Pneumatic tires

Abstract

To suppress the formation of a bear.SOLUTION: In a pneumatic tire 10 of an embodiment, a spiral pattern 28 is provided in a pattern formation area 18 that is provided on a surface of a side wall 16. In the spiral pattern 28, a protrusive streak 32 protruding with respect to a reference plane 30 of the pattern formation area 18, and a recessed streak 34 depressed with respect to the reference plane 30 are alternately provided along a spiral while a height and a depth with respect to the reference plane 30 are gradually changed.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE An embodiment of the present invention relates to a pneumatic tire. [Background technology]

[0002] It is known that a pattern of serrations consisting of multiple small protruding stripes is provided on the surface of the sidewall of a pneumatic tire, thereby creating a contrast between dark and light areas due to light reflection between the area without the pattern and the area on the sidewall.

[0003] For example, Patent Document 1 discloses providing a pattern portion on the surface of a tire in which protrusions whose ridge lines have curved portions in a plan view are arranged in a nested manner having a center point. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-132296 A Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, conventional patterns are formed with multiple protruding ridges. In that case, a difference in the amount of rubber occurs between the parts without the pattern, which can result in bare ridges (underfill) during molding.

[0006] In view of the above, an object of an embodiment of the present invention is to provide a pneumatic tire capable of suppressing bare. [Means for solving the problem]

[0007] A pneumatic tire according to an embodiment of the present invention has a spiral pattern formed in a pattern forming area provided on the surface of a sidewall, and the spiral pattern is formed by alternating convex ridges that are raised relative to a reference surface of the pattern forming area and concave ridges that are recessed relative to the reference surface, the height and depth of which relative to the reference surface gradually changing, arranged along a spiral.

[0008] In one embodiment, the transition positions between the convex ribs and the concave ribs may be present at regular intervals along the length of the spiral.

[0009] In one embodiment, the transition positions between the convex ribs and the concave ribs may be present at regular angular intervals around a center point of the spiral.

[0010] In one embodiment, the transition position between the convex streak and the concave streak may be set according to an angle about a center point of the spiral, the angle being greater on the central side of the spiral than on the outer side of the spiral.

[0011] In one embodiment, the pattern may be a curved spiral.

[0012] In one embodiment, a region may be provided radially outward of the pattern forming region, in which a plurality of ridges extending in the radial direction of the tire are arranged at equal intervals around the tire, and the region has a dimension in the radial direction of the tire of 5 mm or more and 12 mm or less. Effect of the Invention

[0013] In the pneumatic tire according to the embodiment of the present invention, the pattern is composed not only of convex stripes but also of convex stripes and concave stripes, so that the amount of rubber can be equalized between the parts where the pattern is not provided, and the occurrence of bare spots during molding can be suppressed. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a half cross-sectional view of a pneumatic tire according to a first embodiment. [Diagram 2]1 is a side view of a pneumatic tire according to a first embodiment; [Diagram 3] FIG. 1 is a plan view of a pattern provided in a pattern forming area of ​​the first embodiment; [Figure 4] Cross-sectional view showing the cross-sectional shape along the spiral of the pattern [Diagram 5] A cross-sectional view of line VV in Figure 3 showing the cross-sectional shape of the pattern [Figure 6] FIG. 11 is a plan view showing a pattern switching position according to the second embodiment; [Figure 7] FIG. 13 is a plan view showing a pattern switching position according to the third embodiment; [Figure 8] A cross-sectional view showing a first modification of the convex and concave stripes constituting the pattern. [Figure 9] A cross-sectional view showing a second modification of the convex and concave stripes constituting the pattern. [Figure 10] A cross-sectional view showing a third modification of the convex and concave stripes constituting the pattern. [Figure 11] A cross-sectional view showing a fourth modification of the convex and concave stripes constituting the pattern. [Figure 12] A cross-sectional view showing a fifth modification of the convex and concave stripes constituting the pattern. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] [First embodiment] 1 to 5 are diagrams showing a pneumatic tire 10 according to a first embodiment. The pneumatic tire 10 includes a tread 12 forming a contact surface, a pair of left and right bead portions 14 fixed to a rim, and a pair of left and right sidewalls 16 interposed between the tread 12 and the bead portions 14. Fig. 1 is a half cross-sectional view of the pneumatic tire 10, taken along a meridian section including the tire rotation axis.

[0017] In the drawings, the symbol CL indicates the tire equatorial plane, which corresponds to the tire axial center. In this specification, the tire axial direction, also called the tire width direction, refers to the direction parallel to the tire rotation axis, and is indicated by the symbol AD ​​in the drawings. The tire radial direction refers to the direction perpendicular to the tire rotation axis, and is indicated by the symbol RD in the drawings. The tire circumferential direction refers to the direction of rotation around the tire rotation axis, and is indicated by the symbol CD in the drawings.

[0018] The internal structure of the pneumatic tire 10 is not particularly limited, and any known structure may be adopted. In general, a pneumatic tire has, as its internal structure, a pair of left and right bead cores, a carcass ply toroidally stretched between the pair of bead cores, and a belt disposed on the outer periphery of a crown portion of the carcass ply, and such an internal structure may be adopted.

[0019] A pattern forming region 18 is provided on the surface (i.e., outer surface) of at least one of the sidewalls 16. The surface of the sidewall 16 refers to the side surface of the tire that is located outside the surface of the tread 12 in the tire axial direction AD and is visible in the tire axial direction AD when the pneumatic tire 10 is mounted on a rim. The surface of the sidewall 16 is formed by vulcanizing and molding the sidewall rubber.

[0020] The pattern forming region 18 is provided in a part of the tire radial direction RD on the surface of the sidewall 16 in the tire cross-sectional shape shown in Fig. 1. The dimension of the pattern forming region 18 in the tire radial direction RD (hereinafter referred to as "height HA") is not particularly limited, but is preferably 0.05 to 0.6 times, and more preferably 0.1 to 0.35 times, the tire cross-sectional height H. Here, the tire cross-sectional height H refers to the vertical height (distance in the tire radial direction RD) from the bead heel E to the tire maximum diameter point, and is 1 / 2 of the difference between the tire outer diameter and the rim diameter.

[0021] The position of the pattern forming region 18 is not particularly limited, but it is preferable that the base diameter height HB is 0.45 to 0.65 times the tire cross-sectional height H. Here, the base diameter height HB refers to the vertical height from the midpoint that bisects the height HA to the bead heel E. The distance from the tire rotation axis to the midpoint that bisects the height HA is called the base diameter RS. In the example shown in FIG. 1, the pattern forming region 18 is provided at a position including the tire maximum width position PM. Here, the tire maximum width position PM refers to the position where the profile line of the tire surface in the sidewall 16 is farthest from the tire equatorial plane CL in the tire axial direction AD, and is the position in the tire radial direction RD.

[0022] The pattern formation region 18 may be formed over the entire circumference in the tire circumferential direction CD, but in this example, as shown in Fig. 2, it is formed in a part of the tire circumferential direction CD. In detail, a plurality of (here, two) curved band-shaped pattern formation regions 18, 18 are spaced apart in the tire circumferential direction CD. Marking regions 20, 20 are interposed between the plurality of pattern formation regions 18, 18, and a flat region 22 is provided between the pattern formation region 18 and the marking region 20. The pattern formation region 18, the marking region 20, and the flat region 22 form an annular decorative region 24 extending over the entire circumference in the tire circumferential direction CD.

[0023] The mark area 20 is an area where a mark 26 is formed. The mark 26 is composed of letters (including numbers), symbols, figures, or a combination of these, and may be, for example, various display information such as the tire manufacturer, brand, variety, and size. The mark 26 may be convex or concave, or may be provided concavely inside a convex border, and is not particularly limited. In the example shown in FIG. 2, marks 26 of "TOTO" and "TOTOTO" are provided in the mark area 20.

[0024] The flat region 22 is a region consisting of a flat surface on which the marking 26 and a pattern 28 described later are not formed. The length LB of the flat region 22 in the tire circumferential direction CD (length at the base radius RS) is not particularly limited, but is preferably 3 mm or more. The length LB is also preferably 0.6 times or less the length LA of the marking region 20 in the tire circumferential direction CD (length at the base radius RS). By making LB 0.6 times or less LA, the length of the pattern forming region 18 in the tire circumferential direction CD can be secured, enhancing the decorative effect.

[0025] As shown in Fig. 2, a plurality of patterns 28 are provided at intervals in the tire circumferential direction CD in the pattern formation region 18. In this example, the patterns 28 are provided so as to fill and decorate the spaces between the marking regions 20, 20 spaced apart in the tire circumferential direction CD. Therefore, the pattern formation region 18 can also be said to be a decorative region that fills the spaces between the marking regions 20, 20. Note that, although the plurality of patterns 28 all have the same shape in a plan view in the example of Fig. 2, they may have different shapes.

[0026] As shown in Fig. 3, the pattern 28 is formed in a spiral shape in a plan view. That is, the pattern 28 is formed by lines that spiral around a center point 38. Here, "plan view" refers to viewing the pattern 28 in a plane, and Fig. 3 is a diagram showing the pattern 28 in a plan view. As shown in Fig. 2, the center point 38 is disposed at a midpoint that bisects the height HA of the pattern formation region 18, which corresponds to the base diameter RS. The number of turns of the spiral in each pattern 28 is not particularly limited, and may be, for example, 8 to 30 turns, or 10 to 20 turns.

[0027] In this example, the pattern 28 is a curved spiral and is generally circular. However, the pattern 28 may be formed in an oval shape (e.g., an ellipse or egg shape) as a whole. The spiral is not limited to a curve, and may be a broken line shape in which a straight line is bent, or may be formed in a polygonal shape such as a square, pentagon, or hexagon as a whole.

[0028] As shown in Figs. 3 to 5, the pattern 28 is formed by alternately providing convex streaks 32 that are raised relative to a reference surface 30 of the pattern forming region 18 and concave streaks 34 that are depressed relative to the reference surface 30 along a spiral while gradually changing the height and depth relative to the reference surface 30. That is, the convex streaks 32 and the concave streaks 34 are alternately connected in the extension direction ED of the spiral, which is a line that extends so as to turn around a center point 38, thereby forming the pattern 28. The spiral is formed so as to turn through a flat surface 36, and therefore a flat surface 36 of a certain width is provided between adjacent lines (convex streaks 32 or concave streaks 34) on the inside and outside. Here, the extension direction ED is the direction in which the lines that constitute the spiral turn and extend, and is also called the turning direction.

[0029] The convex ribs 32 and concave ribs 34 can be formed on the tire surface during vulcanization molding, for example, by forming concave ribs and convex ribs by machining or laser processing on a mold used during vulcanization molding of the tire.

[0030] The reference surface 30 is a surface that serves as a reference in the pattern forming region 18, and the convex streaks 32 and the concave streaks 34 are provided on the reference surface 30. The reference surface 30 may be a curved surface that follows the profile line of the tire surface in the sidewall 16 as shown in Fig. 1, or may be a curved surface or a flat surface in which the entire pattern forming region 18 is recessed from the profile line. Even if the reference surface is a curved surface, its curvature is small, so that the reference surface 30 is a flat surface in comparison with the uneven shapes of the convex streaks 32 and the concave streaks 34.

[0031] The convex ribs 32 are components that constitute one spiral line together with the concave ribs 34, and one spiral includes multiple convex ribs 32. The convex ribs 32 are raised parts that extend in a long and thin stripe shape, and are also called ridges. In this example, the convex ribs 32 are formed in a triangular cross section as shown in FIG. 5. The width W1 of the convex ribs 32 is not particularly limited, and may be, for example, 0.1 to 1 mm. Here, the width W1 of the convex ribs 32 is the maximum dimension in the width direction of the cross-sectional shape of the convex ribs 32, and is usually the width at the base part of the convex ribs 32. The maximum height H1 of the convex ribs 32 (the distance from the reference surface 30 to the top) is not particularly limited, but is preferably 0.1 to 0.8 mm, more preferably 0.1 to 0.4 mm, from the viewpoint of design and securing the amount of rubber required for the design.

[0032] The grooves 34 are components that form a single spiral line together with the protrusions 32, and a single spiral includes multiple grooves 34. The grooves 34 are elongated recesses that extend in a stripe-like shape, and are also called narrow grooves. In this example, the grooves 34 are formed in a triangular cross section. The width W2 of the grooves 34 is not particularly limited, and may be, for example, 0.1 to 1 mm. Here, the width W2 of the grooves 34 is the maximum dimension in the width direction of the cross-sectional shape of the grooves 34, and is usually the width of the opening surface of the grooves 34. The maximum depth H2 of the grooves 34 (the distance from the reference surface 30 to the bottom) is not particularly limited, but is preferably 0.1 to 0.8 mm, more preferably 0.1 to 0.4 mm, from the viewpoint of design.

[0033] The width W1 of the ridges 32 and the width W2 of the grooves 34 may be the same or different. From the viewpoint of equalizing the amount of rubber, the width W1 is preferably 0.6 to 1.5 times the width W2, and more preferably 0.8 to 1.2 times. The maximum height H1 of the ridges 32 and the maximum depth H2 of the grooves 34 may be the same or different. From the viewpoint of equalizing the amount of rubber, the maximum height H1 is preferably 0.6 to 1.2 times the maximum depth H2, and more preferably 0.8 to 1.0 times. The volumes of the ridges 32 and the grooves 34 are not particularly limited, but the volume of the grooves 34 is preferably 0.8 to 1.2 times the volume of the ridges 32, and more preferably 0.9 to 1.1 times.

[0034] The flat surface 36 is a surface along the reference surface 30, that is, a flat surface that coincides with the reference surface 30. The flat surface 36 is an elongated strip-like surface that extends in a spiral shape around the center point 38, since it is interposed between the spiral lines consisting of the convex streaks 32 and the concave streaks 34. The width W3 of the flat surface 36 is not particularly limited, and is preferably 0.1 to 2 mm, for example, and more preferably 0.2 to 1.0 mm. The width W3 of the flat surface 36 may be set smaller than the sum of the maximum height H1 of the convex streaks 32 and the maximum depth H2 of the concave streaks 34, in which case the light attenuation effect is enhanced and the surface can be made to look darker. The width W3 of the flat surface 36 may be set larger than the sum of the maximum height H1 of the convex streaks 32 and the maximum depth H2 of the concave streaks 34, in which case the surface that reflects light in the tire axial direction AD increases, so that the number of areas that look bright increases, and the dark areas look thinner, so that the dark lines can be more clearly expressed.

[0035] As shown in Fig. 4, the height and depth of the spiral pattern 28 relative to the reference surface 30 gradually change in the extension direction ED. In detail, the height of the protruding ribs 32 that protrude relative to the reference surface 30 gradually decreases to form the recessed ribs 34 that are recessed relative to the reference surface 30. The depth of the recessed ribs 34 gradually increases to a maximum depth H2, and then the depth gradually decreases to form the protruding ribs 32 that protrude relative to the reference surface 30. The height of the protruding ribs 32 gradually increases to a maximum height H1. By repeating such changes, the protruding ribs 32 and the recessed ribs 34 are alternately provided.

[0036] 4, the cross-sectional shape of the pattern 28 along the spiral is a curved line shape that corresponds to a sine wave. However, the cross-sectional shape is not limited to a curved line shape, and may be a broken line shape that is inclined linearly.

[0037] In the first embodiment, switching positions 40 between the convex ribs 32 and the concave ribs 34 exist at regular intervals of the spiral length P1, as shown in Figures 3 and 4. Here, the switching positions 40 are boundaries between the convex ribs 32 and the concave ribs 34. In Figure 3, the switching positions 40 are indicated by dashed lines intersecting the spiral, and in this example, there are 36 switching positions 40. The regular spiral length P1 refers to a regular length as the length of the spiral streaks that make up the pattern 28 (the length in the extension direction ED).

[0038] As shown in Fig. 3 and Fig. 4, the spiral pattern 28 starts as a convex streak 32 from a starting point 42 near the center point 38, and its height gradually increases, and after reaching a maximum height H1, the height gradually decreases, passing through a switching position 40 coinciding with the reference surface 30 to become a concave streak 34. The depth of the concave streak 34 gradually increases, and after reaching a maximum depth H2, the depth gradually decreases, passing through a switching position 40 coinciding with the reference surface 30 to become a convex streak 32. In this example, the interval between the switching positions 40 is a constant length P1. The length P1 is not particularly limited, and may be set to, for example, 10 to 60 times the sum (H1+H2) of the maximum height H1 and the maximum depth H2.

[0039] In one embodiment, the dimensions of the patterns 28 may be set as follows: height HA of the pattern forming area 18 = 25 mm, width W1 of the convex stripes 32 = 0.2 mm, maximum height H1 = 0.4 mm, width W2 of the concave stripes 34 = 0.2 mm, maximum depth H2 = 0.4 mm, width W3 of the flat surface 36 = 1.2 mm, number of spiral turns in each pattern 28 = 14.

[0040] According to the first embodiment, the pattern 28 is configured to include not only the convex streaks 32 but also the convex streaks 32 and the concave streaks 34. Therefore, the amount of rubber can be equalized between the portions where the pattern 28 is not provided. In detail, the amount of rubber required to provide the convex streaks 32 can be compensated for by the portions where the concave streaks 34 are provided, so that the amount of rubber is equalized in the tire circumferential direction CD. In addition, the pattern 28 is spirally shaped, and the convex streaks 32 and the concave streaks 34 are provided alternately while gradually changing the height and depth relative to the reference surface 30, so that the change in the amount of rubber can be reduced even within the pattern 28. As described above, the occurrence of bare spots (underfill) can be suppressed during vulcanization molding of the pneumatic tire 10.

[0041] In addition, since the switching position 40 between the convex ribs 32 and the concave ribs 34 is at a constant length P1, the lengths of the convex ribs 32 and the concave ribs 34 are equalized, which also makes it possible to further equalize the amount of rubber.

[0042] Moreover, the pattern 28 is formed in a shape that spirals through the flat surface 36, and the convex ribs 32 and concave ribs 34 are alternately connected while gradually changing the height and depth. This increases the surface that reflects light, and the reflecting surface can be changed in various ways in the extending direction ED of the spiral. This enhances the light attenuation effect, and the pattern 28 can be made to look darker in appearance. This can further increase the contrast between the part where the pattern 28 is not provided and looks bright in appearance (for example, the space between the patterns 28 and the flat area 22) and the pattern 28 that looks dark.

[0043] As shown in FIG. 2, in the first embodiment, a band-like region 44 is provided on the outer side of the pattern forming region 18 in the tire radial direction RD, in which a plurality of ridges 46 extending in the tire radial direction RD are equally spaced in the tire circumferential direction CD. In one embodiment, the plurality of ridges 46 are equally spaced at intervals of 0.3 to 1.0 mm in the tire circumferential direction CD. The band-like region 44 may be provided in a part of the tire circumferential direction CD, but in this example, it is provided over the entire circumference in the tire circumferential direction CD. Therefore, the band-like region 44 is formed in an annular shape adjacent to the outer side of the decorative region 24 and surrounding it over the entire circumference. The dimension HC of the band-like region 44 in the tire radial direction RD (see FIG. 1) is preferably 5 to 12 mm.

[0044] Providing such a band-like region 44 can suppress unevenness and bareness at the interface between the members of the tread 12 and the sidewall 16. In addition, the black band-like region 44 is formed by the light attenuation effect caused by providing the protrusions 46, making the pattern formation region 18 stand out.

[0045] [Second embodiment] 6 is a plan view of a pattern 28A in a pneumatic tire according to the second embodiment. The second embodiment differs from the first embodiment in the setting of a transition position 40 between the convex stripes 32 and the concave stripes .

[0046] In the second embodiment, the switching positions 40 between the ridges 32 and the recesses 34 are set at constant angles θA around the spiral center point 38. Fig. 6 shows an example in which the angle θA is set to 360°, and the switching positions 40 are indicated by dashed lines.

[0047] In detail, the spiral pattern 28A starts as a convex stripe 32 from a starting point 42 near the center point 38, and the height gradually decreases until it turns about 45° clockwise, reaching a switching position 40 and becoming a concave stripe 34. The depth of the concave stripe 34 gradually increases, and when it turns 180°, it reaches a maximum depth H2, and then the depth gradually decreases, and when it turns another 180° (a total of 360°), it reaches the switching position 40 and becomes a convex stripe 32. The height of the convex stripe 32 gradually increases, and when it turns 180°, it reaches a maximum height H1, and then the height gradually decreases, and when it turns another 180° (a total of 360°), it reaches the switching position 40. By repeating this, the spiral pattern 28A is formed.

[0048] When the switching positions 40 are provided at intervals of a constant angle θA in this manner, the angle θA is not particularly limited, but is preferably 30° to 360°, and more preferably 60° to 360°.

[0049] In the example shown in Fig. 6, the convex streaks 32 and the concave streaks 34 are adjacent to each other through the flat surface 36 over the entire extension direction ED of the spiral. This enhances the light attenuation effect, making the pattern 28 look darker and increasing the contrast. In order to achieve such a configuration in which the convex streaks 32 and the concave streaks 34 are adjacent to each other over the entire circumference of the extension direction ED of the spiral, the angle θA is set so that 360° / θA is an odd number.

[0050] The other configurations and effects of the second embodiment are similar to those of the first embodiment, and therefore a description thereof will be omitted.

[0051] [Third embodiment] 7 is a plan view of a pattern 28B in a pneumatic tire according to the third embodiment. The third embodiment differs from the first embodiment in the setting of a transition position 40 between the convex stripes 32 and the concave stripes .

[0052] In the third embodiment, the transition position 40 between the ridges 32 and the recesses 34 is set according to an angle around the center point 38 of the spiral, and the angle on the central side of the spiral is set larger than the angle on the outer side of the spiral. In Figure 7, the transition position 40 is indicated by a dashed line.

[0053] 7, the angles are set at four stages from the inside of the spiral: θ1=360°, θ2=120°, θ3=72°, and θ4=40°. In detail, from the start point 42 near the center point 38 until it turns four times, switching positions 40 are provided every 360°, from there until it turns five times, switching positions 40 are provided every 120°, from there until it turns three times, switching positions 40 are provided every 72°, and from there until it turns two times and reaches the terminal end, switching positions 40 are provided every 40°.

[0054] In the spiral pattern 28B, even at the same angle, the length of the streaks is smaller toward the center of the spiral and larger toward the outside of the spiral. Therefore, by setting the angle at which the switching position 40 is provided to be smaller toward the outside of the spiral, the lengths of the ridges 32 and grooves 34 can be made equal between the center and outside of the spiral.

[0055] In the example shown in Fig. 7, the angles θ1 to θ4 are all set so that 360° / θX (where θX: θ1 to θ4) is an odd number. Therefore, the convex ribs 32 and the concave ribs 34 are adjacent to each other via the flat surface 36 over the entire extension direction ED of the spiral. This further enhances the light attenuation effect, making the pattern 28 appear darker and increasing the contrast.

[0056] When the angle at the center of the spiral is set to be larger than the angle at the outside of the spiral, the angle may be set for each of several turns so as to increase stepwise, or the angle may be set so as to increase gradually from the center to the outside. The other configurations and effects of the third embodiment are similar to those of the first embodiment, and therefore description thereof will be omitted.

[0057] [Other embodiments] In the above embodiment, the ridges 32 and the grooves 34 have a triangular cross section, but the cross-sectional shapes of the ridges 32 and the grooves 34 are not limited to this, and various cross-sectional shapes can be adopted.

[0058] 8 is a cross-sectional view showing a cross-sectional shape according to a first modified example. In the first modified example, the ridges 32 and the grooves 34 have a semicircular cross-section. In this case, the radius of curvature RA of the semicircle is not particularly limited and may be, for example, 0.1 to 0.5 mm.

[0059] 9 is a cross-sectional view showing a cross-sectional shape according to the second modified example. In the second modified example, the ridges 32 and the recesses 34 have a cross-sectional shape in which a semicircle is raised by a rectangle. In this case, the radius of curvature RA of the semicircle is not particularly limited, and may be, for example, 0.1 mm or more and 0.5 times or less of W1 or 0.5 times or less of W2. In addition, the amount of raising by the rectangle H3 is preferably a value obtained by subtracting the radius of curvature RA from the maximum height H1 of the ridges 32 or the maximum depth H2 of the recesses 34.

[0060] 10 is a cross-sectional view showing a cross-sectional shape according to a third modified example. In the third modified example, the ridges 32 and the grooves 34 have a trapezoidal cross section, and an isosceles trapezoid is shown as an example. In this case, the dimension W4 of the base of the trapezoid corresponding to the top surface of the ridges 32 and the bottom surface of the grooves 34 is preferably 0.2 to 0.5 times the width W1 of the ridges 32 and the width W2 of the grooves 34, respectively.

[0061] 11 is a cross-sectional view showing a cross-sectional shape according to the fourth modified example. In the fourth modified example, the ridges 32 and the grooves 34 have a cross-sectional shape in which the apex of a triangle is rounded by a circular arc. In this case, the radius of curvature RB of the circular arc is not particularly limited, and may be, for example, 0.1 mm or more and 0.5 times W1 or less or 0.5 times W2 or less.

[0062] 12 is a cross-sectional view showing a cross-sectional shape according to the fifth modified example. In the fifth modified example, the ridges 32 and the grooves 34 have a rectangular cross-sectional shape.

[0063] In these modified examples of Figs. 8 to 12, the width W1 and maximum height H1 of the ridges 32 and the width W2 and maximum depth H2 of the recesses 34 are similar to those in the first embodiment.

[0064] In the above embodiment, the pattern forming area 18 is provided separately from the mark area 20, but the mark 26 may be provided within the pattern forming area 18. That is, for example, a spiral pattern 28 may be provided in the pattern forming area 18, and the mark 26 having a flat surface may be incorporated into the pattern 28.

[0065] The type of pneumatic tire according to the present embodiment is not particularly limited, and the tire can be used for various types of tires, such as tires for passenger cars and tires for heavy loads such as trucks and buses.

[0066] In this specification, the above dimensions are those in a normal unloaded state with the pneumatic tire mounted on a normal rim and inflated to the normal internal pressure. The normal rim is the "standard rim" in the JATMA standard, and the "Measuring Rim" in the TRA and ETRTO standards. The normal internal pressure is the "maximum air pressure" in the JATMA standard, the "maximum value" described in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or the "INFLATION PRESSURE" in the ETRTO standard. However, for passenger car tires, the normal pressure is 180 kPa, but for tires marked as Extra Load or Reinforced, the normal pressure is 220 kPa.

[0067] In addition, the various numerical ranges described in the specification can be arbitrarily combined with their upper and lower limits, and all such combinations are considered to be preferred numerical ranges described in the specification. In addition, a numerical range described as "X to Y" means from X to Y.

[0068] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0069] 10...pneumatic tire, 16...sidewall, 18...pattern forming area, 28, 28A, 28B...pattern, 30...reference surface, 32...ridges, 34...grooves, 38...center point, 40...switching position

Claims

1. A spiral pattern is provided in a pattern forming area provided on the surface of the sidewall, The spiral pattern is formed by alternately providing convex ridges that are raised relative to a reference surface of the pattern forming area and concave ridges that are recessed relative to the reference surface along a spiral while gradually changing their height and depth relative to the reference surface.

2. The pneumatic tire according to claim 1 , wherein a transition point between the convex streak and the concave streak exists at every constant length of the spiral.

3. The pneumatic tire according to claim 1 , wherein transition positions between the convex streaks and the concave streaks are present at regular angular intervals around a center point of the spiral.

4. 2. The pneumatic tire according to claim 1, wherein a transition position between the convex streak and the concave streak is set according to an angle about a center point of the spiral, the angle being larger on the central side of the spiral than on the outer side of the spiral.

5. The pneumatic tire according to any one of claims 1 to 4, wherein the pattern is a curved spiral.

6. The pneumatic tire according to any one of claims 1 to 5, wherein a region in which a plurality of ridges extending in the tire radial direction are arranged at equal intervals in the tire circumferential direction is provided on the radially outer side of the pattern formation region, the region having a dimension in the tire radial direction of 5 mm or more and 12 mm or less.

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