JP7230731B2 - pneumatic tire - Google Patents

Description

The present invention relates to pneumatic tires.

The brand may be displayed on the side of the pneumatic tire. In order to improve the visibility and appearance of the display of the brand, etc., there is a demand for a tire with high self-cleaning performance that can easily wash away deposits on the tire side due to rainfall or vehicle washing. If an organic cleaning agent is used, the side rubber may deteriorate and cause cracks, so there is a need to improve cleaning performance with water alone. In addition, from the viewpoint of considering the impact on the environment caused by the outflow of the cleaning agent, it is useful to use a tire having high cleaning performance with only water without using the cleaning agent.

Patent Literature 1 discloses a pneumatic tire in which the visibility of a decorative portion provided on a sidewall portion is enhanced. Further, Patent Literature 2 discloses a pneumatic tire in which ridges are provided on the sidewall portion to suppress degradation in appearance due to cracks occurring on the rubber surface.

Japanese Patent No. 3422715 Japanese Patent No. 4371625

Patent Documents 1 and 2 do not consider compatibility between visibility performance and cleaning performance, and there is room for improvement in improving both visibility performance and cleaning performance.

The present invention has been made in view of the above, and an object thereof is to provide a pneumatic tire capable of improving both visibility performance and cleaning performance.

In order to solve the above-described problems and achieve the object, a pneumatic tire according to one aspect of the present invention includes a tread portion, a sidewall portion, and a bead portion, the sidewall A serration region is provided in a predetermined region of the portion, the serration region is formed by arranging a plurality of ridges, the plurality of ridges are parallel to each other and periodically protrude from the base surface, and the plurality of ridges Length Lr is the length along the contour of the ridge per cycle in a cross-sectional view along the direction orthogonal to the extending direction, and length is the length of one cycle of the plurality of ridges along the base surface. Lb, the ratio Lr/Lb of the length Lr to the length Lb is 1.2 or more and 2.0 or less, the length Lb is 0.5 mm or more and 0.7 mm or less, and the tire meridian In the cross section, the ratio LH/SH of the length LH in the tire radial direction of the range of the serration region in the tire radial direction to the tire section height SH is 0.2 or more and 0.4 or less, and in the tire meridional section, When the height along the tire radial direction from the measurement point of the rim diameter of the rim on which the pneumatic tire is mounted to the position inside the tire radial direction of the serration region is AH, the height relative to the tire cross-sectional height SH The ratio AH/SH of the height AH is 0.3 or more and 0.5 or less, and the plurality of ridges have curved portions whose curvature changes near both ends, and the length of the ridges is 10% of the length of the both ends. In the 80% length of the central portion excluding the length, the length direction of the tangential line to the curved portion is the extending direction of the ridge, and the direction toward the tire radial direction outer side is used as a reference, the ridge with respect to the tire radial direction is within a range of ±20 degrees with respect to the tire radial direction .

In a cross-sectional view along a direction orthogonal to the extending direction of the ridges, it is preferable that an opening width La between the adjacent ridges is 0.15 mm or more and 0.35 mm or less.

A ratio La/Lb of the opening width La to the length Lb is preferably 0.3 or more and 0.6 or less.

The base surface has a flat portion having no unevenness, the flat portion is straight in a cross-sectional view along a direction orthogonal to the extending direction of the ridge, and the length of the straight line is It is preferably 0.15 mm or more.

A ratio RH/Lb of the height RH from the base surface to the maximum projecting position of the ridge to the length Lb is preferably 0.11 or more and 0.3 or less.

It is preferable that the angle θr between the flat portion of the base surface having no unevenness and the wall surface of the ridge is 60 degrees or more and 85 degrees or less.

Preferably, the surface of the ridge-contouring member is hydrophilic.

The arithmetic mean roughness Ra of the rubber on the surface of the ridge is preferably 0.1 μm or more and 5 μm or less.

It is preferable that the base surface is a surface that is recessed from the tire profile toward the inner cavity of the tire.

A first protrusion extending in the tire circumferential direction at a position outside the serration region in the tire radial direction, and a second protrusion extending in the tire circumferential direction at a position inside the serration region in the tire radial direction. It is preferable to have

It is preferable that the protrusion height from the tire profile of the said 1st convex part and the said 2nd convex part is 0.7 mm or less.

It is preferable that the ridge is trapezoidal in a cross-sectional view along a direction orthogonal to the extending direction of the ridge.

According to the pneumatic tire according to the present invention, it is possible to improve both visibility performance and cleaning performance.

FIG. 1 is a meridional cross-sectional view showing essential parts of a pneumatic tire according to an embodiment. FIG. 2 is a side view of the pneumatic tire according to the embodiment of the invention. FIG. 3 is a cross-sectional view showing an example of ridges provided in the serration region in FIG. FIG. 4 is a cross-sectional view showing an example of ridges provided in the serration region in FIG. FIG. 5 illustrates the hydrophilicity of the surface of the ridge contouring member. FIG. 6 illustrates the hydrophilicity of the surface of the ridge contouring member. 7 is an enlarged view of a part of FIG. 4. FIG. FIG. 8 is a diagram showing an example of a serration area. FIG. 9 is a diagram showing an example of a serration area. FIG. 10 is a diagram showing an example of a serration area. FIG. 11 is a diagram showing an example of a serration area. FIG. 12 is a diagram showing an arrangement example of ridges in the serration region. FIG. 13 is a diagram showing an arrangement example of ridges in the serration region. FIG. 14 is a diagram showing examples of ridge shapes. FIG. 15 is a diagram showing examples of ridge shapes.

BEST MODE FOR CARRYING OUT THE INVENTION Below, embodiments of the present invention will be described in detail based on the drawings. In the description of each embodiment below, the same reference numerals are given to components that are the same as or equivalent to those of other embodiments, and description thereof will be simplified or omitted. The present invention is not limited by each embodiment. In addition, the components of each embodiment include those that can be easily replaced by those skilled in the art, or those that are substantially the same. A plurality of modified examples described in this embodiment can be arbitrarily combined within the scope obvious to those skilled in the art.

In the following description, the tire width direction refers to a direction parallel to the rotation axis (not shown) of the pneumatic tire 1 . The term "outer side in the tire width direction" refers to the side away from the tire equatorial plane (tire equator line) in the tire width direction. The tire circumferential direction is a circumferential direction around the rotation axis. Moreover, the tire radial direction refers to a direction perpendicular to the rotation axis. The inner side in the tire radial direction means the side facing the rotation axis in the tire radial direction, and the outer side in the tire radial direction refers to the side away from the rotation axis in the tire radial direction. The tire equatorial plane is a plane perpendicular to the rotation axis and passing through the center of the tire width of the pneumatic tire 1 . Further, the tire width is the width in the tire width direction between the outer portions in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane in the tire width direction. A tire equator line is a line along the circumferential direction of the pneumatic tire 1 on the tire equatorial plane.

[Pneumatic tire]
FIG. 1 is a meridional cross-sectional view showing essential parts of a pneumatic tire according to an embodiment. A pneumatic tire 1 shown in FIG. 1 has a tread portion 2 disposed at the outermost portion in the tire radial direction when viewed in a meridional cross section. The surface of the tread portion 2 , that is, the portion that comes into contact with the road surface when the vehicle (not shown) on which the pneumatic tire 1 is mounted has a tread surface 3 . A plurality of circumferential main grooves 25 extending in the tire circumferential direction are formed in the tread surface 3 . A plurality of land portions 20 are defined on the tread surface 3 by the circumferential main grooves 25 . Grooves other than the circumferential main grooves 25 may be formed in the tread surface 3 . For example, lug grooves (not shown) extending in the tire width direction, narrow grooves (not shown) different from the circumferential direction main grooves 25, and the like may be formed on the tread surface 3 .

Shoulder portions 8 are positioned at both ends of the tread portion 2 in the tire width direction. A sidewall portion 30 is provided inside the shoulder portion 8 in the tire radial direction. The sidewall portions 30 are arranged at two locations on both sides of the pneumatic tire 1 in the tire width direction. A surface of the sidewall portion 30 is formed as a tire side portion 31 . The tire side portions 31 are located on both sides in the tire width direction. The two tire side portions 31 face opposite sides of the tire equatorial plane CL in the tire width direction.

The tire side portion 31 in this case refers to a surface that is uniformly continuous in a range outside the ground contact edge T of the tread portion 2 in the tire width direction and outside the rim check line R in the tire radial direction. The ground contact edge T is the tread surface of the tread portion 2 of the pneumatic tire 1 when the pneumatic tire 1 is mounted on a regular rim, filled with regular internal pressure, and 70% of the regular load is applied. In the area where 3 contacts the road surface, both outermost ends in the tire width direction are continuous in the tire circumferential direction. In addition, the rim check line R is a line for checking whether or not the rim assembly of the tire is performed normally. It is shown as an annular convex line continuous in the tire circumferential direction along a portion located outside in the tire radial direction and near the rim flange.

A non-grounded area at the connection between the profile of the tread portion 2 and the profile of the sidewall portion 30 is called a buttress portion. The buttress portion 32 forms a side wall surface of the shoulder portion 8 on the outer side in the tire width direction.

Note that the regular rim means "applicable rim" defined by JATMA (Japan Automobile Tire Manufacturers Association), "design rim" defined by TRA, or "measuring rim" defined by ETRTO. Further, the regular internal pressure means the maximum air pressure specified by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "INFLATION PRESSURES" specified by ETRTO. Further, the normal load means the maximum load capacity defined by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined by TRA, or the "LOAD CAPACITY" defined by ETRTO.

The bead portion 10 is positioned inside in the tire radial direction of each sidewall portion 30 positioned on both sides in the tire width direction. The bead portions 10 are arranged at two locations on both sides of the tire equatorial plane CL, similarly to the sidewall portions 30 . A bead core 11 is provided in each bead portion 10 , and a bead filler 12 is provided outside the bead core 11 in the tire radial direction.

A plurality of belt layers 14 are provided inside the tread portion 2 in the tire radial direction. The belt layer 14 is provided by laminating a plurality of cross belts 141 and 142 and a belt cover 143 . Of these, the cross belts 141 and 142 are constructed by coating a plurality of belt cords made of steel or organic fiber material with coat rubber and rolling them, and have a belt angle of 20 degrees or more and 55 degrees or less in absolute value. Configured. In addition, the plurality of cross belts 141 and 142 have different belt cords defined as the inclination angles of the fiber directions of the belt cords with respect to the tire circumferential direction, and are laminated with the fiber directions of the belt cords intersecting each other. It is configured as a so-called cross-ply structure. The belt cover 143 is formed by rolling a plurality of cords made of steel or organic fiber material covered with a coat rubber, and has a belt angle of 0 degrees or more and 10 degrees or less in absolute value. The belt cover 143 is laminated on the outside of the cross belts 141 and 142 in the tire radial direction.

A carcass 13 containing radial ply cords is continuously provided on the inner side of the belt layer 14 in the tire radial direction and on the side of the tire equatorial plane CL of the sidewall portion 30 . The carcass 13 has a single-layer structure composed of one carcass ply or a multilayer structure composed of a plurality of laminated carcass plies, and is toroidally spanned between the bead cores 11 arranged on both sides in the tire width direction. It is passed and constitutes the frame of the tire. More specifically, the carcass 13 is arranged from one bead portion 10 to the other bead portion 10 of the bead portions 10 located on both sides in the tire width direction, and the bead so as to wrap the bead core 11 and the bead filler 12. At the portion 10, it is wound back along the bead core 11 to the outside in the tire width direction. The carcass ply of the carcass 13 is formed by coating a plurality of carcass cords made of steel or an organic fiber material such as aramid, nylon, polyester, rayon, etc. with a coating rubber and rolling the carcass ply. The absolute value of the carcass angle, which is the inclination angle of the cord in the fiber direction, is 80° or more and 95° or less.

A rim cushion rubber 17 that constitutes a contact surface of the bead portion 10 with the rim flange is disposed on the inner side in the tire radial direction and the outer side in the tire width direction of the wound portion of the bead core 11 and the carcass 13 in the bead portion 10 . An inner liner 15 is formed along the carcass 13 inside the carcass 13 or on the inner side of the carcass 13 in the pneumatic tire 1 .

[Serration area]
In FIG. 1, the pneumatic tire 1 has a buttress portion 32 with a convex portion B1 and a convex portion B2. A serration region H is between the convex portion B1 and the convex portion B2. The serration region H is located outside the maximum width position PW of the pneumatic tire 1 in the tire radial direction. The serration region H is formed by arranging a plurality of ridges as will be described later, and the plurality of ridges are arranged in parallel and periodically. A ratio LH/SH of the length LH in the tire radial direction of the range of the serration region H in the tire radial direction to the tire cross-section height SH is 0.2 or more and 0.4 or less.

Further, when the height along the tire radial direction from the measurement point of the rim diameter of the rim (not shown) on which the pneumatic tire 1 is mounted to the position inside the tire radial direction of the serration region H is AH, A ratio AH/SH of the height AH to the tire section height SH is 0.3 or more and 0.5 or less.

FIG. 2 is a side view of the pneumatic tire 1 according to the embodiment of the invention. 2 is a side view of the pneumatic tire 1, including a view taken along line AA of FIG. 1. FIG. In FIG. 2 , the serration region H is provided on the tire side portion 31 .

The tire side portion 31 is sometimes provided with a decorative portion for the purpose of improving the appearance of the pneumatic tire 1 and displaying various information. The decorative part may include various information such as a brand name, a logo mark, a product name, etc. for identifying the pneumatic tire 1 or for showing to the user.

[Cross-sectional shape of ridge]
3 and 4 are cross-sectional views showing examples of ridges provided in the serration region H in FIG. 3 and 4 are cross-sectional views along a direction perpendicular to the extending direction of the ridge. FIG. 3 is a cross-sectional view showing an example of one ridge 51. As shown in FIG. FIG. 4 is a cross-sectional view showing an example of adjacent ridges 51a and 51b.

In FIG. 3, the ridge 51 rises outward from the base surface 50 of the tire. The ridge 51 has a ridge-like convex shape and extends along the tire side portion 31 . The ridge 51 has a substantially trapezoidal shape in a cross-sectional view along a direction orthogonal to the extending direction. The substantially trapezoidal shape is a shape having a flat portion on the upper base, ie, the top surface U, without unevenness. If at least a portion of the top surface U is a flat portion without irregularities, it can be regarded as a substantially trapezoid, and the entire top surface U need not be a flat portion without irregularities. The ridge 51 may be arcuate as indicated by the one-dot chain line or may be triangular as indicated by the two-dot chain line in a cross-sectional view. When the shape of the ridge 51 is substantially trapezoidal in a cross-sectional view along the direction orthogonal to the extending direction, the surface area of the ridge can be increased compared to other shapes (arc, triangle) even if the height is the same. Hydrophilicity can be enhanced. Even if the trapezoid is trapezoidal, the lower base is aligned with the base surface 50, so that water can enter the base surface 50 more easily than when the upper base is aligned with the base surface 50, and hydrophilicity and washability can be improved.

Also, the surfaces of the members forming the contours of the ridges 51a and 51b are hydrophilic. By providing the ridges 51a and 51b on a hydrophilic member, the hydrophilicity can be enhanced. 5 and 6 are diagrams illustrating the hydrophilicity of the surfaces of the members defining the ridges 51a, 51b. As shown in FIG. 5, a flat base surface 50 without ridges 51 is assumed. At this time, it is assumed that the contact angle θs between the water droplet WD and the base surface 50 is less than 90 degrees and the base surface 50 is hydrophilic. As shown in FIG. 6, the contact angle .theta.s is smaller than in FIG. 5 due to the provision of a plurality of ridges 51 protruding from the base surface 50 to the outside of the tire. Therefore, the surface of the member, including the basal surface 50 and the ridges 51, exhibits a higher hydrophilicity than the flat basal surface 50. FIG.

The arithmetic mean roughness Ra of the rubber on the surfaces of the ridges 51a and 51b is preferably 0.1 μm or more and 5 μm or less. Hydrophilicity can be enhanced by optimizing the surface roughness. Hydrophilicity is increased by increasing the surface roughness. However, if the roughness is too large, it becomes difficult for water to enter into the concave portions of the roughness, and the hydrophilicity deteriorates. More preferably, the arithmetic mean roughness Ra is 0.2 μm or more and 4 μm or less. The arithmetic mean roughness Ra is measured according to JIS B0601.

Returning to FIG. 4 , the base surface 50 is a surface recessed from the profile line 52 toward the tire inner cavity. A profile line is a contour line that smoothly connects the buttress portion 32 and the bead portion 10 in the meridional section of the tire. A profile line is constituted by a single or multiple arcs. A profile line is defined exclusive of partial irregularities. The buttress portion 32 is a non-contacting area at the connection portion between the profile of the tread portion 2 and the profile of the sidewall portion, and constitutes the sidewall surface of the shoulder portion 8 on the outer side in the tire width direction.

As shown in FIG. 4, the plurality of ridges 51a, 51b protrude from the base surface 50 toward the outside of the tire. Here, Lr is the length along the contour of the ridges per period in a cross-sectional view along the direction orthogonal to the extending direction of the plurality of ridges 51a and 51b. The length Lr is the peripheral length along the contour of the ridges 51 per cycle of the ridges 51 in a cross-sectional view along the direction perpendicular to the extending direction of the ridges 51 . That is, when focusing on the ridge 51a, the length Lr is the total length of the length L1 of the base surface, the length L2 of the wall surface 53, the length L3 of the top surface U, and the length L4 of the wall surface 53. be.

Also, the length of one cycle of the plurality of ridges 51a and 51b along the base plane 50 is defined as Lb. That is, the length Lb is the length of one pitch of the ridges 51a and 51b. The ratio Lr/Lb of the length Lr to the length Lb is preferably 1.2 or more and 2.0 or less. By increasing the surface area of the ridge, the hydrophilicity of the serration region H can be improved, and the self-cleaning effect of the sidewall portion 30 when sludge adheres can be enhanced. If the ratio Lr/Lb exceeds 2.0 by complicating the cross-sectional shape of the ridge and making it finer, water will not enter the base surface 50 and the hydrophilicity will decrease, which is not preferable. If the ratio Lr/Lb is less than 1.2, the effect of improving the cleaning performance by improving the hydrophilicity is small, which is not preferable.

The length Lb is preferably 0.5 mm or more and 0.7 mm or less. If the length Lb is less than 0.5 mm, it becomes difficult for water to enter the base surface 50, and the hydrophilicity is lowered, which is not preferable. If the length Lb exceeds 0.7 mm, the washing performance is lowered, which is not preferable. If the length Lb is less than 0.5 mm, it becomes difficult for water to enter to the base surface 50, and the hydrophilicity and washing performance are lowered, which is not preferable.

Also, the length Lb is more preferably 0.52 mm or longer, and even more preferably 0.54 mm or longer. If the length Lb is 0.52 mm or more, good results can be obtained with respect to visibility performance and cleaning performance. Moreover, if the length Lb is 0.54 mm or more, better results can be obtained with respect to visibility performance and cleaning performance.

In FIG. 4, the opening width La between adjacent ridges is preferably 0.15 mm or more and 0.35 mm or less in a cross-sectional view along a direction perpendicular to the extending direction of the ridges. If the value of the opening width is within this range, good results can be obtained in terms of visibility performance and cleaning performance. The opening width La is the distance between boundary points between the wall surface 53 of the ridge and the upper surface of the ridge in a cross-sectional view along the direction orthogonal to the extending direction of the ridge.

In some cases, the top surfaces U of the ridges 51a and 51b and the wall surfaces 53 of the ridges 51a and 51b are connected by curved lines, and the boundaries between the top surfaces U and the wall surfaces 53 are not clear. In this case, the opening width La is measured based on the intersection of a line extending the straight portion of the top surface U of the ridge 51 and a line extending the straight portion of the wall surface 53 of the ridge 51 .

7 is an enlarged view of a part of FIG. 4. FIG. FIG. 7 is an enlarged view of the space between the ridges 51a and 51b in FIG. FIG. 7 is a diagram showing an example in which the top surfaces U of the ridges 51a and 51b and the wall surfaces 53 of the ridges 51a and 51b are connected by curved lines in a cross-sectional view in a direction perpendicular to the extending direction of the ridges 51a and 51b. be. As shown in FIG. 7, when the boundary between the top surfaces U of the ridges 51a and 51b and the wall surface 53 is not clear, a line obtained by extending the straight line portion of the top surface U of the ridge 51 and the straight line portion of the wall surface 53 of the ridge 51 are separated. The opening width La is measured based on the intersection point PA with the extended line.

Returning to FIG. 4, the ratio La/Lb of the opening width La to the length Lb is preferably 0.3 or more and 0.6 or less. If the value of the ratio La/Lb is within this range, good results can be obtained in terms of visibility performance and cleaning performance.

Moreover, the height RH from the base surface 50 to the maximum projecting position of the ridges 51a and 51b is preferably 0.08 mm or more and 0.15 mm or less. As described above, the length Lb is preferably 0.5 mm or more and 0.7 mm or less, so the ratio RH/Lb of the height RH to the length Lb is 0.11 or more and 0.3 or less. is preferred. If the value of the ratio RH/Lb is within this range, good results can be obtained in terms of visibility performance and cleaning performance.

As shown in FIG. 4, the base surface 50 has a flat portion without irregularities. The flat portion of the base surface 50 is straight in cross-sectional view along the direction perpendicular to the extending direction of the ridges 51a and 51b. Even if dirt adheres to the base surface 50, the presence of the flat portion allows water to enter the base surface 50 and wash away the dirt together with the water. The length of the straight line of the base surface 50 in a cross-sectional view is preferably 0.15 mm or more. If the length L1 of the straight line of the base surface 50 is 0.15 mm or more, good results can be obtained in terms of visibility performance and cleaning performance.

In some cases, the base surface 50 and the wall surfaces 53 of the ridges 51a and 51b are connected by curved lines, and the boundary between the base surface 50 and the wall surfaces 53 is not clear. In this case, as shown in FIG. 7, the length L1 is measured with reference to an intersection point PB between a line extending the straight line of the base surface 50 and a line extending the straight line portion of the wall surface 53 of the ridge 51 .

Returning to FIG. 4, the angle θr between the flat portion of the base surface 50 and the wall surfaces 53 of the ridges 51a and 51b is preferably 60 degrees or more and 85 degrees or less. If the angle θr is within this range, good results can be obtained with respect to visibility performance and cleaning performance. Hydrophilicity can be enhanced by appropriately setting the angle θr. If the angle .theta.r is larger than 85 degrees, it becomes difficult for water to enter the base surface 50, and the hydrophilicity is rather deteriorated. If the angle .theta.r is less than 60 degrees, the surface area will not be large and sufficient improvement in hydrophilicity will not be obtained. More preferably, the angle θr is 70 degrees or more and 80 degrees or less.

In some cases, the base surface 50 and the wall surfaces of the ridges 51a and 51b are connected by curved lines, and the boundary between the base surface 50 and the wall surfaces 53 is not clear. In this case, as shown in FIG. 7, the angle .theta.r is measured with reference to an intersection point PB between a line extending the straight line of the base surface 50 and a line extending the straight line portion of the wall surface 53 of the ridge 51. As shown in FIG. Alternatively, the angle θr may be obtained by measuring the angle between a line extending the straight line of the base surface 50 and a line extending the straight portion of the wall surface 53 of the ridge 51 and subtracting the angle from 180 degrees.

[Serration area shape, etc.]
8 to 11 are diagrams showing examples of the serration region H. FIG. 8 to 11 show enlarged portions of the serration region H. FIG. In the example of the serration region H shown in FIG. 8, the length LH of the serration region H in the tire radial direction is uniform in the tire circumferential direction. Further, as shown in FIG. 9, the length LH in the tire radial direction may not be uniform in the tire circumferential direction due to the notch K in the serration region H. As shown in FIG.

Further, as shown in FIG. 10, the serration region H may include plane portions F1, F2, F3, F4 and F5 in which no ridge is provided. Each plane portion F1-F5 may be a surface level with the tire profile. Each plane portion F1-F5 may be a surface with a different height than the tire profile, for example a surface with the same height as the base surface. As shown in FIG. 11, the serration region H may have a cutout portion K, and the serration region H may have plane portions F1 to F5.

12 and 13 are diagrams showing an arrangement example of ridges in the serration region H. FIG. In FIGS. 12 and 13, each of the plurality of ridges provided within the serration region H is indicated by lines. In FIGS. 12 and 13, it is assumed that ridges not drawn are provided in the circumferential direction of the tire as well as ridges clearly drawn.

As shown in FIG. 12, serration region H is provided with a plurality of ridges 51 . Each ridge 51 is arranged parallel to adjacent ridges 51 . Here, "parallel" means that the distance between adjacent ridges is constant in plan view. If the ridge has a curved portion, as shown in FIG. 12, parallel means that the distance between adjacent ridges along the normal to the curved portion is constant. However, even if the ridges are not perfectly parallel, if the difference is within 10% of the distance to the adjacent ridges, the distance is considered constant, that is, they are parallel.

In FIG. 12 , the serration region H is defined between an outer virtual line S1 connecting the radially outer ends 51T1 of the ridges 51 and an inner virtual line S2 connecting the inner ends 51T2 of the ridges 51 in the tire radial direction. is the area of The distance between the outer virtual line S1 and the inner virtual line S2 is the length LH of the serration region H in the tire radial direction.

As shown in FIG. 13, when the ridges have different lengths, an outer virtual line S1 connecting the radially outer ends 51T1 of the ridges 51 and an inner virtual line S2 connecting the inner ends 51T2 of the ridges 51 in the tire radial direction. is the serration region H. As shown in FIG. 13, when the length of each ridge is not the same, the distance between the outermost position of the outer virtual line S1 in the tire radial direction and the innermost position of the inner virtual line S2 in the tire radial direction, that is, the tire The maximum width in the radial direction is the length LH of the serration region H in the tire radial direction.

[Shape of ridge]
14 and 15 are diagrams showing examples of the shape of the ridge 51. FIG. 14 and 15 are enlarged views of one ridge 51 in the serration region.

In FIG. 14, the angle of the extending direction of the ridge 51 with respect to the tire radial direction is θc. Here, regarding the angle θc, the clockwise angle with respect to the direction toward the outside in the tire radial direction is defined as a plus (+) angle, and the counterclockwise angle with respect to the direction toward the outside in the tire radial direction is defined as a minus (−) angle. be the angle of As shown in FIG. 14, when the ridge 51 has a curved portion, the lengthwise direction of the tangent line ST to the curved portion is the extending direction of the ridge 51 .

The angle θc is preferably an angle within a range of ±20 degrees with respect to the radially outward direction of the tire. By extending the extending direction of the ridge 51 at an angle close to the tire radial direction, the water adhering to the tire surface easily spreads in the tire radial direction, and the adhered substances on the tire surface can be easily washed away. The angle θc is more preferably an angle within a range of ±10 degrees with respect to the tire radial direction.

The angle θc does not need to be within the above range over the entire length of the ridge 51 from the end 51T1 to the end 51T2. That is, regarding the imaginary line S51 connecting the ends 51T1 and 51T2 of the ridge 51 with a straight line, the length L80 of 80% of the central portion excluding the length L10 of 10% of both ends of the entire length L51 , and the angle θc may be within the above range.

In the ridge 51' shown in FIG. 15, the curvature of the curved portion greatly changes near both ends. As for the ridge 51' shown in FIG. 15, the imaginary line S51' connecting the end 51T1 and the end 51T2 with a straight line is 80% of the central portion of the length L51 excluding the length L10 of 10% of both ends. In the length L80, the angle θc may be an angle within the above range.

[Convex part]
Returning to FIG. 1 , in the tire meridional cross-sectional view, the protrusion B1 is positioned at the outer end of the serration region H in the tire radial direction, and the protrusion B2 is positioned at the inner end of the serration region H in the tire radial direction. The convex portion B1 extends in the tire circumferential direction at a position on the outer side of the serration region H in the tire radial direction. The convex portion B2 extends in the tire circumferential direction at a position on the inner side of the serration region H in the tire radial direction. The convex portion B1 and the convex portion B2 extend in the tire circumferential direction while connecting the ends of the ridge 51 described with reference to FIGS. 12 and 13 . The mold is provided with recesses and air vent holes to discharge air between the green tire and the mold during vulcanization molding of the tire. Therefore, the protrusions B1 and B2 are formed at positions corresponding to the recesses of the mold. If the depth of the concave portion of the mold is not uniform, the protrusion heights of the protrusions B1 and B2 from the tire profile will not be uniform. Efficient discharge of air between the green tire and the mold during vulcanization molding of the tire by periodically changing the protrusion heights of the protrusions B1 and B2 from the tire profile in the tire circumferential direction. can be done.

When the pneumatic tire 1 is mounted on a regular rim and filled with regular internal pressure, the projection height BH of the protrusions B1 and B2 from the tire profile is 0.7 mm or less. By reducing the height of the protrusion extending in the tire circumferential direction, the water flow can smoothly flow out of the tire without being blocked, and the cleaning performance is not lowered. In addition, it is more preferable that the protrusion height from the tire profile of convex part B1 and convex part B2 is 0.2 mm or more and 0.5 mm or less.

[Example]
In this example, a plurality of types of pneumatic tires under different conditions were tested for contact angle, cleaning performance, and visibility performance, which are indicators of hydrophilicity (see Tables 1 to 4). . In these tests, 245/45R20 103W (20×8J) pneumatic tires were mounted on specified rims and filled with specified air pressure.

As for the contact angle, the water contact angle of the obtained serrated region sample was measured with a measuring instrument. The measuring instrument used for the measurement is DM-901 manufactured by Kyowa Interface Science Co., Ltd. Measurements were made in accordance with JIS R3257. 2 [μl] of pure water was dropped to form a water drop, and the contact angle of the water drop 30 seconds after dropping was measured by the θ/2 method.

Regarding cleaning performance, pneumatic tire 1 was mounted on a 3000 cc rear-wheel drive vehicle, and after running 40 km on a general road and 100 km on an expressway in rainy weather, the tires were completely dried and washed with a high-pressure cleaner ( The tire was washed for 30 seconds with a water pressure of 100 bar and a flow rate of 300 L/h. The amount of dirt adhering to the tire side surface after washing was evaluated by sensory evaluation by three evaluators. Appearance with black luster before the start of the test run was given a full score of 10 points, and the smaller the degree of gray or white and the closer to black luster, the higher the score, and conversely, the higher the degree of gray or white, the lower the score. was based on the average value of the total scores of three persons. Scores are given in increments of 0.5 points, and a higher score closer to 10 points is better.

As for the visibility performance, a brand display was provided in the serration area, and the visibility of the brand display was visually evaluated. The evaluation results were calculated using an index value with the pneumatic tire of the conventional example set to "100". The higher the number, the better the visibility of the brand display.

In the pneumatic tires of Examples 1 to 38 shown in Tables 1 to 4, the ratio Lr/Lb of the length Lr to the length Lb of one cycle of the ridge is 1.2 or more and 2.0 or less. and otherwise, the length Lb is 0.5 mm or more and 0.7 mm or less, the opening width La is 0.15 mm or more and 0.35 mm or less, and the ratio La/Lb is 0.3 or more and 0.6 or less, those where the linear length of the flat portion of the basal plane is 0.15 mm or more and those where it is not, and the ratio RH/Lb of 0.11 or more and 0.11. 3 or less and not, LH/SH ratio of 0.2 to 0.4 and not, AH/SH ratio of 0.3 to 0.5 and not , the angle θr is 60 degrees or more and 85 degrees or less, the angle θc is within the range of ±20 degrees with respect to the tire radial direction or not, the arithmetic mean of the rubber on the surface of the ridge The roughness Ra is 0.1 μm or more and 5 μm or less, and the protrusion height of the first protrusion B1 and the second protrusion B2 from the tire profile is 0.7 mm or less. It is a thing.

The tire of the conventional example in Table 1 has a ratio Lr/Lb of 1.2, a length Lb of 1.0 mm, an opening width La of 0.13 mm, a ratio La/Lb of 0.13, and a linear length of the flat portion. 0.03 mm, RH/Lb ratio 0.4, LH/SH ratio 0.15, AH/SH ratio 0.6, angle θr 55 degrees, angle θc 45 degrees, surface roughness Ra 10 μm, and the height BH of the convex portion is 0.8 mm. The tire of Comparative Example 1 in Table 1 has a ratio Lr/Lb of 1.8, a length Lb of 0.6 mm, an opening width La of 0.13 mm, a ratio La/Lb of 0.22, and a straight line of the flat portion. The length is 0.03 mm, the ratio RH/Lb is 0.3, the ratio LH/SH is 0.15, the ratio AH/SH is 0.6, the angle θr is 55 degrees, the angle θc is 45 degrees, and the surface roughness Ra is 10 μm, and the height BH of the convex portion is 0.8 mm. The tire of Comparative Example 2 in Table 1 has a ratio Lr/Lb of 1.4, a length Lb of 0.4 mm, an opening width La of 0.4 mm, a ratio La/Lb of 1.0, and a straight line of the flat portion. The length is 0.3 mm, the ratio RH/Lb is 0.4, the ratio LH/SH is 0.15, the ratio AH/SH is 0.6, the angle θr is 55 degrees, the angle θc is 45 degrees, and the surface roughness Ra is 10 μm, and the height BH of the convex portion is 0.8 mm.

Referring to Tables 1 to 4, when the ratio Lr/Lb of the length Lr is 1.2 or more and 2.0 or less, when the length Lb is 0.5 mm or more and 0.7 mm or less, the opening width La is When the ratio La/Lb is 0.3 or more and 0.6 or less When the straight length of the flat portion of the basal plane is 0.15 mm or more When the ratio RH /Lb is 0.11 or more and 0.3 or less, if the ratio LH/SH is 0.2 or more and 0.4 or less, if the ratio AH/SH is 0.3 or more and 0.5 or less, the angle When θr is 60 degrees or more and 85 degrees or less, and when the angle θc is within the range of ±20 degrees with respect to the tire radial direction, the arithmetic mean roughness Ra of the rubber on the surface of the ridge is 0.1 μm or more and 5 μm or less. In some cases, it can be seen that good results are obtained when the protrusion height of the first protrusion B1 and the second protrusion B2 from the tire profile is 0.7 mm or less.

1 pneumatic tire 2 tread portion 3 tread surface 8 shoulder portion 10 bead portion 11 bead core 12 bead filler 13 carcass 14 belt layer 15 inner liner 17 rim cushion rubber 20 land portion 25 circumferential main groove 30 sidewall portion 31 tire side portion 32 Buttress portion 50 Base surface 51, 51a, 51b Ridge 52 Profile line 53 Wall surface 141 Cross belt 143 Belt cover B1, B2 Convex portion CL Tire equatorial plane F1 to F5 Plane portion H Serration area R Rim check line T Ground contact edge

Claims (12)

A pneumatic tire comprising a tread portion, a sidewall portion, and a bead portion,
A serration region is provided in a predetermined region of the sidewall portion,
The serration region is formed by arranging a plurality of ridges,
the plurality of ridges protrude from the base surface in parallel and periodically with adjacent ridges ;
Lr is the length along the contour of the ridges per cycle in a cross-sectional view along the direction orthogonal to the extending direction of the plurality of ridges, and the length of one cycle of the plurality of ridges along the base surface is When the length is the length Lb, the ratio Lr/Lb of the length Lr to the length Lb is 1.2 or more and 2.0 or less,
The length Lb is 0.5 mm or more and 0.7 mm or less,
In the tire meridional section, the ratio LH/SH of the tire radial length LH of the tire radial direction range of the serration region to the tire section height SH is 0.2 or more and 0.4 or less,
In the tire meridional section, when the height along the tire radial direction from the measurement point of the rim diameter of the rim on which the pneumatic tire is mounted to the radially inner position of the serration region is AH, the tire section height is The ratio AH/SH of the height AH to the height SH is 0.3 or more and 0.5 or less,
The plurality of ridges have curved portions whose curvature changes near both ends,
In 80% of the length of the central portion excluding 10% of the length of the both ends, the length direction of the tangential line to the curved portion is the extending direction of the ridge,
The angle θc of the extending direction of the ridge with respect to the tire radial direction is within a range of ±20 degrees with respect to the tire radial direction, with reference to the radially outward direction of the tire.
pneumatic tires. The pneumatic tire according to claim 1, wherein an opening width La between the adjacent ridges is 0.15 mm or more and 0.35 mm or less in a cross-sectional view along a direction orthogonal to the extending direction of the ridges. The pneumatic tire according to claim 2, wherein a ratio La/Lb of said opening width La to said length Lb is 0.3 or more and 0.6 or less. The base surface has a flat portion that does not have unevenness,
The flat portion is straight in a cross-sectional view along a direction perpendicular to the extending direction of the ridge,
The pneumatic tire according to any one of claims 1 to 3, wherein the straight line has a length of 0.15 mm or more. 5. The method according to any one of claims 1 to 4, wherein a ratio RH/Lb of the height RH from the base surface to the maximum projecting position of the ridge to the length Lb is 0.11 or more and 0.3 or less. Pneumatic tires as described. The air pump according to any one of claims 1 to 5, wherein an angle θr between a flat portion of the base surface having no unevenness and the wall surface of the ridge is 60 degrees or more and 85 degrees or less. tire. 7. The pneumatic tire according to any one of claims 1 to 6 , wherein the surface of the ridge contouring member is hydrophilic. The pneumatic tire according to any one of claims 1 to 7 , wherein an arithmetic mean roughness Ra of rubber on the surface of the ridge is 0.1 µm or more and 5 µm or less. The pneumatic tire according to any one of claims 1 to 8 , wherein the base surface is a surface recessed from the tire profile toward the inner cavity side of the tire. A first protrusion extending in the tire circumferential direction at a position outside the serration region in the tire radial direction, and a second protrusion extending in the tire circumferential direction at a position inside the serration region in the tire radial direction. The pneumatic tire according to any one of claims 1 to 9 , comprising: 11. The pneumatic tire according to claim 10 , wherein the first protrusion and the second protrusion each have a protrusion height of 0.7 mm or less from the tire profile. The pneumatic tire according to any one of claims 1 to 11 , wherein the ridge is trapezoidal in a cross-sectional view along a direction perpendicular to the extending direction of the ridge.

Images