc-shaped protrusion. Further, on the forming surface of the mold, an annular portion having a plurality of ridges protruding from the sidewall reference surface or a plurality of concave portions for forming a plurality of ridges in an arc-shaped region may be formed.

[0074] The present disclosure will be further described by the following embodiments. Configuration 1: A tire side surface that is the outer surface in the tire axial direction inside the tire radial direction from the ground contact end of the tread and outside the tire radial direction from the rim line, and includes ridges that are a plurality of rib-like protrusions regularly arranged in the tire circumferential direction. Each of the plurality of ridges extends radially outward of the tire within a range inclined 60 degrees to both sides in the tire circumferential direction about the direction along the tire radial direction of the tire side surface, and the ratio L / H of the center-to-center distance L between the tops of adjacent ridges to the height H of the ridge is 2 or more and 6 or less. Pneumatic tire. Configuration 2: The roughness pitch ratio, which is the ratio (Lm / Rzjis) of the average length Lm of the elements in the roughness curve of the surface of the ridge to the ten-point average roughness Rzjis, which is the unevenness height, is 2 or more and 6 or less. The pneumatic tire according to Configuration 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. The pneumatic tire according to Configuration 1 or Configuration 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 the direction orthogonal to the extending 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 any one of Configurations 1 to 3. Configuration 5: When the upper side is the mountain side portion and the lower side is the valley side portion with the center of the height H of the ridge as the boundary, 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 any one of Configurations 1 to 4. Configuration 6: A plurality of the ridges are formed so as to protrude from the bottom surface of a recess that is recessed toward the inner surface side of the tire from the sidewall reference surface on the tire side surface. The pneumatic tire according to any one of Configurations 1 to 5. Configuration 7: A plurality of the ridges are formed within a tire radial range of 5% or more and 65% or less when the tire radial position of the rim line is 0 and the tire section height is 100 on the tire side surface. The pneumatic tire according to any one of Configurations 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 having a plurality of recesses corresponding to the plurality of ridges on the molding surface.

Explanation of Reference Numerals

[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 side, 33 Top, 34 Inclined side, 35 Curved portion, 37 Annular recess, 38 Bottom surface, 39 Open end, 40 Rear flow region, 70 Mold for tire molding, 71 Tread mold, 72 Side mold, 73 Tread molding surface, 74 Main body, 75 Projection, 76 Main body, 77a, 77b Side molding surface, 78 Annular protrusion, 78a Top surface, 80 Recess, 81 Crest side portion, 82 Trough side portion, 100 Annular portion, T Ground contact end.

Claims

1. A tire side surface which is on the inner side in the tire radial direction from the ground contact end of the tread and on the outer side in the tire radial direction from the rim line, and is formed on the outer side surface in the tire axial direction, and includes ridges which are a plurality of rib-like protrusions regularly arranged in the tire circumferential direction. Each of the plurality of ridges extends outward in the tire radial direction within a range inclined 60 degrees on both sides in the tire circumferential direction with respect to the direction along the tire radial direction of the tire side surface, and the ratio L / H of the center-to-center distance L between the tops of adjacent ridges to the height H of the ridge is 2 or more and 6 or less. The roughness pitch ratio, which is the ratio (Lm / Rz jis) of the average length Lm of the elements in the roughness curve of the surface of the ridge to the ten-point average roughness Rz jis which is the unevenness height, is 2 or more and 6 or less. And the arithmetic mean roughness of the surface of the ridge is 1.3 μm or more and 1.9 μm or less. A pneumatic tire.

2. A tire side surface which is on the inner side in the tire radial direction from the ground contact end of the tread and on the outer side in the tire radial direction from the rim line, and is formed on the outer side surface in the tire axial direction, and includes ridges which are a plurality of rib-like protrusions regularly arranged in the tire circumferential direction. Each of the plurality of ridges extends outward in the tire radial direction within a range inclined 60 degrees on both sides in the tire circumferential direction with respect to the direction along the tire radial direction of the tire side surface, and the ratio L / H of the center-to-center distance L between the tops of adjacent ridges to the height H of the ridge is 2 or more and 6 or less. When the upper side is the mountain side portion and the lower side is the valley side portion with the center in the height H direction of the ridge as the boundary, 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. A pneumatic tire.

3. A tire side surface which is on the inner side in the tire radial direction from the ground contact end of the tread and on the outer side in the tire radial direction from the rim line, and is formed on the outer side surface in the tire axial direction, and includes ridges which are a plurality of rib-like protrusions regularly arranged in the tire circumferential direction. Each of the plurality of ridges extends outward in the tire radial direction within a range inclined 60 degrees on both sides in the tire circumferential direction with respect to the direction along the tire radial direction of the tire side surface, and the ratio L / H of the center-to-center distance L between the tops of adjacent ridges to the height H of the ridge is 2 or more and 6 or less. The plurality of ridges are formed to protrude from the bottom surface of a recess which is recessed toward the inner surface side of the tire from the sidewall reference surface on the tire side surface, and the top of each of the plurality of ridges protrudes from the sidewall reference surface. A pneumatic tire.

4. The concave portion is an annular concave portion provided along the tire circumferential direction on the tire side surface. The pneumatic tire according to claim 3.

5. 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 the direction orthogonal to the extending direction of the ridge is 1.5 times or more and 3.5 times or less of the height H of the ridge. The pneumatic tire according to any one of claims 1 to 3.

6. A plurality of the ridges are formed within a tire radial range of 5% or more and 65% or less when the tire radial position of the rim line is 0 and the tire section height is 100 on the tire side surface. The pneumatic tire according to any one of claims 1 to 3.

7. A mold for molding a pneumatic tire for molding the pneumatic tire according to any one of claims 1 to 4, The mold for molding a pneumatic tire having a plurality of concave portions corresponding to the plurality of ridges on the molding surface.

Images