AU2015319188A1

AU2015319188A1 - Pneumatic tire

Info

Publication number: AU2015319188A1
Application number: AU2015319188A
Authority: AU
Inventors: Takuya Inoue
Original assignee: Yokohama Rubber Co Ltd
Current assignee: Yokohama Rubber Co Ltd
Priority date: 2014-09-17
Filing date: 2015-09-15
Publication date: 2017-05-04
Anticipated expiration: 2035-09-15
Also published as: DE112015004233T5; AU2015319188B2; JP6617560B2; AU2015319188B9; CN107074041A; WO2016043191A1; JPWO2016043191A1; CN107074041B

Abstract

A region that is on the side wall surface of this pneumatic tire and includes the maximum width position of the pneumatic tire is provided with a decoration area having a side pattern. This decoration area includes: a ridge region provided with a plurality of ridges extending in one direction; and a plurality of stripe regions extending like stripes. Each of the stripe regions is provided with: a first stripe-shaped smooth surface, the periphery of which is surrounded by the ridge region; and a plurality of first dimple-shaped recessed portions that are surrounded by the first smooth surface and are recessed relative to the first smooth surface. The first smooth surfaces extend so as to incline from the radial direction of the tire to the circumferential direction of the tire. The stripe regions are each arranged and scattered in the circumferential direction of the tire. The first dimple-shaped recessed portions are aligned along the direction in which the stripe region extends like a strip.

Description

PNEUMATIC TIRE

Technical Field [0001]

The present invention relates to a pneumatic tire, and particularly relates to a pattern on a sidewall surface of a pneumatic tire.

Background Art [0002]

In recent years, reduction in rolling resistance of a pneumatic tire has been sought in order to improve the fuel economy of a vehicle on which the pneumatic tire is mounted and to improve the maximum speed of the vehicle. In order to reduce the rolling resistance of the pneumatic tire, various configurations in which the construction of the pneumatic tire, the tread pattern design, and the like are changed have been proposed.

Also, in order to improve the fuel economy of the vehicle and to improve the maximum speed of the vehicle, reducing the air resistance of the pneumatic tire during rolling motion has been proposed. The air resistance of the pneumatic tire is affected by recesses and protrusions of a tread pattern provided on a tread portion surface and by recesses and protrusions in markings and a pattern provided on a sidewall surface.

[0003]

For example, a pneumatic tire is known that includes a plurality of dimple-like recessed portions provided in a first region including a maximum tire width position of a sidewall surface, and a plurality of linear trough portions formed by a serration process extending in one direction around the recessed portions to enclose the recessed portions (Patent Document 1).

Citation List Patent Literature [0004]

Patent Document 1: Japanese Unexamined Patent Application Publication No. 2012-106583A

Summary of Invention Technical Problem [0005] 1

The aforementioned pneumatic tire provided with the dimple-like recessed portions provided on the sidewall surface can reduce air resistance and improve fuel economy. Unfortunately, the recessed portions are provided uniformly in a decorative region of the sidewall surface, and the total number of the recessed portions is thus significantly large. For these recessed portions, a mold for tire vulcanization is required to have a large number of protrusions. This causes a problem of an increase in process cost of the mold for tire vulcanization and thus a problem of an increase in manufacturing cost of the tire.

[0006]

An object of the present invention is to provide a pneumatic tire that can reduce process cost of a mold for tire vulcanization, thus reducing manufacturing cost of the tire, and can effectively reduce air resistance during tire rolling motion.

Solution to Problem [0007]

The present technology includes various embodiments of a pneumatic tire described below.

Embodiment 1 A pneumatic tire includes a tread portion and a side portion. The side portion has a sidewall surface provided with a decorative region having a side pattern, the decorative region being disposed in a region including a maximum tire width position of the pneumatic tire. The decorative region includes: a ridge region provided with a plurality of ridges extending in one direction; and a plurality of band regions each including a band-shaped first smooth surface not having ridges and having a periphery surrounded by the ridge region, and a plurality of dimple-shaped first recessed portions surrounded by the first smooth surface and recessed relative to the first smooth surface, the first smooth surface extending in the band shape on the sidewall surface from inward to outward in a tire radial direction, and the first smooth surface extending so as to incline from the tire radial direction to a tire circumferential direction upon extending outward in the tire radial direction. The band regions are disposed at intervals in the tire circumferential direction on the sidewall surface. The first recessed portions are aligned in a direction of extension of the band regions in the band shape.

[0008]

Embodiment 2 2

In the pneumatic tire according to Embodiment 1, a plurality of pairs of band regions adjacent to each other in the tire circumferential direction among the band regions are disposed at intervals in the tire circumferential direction, and the band regions in each of the pairs are positioned closer to each other than to another band regions.

[0009]

Embodiment 3

In the pneumatic tire according to Embodiment 2, rows of the first recessed portions included in the two band regions adjacent to each other in the tire circumferential direction in each of the pairs occupy regions partially overlapping on a tire circumference in the tire circumferential direction.

[0010]

Embodiment 4

In the pneumatic tire according to any one of Embodiments 1 to 3, at least one of: a radially inner end portion of the first smooth surface of each of the band regions and a radially outward end portion of the first smooth surface of each of the band regions has a tip tapered down in the tire circumferential direction.

[0011]

Embodiment 5

In the pneumatic tire according to any one of Embodiments 1 to 4, the band regions incline in a same direction with respect to the tire circumferential direction and are arranged so as to form a swirl shape around a tire rotational axis.

[0012]

Embodiment 6

In the pneumatic tire according to any one of Embodiments 1 to 5, an extending direction of the ridges in the ridge region and an extending direction of the first smooth surfaces are opposite to each other in the tire circumferential direction upon viewing the extending directions from inward to outward in the tire radial direction.

[0013]

Embodiment 7

In the pneumatic tire according to any one of Embodiments 1 to 6, the sidewall surface is provided with a marking display region displaying a marking, in addition to the decorative region; the marking display region includes a second smooth surface surrounding the marking and not having ridges, and a plurality of dimple-shaped second recessed portions surrounded by the second 3 smooth surface and recessed relative to the second flat surface; and the second recessed portions are aligned, and rows of the second recessed portions extend from inward to outward in the tire radial direction and incline from the tire radial direction to the tire circumferential direction.

[0014]

Embodiment 8

In the pneumatic tire according to Embodiment 7, the band regions incline in a same direction with respect to the tire circumferential direction and are arranged so as to form a swirl shape around a tire rotational axis, and the second recessed portions are aligned in a swirling direction of the swirl shape.

[0015]

Embodiment 9

In the pneumatic tire according to any one of Embodiments 1 to 8, the first smooth surfaces protrude further outward on the sidewall surface than peaks of the ridges in the ridge region.

Advantageous Effects of Invention [0016]

The aforementioned pneumatic tire can reduce process cost of a mold for tire vulcanization, thereby reducing manufacturing cost of the tire, and can effectively reduce air resistance during tire rolling motion.

Brief Description of Drawings [0017] FIG. 1 is a profile cross-sectional view of an example of a pneumatic tire according to a form of present embodiments. FIG. 2 illustrates an example of a side portion surface according to a form of present embodiments. FIG. 3A is an enlarged view of a portion of a pattern on a sidewall surface of the tire illustrated in FIG. 2. FIG. 3B is a cross-sectional view taken along the line X-X in FIG. 3A. FIG. 4 illustrates an air flow around the sidewall surface of the tire according to a form of present embodiments. FIG. 5 illustrates air resistance with the pattern on the sidewall surface of the tire according to a form of present embodiments. FIG. 6 illustrates an example of different arrangement of band regions used for the tire according to a form of present embodiments. 4

Description of Embodiments [0018]

The details of a pneumatic tire according to the present embodiments (hereinafter, simply referred to as a tire) are described below.

The below-described pneumatic tire according to a form of the present embodiments is, for example, applied to a tire for a passenger vehicle, and may also be applied to a tire for a small truck, or as a tire for a bus and a truck. The pneumatic tire according to a form of the present embodiments that will be described below is a tire for a passenger car.

[0019]

In the following description, "tire width direction" is the direction parallel to a rotational axis of the pneumatic tire. "Outward in the tire width direction" is the direction away from a tire center line CL representing the tire equatorial plane in the tire width direction. Also, "inward in the tire width direction" is the direction toward the tire center line CL in the tire width direction. "Tire circumferential direction" is the direction of rotation of the pneumatic tire with the rotational axis of the pneumatic tire as a center of rotation. "Tire radial direction" is the direction orthogonal to the rotational axis of the pneumatic tire. "Outward in the tire radial direction" is the direction away from the rotational axis. "Inward in the tire radial direction" is a direction toward the rotational axis.

[0020]

Tire Structure FIG. 1 is a profile cross-sectional view of an example of a tire 10 according to a form of the present embodiments. The tire 10 includes a tread portion 10T having a tread pattern, a pair of bead portions 10B, and a pair of side portions 10S provided on both sides of the tread portion 10T, connecting the pair of bead portions 10B to the tread portion 10T.

The tire 10 mainly includes, as framework components, a carcass ply layer 12, a belt layer 14, and bead cores 16, and, around these framework components, a tread rubber member 18, side rubber members 20, bead filler rubber members 22, a rim cushion rubber member 24, and an innerliner rubber member 26.

[0021]

The carcass ply layer 12 is constituted of a carcass ply member that is formed of organic fibers covered with rubber and that is wound between the pair of annular bead cores 16 so as to be formed into a toroidal shape. The carcass ply material is wound back at the bead cores 16 so to extend outward in 5 the tire radial direction. The belt layer 14 constituted of two belt members 14a, 14b is disposed outward of the carcass ply layer 12 in the tire radial direction. The belt layer 14 members are constituted of rubber-covered steel cords. The steel cords are arranged inclined at a predetermined angle of, for example, from 20 to 30 degrees with respect to the tire circumferential direction. A width in the tire width direction of the lower layer belt member 14a is greater than that of the upper layer belt member 14b. The steel cords of the two belt members 14a, 14b are inclined in opposite directions. As such, the belt members 14a and 14b are crossing layers serving to suppress expansion of the carcass ply layer 12 due to the pressure of the air in the tire 10.

[0022]

The tread rubber member 18 is disposed outward of the belt layer 14 in the tire radial direction. Both end portions of the tread rubber member 18 connect to the side rubber members 20 to form the side portions 10S. The rim cushion rubber members 24 are disposed at the radially-inner ends of the side rubber members 20, and come into contact with a rim on which the tire 10 is mounted. The bead filler rubber members 22 are disposed outward of the bead cores 16 in the tire radial direction so as to be held between the portions of the carcass ply layer 12 that is not wound back at the bead cores 16 and the portions of the carcass ply layer 12 that are wound back at the bead cores 16. The innerliner rubber member 26 is disposed on an inner surface of the tire 10 facing a tire cavity region that is filled with air and is surrounded by the tire 10 and the rim.

In addition, the tire 10 includes a two-layer belt cover layer 30 that is formed of organic fiber or steel cords covered with rubber and covers the belt layer 14 from the outer side in the tire radial direction of the belt layer 14. Also, the tire 10 may include bead stiffeners between the carcass layer 12 wound back at the bead cores 16 and the bead filler rubber members 22. The tire according to a form of the present embodiments has the above-described structure. However, the tire structure is not particularly limited, and a known tire structure may be applied. No particular limitation is intended to the tread pattern in the tread portion 10T of the tire 10 of a form of the present embodiments.

[0023]

Sidewall Pattern FIG. 2 illustrates an example of a sidewall surface of the side portion 10S. FIG. 3 A is an enlarged view of a portion of the pattern on the sidewall surface of the side portion 10S of the tire illustrated in FIG. 2. FIG. 3B is a cross-sectional view taken along the line X-X in FIG. 3A. 6

An information display region 32, a marking display region 33, and a decorative region 34 are provided on the sidewall surface of the tire according to a form of the present embodiments. The marking combination of the alphanumeric character "Y" and the alphanumeric characters "YOKOHAMA" in FIG. 2 is a trade name.

Information, such as the tire size and standards of the tire 10, is written in the information display region 32. A marking, such as the brand name or manufacturer of the tire 10, is displayed in the marking display region 33.

[0024]

The decorative region 34 is disposed in a region including the maximum tire width position of the tire 10. The pattern described below is provided in the decorative region 34 and is a side pattern of the side portion 10S. The decorative region 34 includes a ridge region 36 and band regions 38. A plurality of ridges 36a extending in one direction are disposed in the ridge region 36. For example, a serration process is applied to the inner surface of a mold for vulcanizing the tire 10, so that ridge-shaped recesses and protrusions that correspond to the ridge region 36 are formed on the inner surface of the mold. The recesses and protrusions are transferred onto the sidewall surface of the tire in vulcanization, thereby forming the ridges 36a. (In FIG. 2, the lines of the ridges 36a in the ridge region 36 are unclear and thus unrecognizable.) [0025] A plurality of the band regions 38 are provided on the sidewall surface. Each of the band regions 38 includes a first band-shaped smooth surface 39, the periphery of which is surrounded by the ridge region 36, and first recessed portions 40. A plurality of the first recessed portions 40 are provided and shaped as circular dimples. The circular shape of the first recessed portions 40 is perfectly circular or elliptical. As illustrated in FIG. 3B, the first recessed portions 40 are surrounded by the first smooth surface 39 and recessed relative to the first smooth surface 39 inward in the tire width direction (toward the tire cavity region side). As illustrated in FIGS. 2, 3A, the first smooth surface 39 extends in a band shape on the sidewall surface from inward to outward in the tire radial direction and extends so as to incline from the tire radial direction to the tire circumferential direction when extending outward in the tire radial direction.

The band regions 38 are disposed at intervals in the tire circumferential direction on the sidewall surface. The dimple-shaped first recessed portions 40 are aligned, and the row of the first recessed portions 40 extends in the direction 7 in which the band region 38 extends in a band shape. The first recessed portions 40 in a form of the present embodiments are preferably aligned in one row. However, the number of the rows is not limited to one and may be two or greater.

[0026]

This pattern in the decorative region 34 can efficiently reduce air resistance during tire rolling motion even with the dimple-shaped first recessed portions 40 being fewer in number than in conventional tires. Accordingly, process cost of the mold for tire vulcanization can be reduced, thereby reducing manufacturing cost of the tire, and air resistance during tire rolling motion can be efficiently reduced.

[0027] FIG. 4 illustrates an air flow around the sidewall surface of the tire 10.

When the tire 10 assembled on a rim R travels in the direction of the arrow F, a speed difference is caused between an air flow slightly remote from the sidewall surface and an air flow in the vicinity of the sidewall surface. This speed difference increases as the travel speed of the tire increases. If the difference exceeds a certain limit, the air flow A around the sidewall surface swirls and separates. This separation phenomenon significantly increases air resistance of the sidewall. To make the separation phenomenon less likely to be produced, that is, to cause the separation phenomenon to be produced on the downstream side, the row of the first recessed portions 40 extending outward in the tire radial direction conforms to the direction the band region 38 extends so as to incline from the tire radial direction to the tire circumferential direction. This configuration causes the separation phenomenon to be produced on the downstream side with respect to the advancement direction to the utmost in the rotating and traveling tire, in a similar manner to dimple-shaped recessed portions provided uniformly in the decorative region of the sidewall surface. This configuration can thus cause the swirling flow to be produced on the downstream side, thereby reducing air resistance.

Since the first recessed portions 40 in a form of the present embodiments are disposed in the band region 38, the number of the first recessed portions 40 is smaller than the total numbers of dimple-shaped recessed portions provided uniformly in the decorative regions of conventional tires. This can reduce process cost required to produce protrusions, corresponding to the recessed portions, of the mold for tire vulcanization. Accordingly, manufacturing cost of the tire can be reduced. The tire according to a form of the present embodiments 8 can thus reduce manufacturing cost of the tire and can effectively reduce air resistance during tire rolling motion.

[0028]

The band region 38 of the tire 10 according to a form of the present embodiments may be separated with regular distances therebetween on the tire circumference so as to be disposed at regular intervals but preferably has the configuration described below. That is, concerning the band regions, a plurality of pairs of the band regions adjacent to each other in the tire circumferential direction are disposed at intervals in the tire circumferential direction. At this time, the band regions in each of the pairs are positioned closer to each other than to the other band regions. This configuration allows the rows of the first recessed portions 40 to be paired in plurality in correspondence with the pairs of the adjacent band regions. These row pairs can cause the separation phenomenon of the air flow around the sidewall surface due to the motion of the tire to be efficiently produced on the downstream side as described above.

[0029]

When the band regions 38 are paired, the rows of the first recessed portions 40 included in the two band regions adjacent to each other in the tire circumferential direction in each of the pairs preferably occupy regions that partially overlap on the tire circumference, in the tire circumferential direction. The first recessed portions 40 are provided on the tire circumference without discontinuity in the pair of the band regions 38, so that the air flow around the sidewall surface comes into contact with the rows of the first recessed portions 40 in the band regions 38 during tire rolling motion, thus causing the separation phenomenon to be more efficiently produced on the downstream side.

[0030]

In a form of the present embodiments, at least one of: the radially inner end portion of the first smooth surface 39 of each of the band regions 38 (an end portion in the direction inclining from the tire radial direction to the tire circumferential direction) and the radially outer end portion of the first smooth surface 39 of the band region 38 (an end portion in the direction inclining from the tire radial direction to the tire circumferential direction) preferably has a tip tapered down in the tire circumferential direction. Here, as illustrated in FIG. 5, the air flows in directions of the straight arrows during tire rolling motion (rotation in the direction Ri in FIG. 5) when viewed with reference to the first smooth surfaces 39. Since the end portions of the first smooth surfaces 39 have the tips tapered down in the tire circumferential direction, this air flow can be adjusted to thereby reduce air resistance. Especially, if both radially inner and 9 outer end portions on the first smooth surfaces 39 of the band regions 38 have the tips tapered down in the tire circumferential direction, the air flow can be adjusted to thereby reduce air resistance, even with the tire fitted in the opposite direction to rotate in the direction R2 in FIG. 5. FIG. 5 illustrates air resistance with the pattern on the sidewall surface of the tire according to a form of the present embodiments. The marking combination of the alphanumeric character "Y" and the alphanumeric characters "YOKOHAMA" in FIG. 5 is a trade name.

The tip tapered down in the tire circumferential direction includes an acute tip and a tip having a corner rounded with a radius of curvature of 2.0 mm or less.

[0031]

It is preferable that the band regions 38 in a form of the present embodiments incline in the same direction from the tire radial direction to the tire circumferential direction and that the band regions 38 are arranged so as to form a swirl shape around the tire rotational axis, in order to adjust the air flow. However, as long as the separation phenomenon of the air flow around the sidewall surface, illustrated in FIG. 4, due to the motion of the tire 10 can be produced on the downstream side, the band regions 38 may incline in different directions with respect to the tire circumferential direction as illustrated in FIG. 6. FIG. 6 illustrates an example of different arrangement of the band regions 38. In this case, the first recessed portions 40 included in the chevron-shaped band regions 38 illustrated in FIG. 6 also preferably occupy regions that partially overlap on the tire circumference, in the tire circumferential direction, which is not illustrated in FIG. 6, in order to more efficiently produce the separation phenomenon on the downstream side.

[0032]

The extending direction of the ridges 36a in the ridge region 36 and the extending direction of the first smooth surfaces 39 are preferably opposite to each other in the tire circumferential direction (the clockwise direction and the counterclockwise direction) when viewed from inward to outward in the tire radial direction, in order to make the first smooth surfaces 39 conspicuous. With the first smooth surfaces 39 conspicuous in the decorative region 34, a person who views the sidewall surface moves the eyes in the inclining direction of the first smooth surfaces 39, thereby readily recognizing a marking in the marking display region 33. Moreover, the swirl shape of the first smooth surfaces 39 and the rows of the first recessed portions 40 surrounded by the first smooth surfaces 39 is conspicuous, so that the tire can be readily recognized as a tire that can adjust the air flow and reduce air resistance. 10 [0033]

In a form of the present embodiments, as illustrated in FIG. 2, the marking display region 33 preferably includes a second smooth surface 42 that surrounds the marking and does not include ridges and a plurality of dimple-shaped second recessed portions 44 that are surrounded by the second smooth surface 42 and recessed relative to the second smooth surface 42. Preferably, the second recessed portions 44 are aligned, and the rows of the second recessed portions 44 extend from inward to outward in the tire radial direction and incline from the tire radial direction to the tire circumferential direction. Specifically, the rows of the second recessed portions 44 preferably face in the same direction with respect to the tire circumferential direction as the direction in which the rows of the first recessed portions 40 face with respect to the tire circumferential direction. In other words, the second recessed portions 44 are preferably aligned in the swirling direction of the band regions 38 and the first recessed portions 40 extending in a swirl shape. In the marking display region 33, the marking is disposed on the second smooth surface 42 to allow the marking to be readily recognized. However, the second smooth surface 42 readily causes the aforementioned separation phenomenon of the air flow. Thus, the dimple-shaped second recessed portions 44 are preferably arranged so as to be aligned in the marking display region 33. Here, in order to allow the air flow to contact the rows of the second recessed portions 44 in a longer range, the rows of the second recessed portions 44 extend from inward to outward in the tire radial direction and incline from the tire radial direction to the tire circumferential direction.

[0034]

As illustrated in FIG. 3B, the first smooth surfaces 39 in a form of the present embodiments preferably protrude further outward on the sidewall surface than the peaks of the ridges 36a in the ridge region 36, in order to reduce resistance of the air flow that is readily produced by the recesses and protrusions of the ridges 36a. This configuration efficiently enables the function of the first recessed portions 40 surrounded by the first smooth surface 39, that is, efficiently causes the separation phenomenon of the air flow to be produced on the downstream side.

[0035]

The decorative region 34 of the tire 10 may be disposed on each of the sidewall surfaces on both side in the tire width direction or may be disposed on only one of the sidewall surfaces. If the decorative regions 34 are disposed on both sidewall surfaces, the band regions 38 on both sidewall surfaces preferably 11 extend in the same direction with respect to the tire circumferential direction. The band regions 38 of the tire 10 fitted to a wheel on one side of a vehicle, for example, to a left wheel may extend in such a direction with respect to the tire circumferential direction as to form a swirl shape corresponding to the rotation direction when the vehicle moves forward, and on the other hand, the band regions 38 of the tire 10 fitted to a wheel on the other side of the vehicle, for example, to a right wheel may extend in such a direction with respect to the tire circumferential direction as to form a swirl shape corresponding to the rotation direction when the vehicle moves backward. In this case, the action of the first recessed portions 40 also causes the separation phenomenon of the air flow to be produced on the downstream side in the band regions 38 of the tires 10 on both sides.

The first recessed portions 40 and the second recessed portions 44 of the tire 10 each have a circular aperture shape; however, the shape is not limited thereto and may be polygonal. The first recessed portions 40 and the second recessed portions 44 are not limited to have such a shape as to be recessed in the depth direction of the recessed portions into an arc shape and may have such a shape as to be recessed into a rectangular shape.

[0036]

Examples, Comparative Example, Conventional Example

To confirm the effects of the present embodiments, various patterns were formed on the sidewall surfaces, and manufacturing cost and air resistance of the tires were checked. The tires had a size of 195/65R15 91H, the air pressure of the front and rear wheels was 240 kPa, and 15><6 J rims were used.

[0037]

Air resistance was checked by calculating fuel economy with the tires fitted to a vehicle (minivan type). Specifically, the vehicle was driven for 500 laps of a circuit track having a total length of 2 km at a speed of 100 km/hour, and the fuel economy per predetermined distance was calculated from the fuel consumption rate. A higher fuel economy indicates less air resistance.

Manufacturing cost was checked by estimating production cost of a mold. Specifically, the first recessed portions 40 and the second recessed portions 44 each had a circular aperture shape having a diameter of 3.6 mm and a depth of 0.7 mm. Manufacturing cost of a tire is affected by production cost of protrusions, corresponding to the first recessed portions 40 and the second recessed portions 44, on the inner surface of a mold.

[0038] 12

Eleven tires were prepared for Conventional Example, Comparative Example, and Examples 1 to 9.

Conventional Example included the sidewall surface illustrated in FIG. 2 without the first recessed portions 40 and the second recessed portions 44 provided.

Comparative Example included a sidewall surface having dimple-shaped recessed portions uniformly provided on the entire surface of a decorative region.

Examples 1 to 8 each included the sidewall surface illustrated in FIG. 2 with the first recessed portions 40 provided but without the second recessed portions 44 provided. Example 9 included the sidewall surface illustrated in FIG. 2 with the first recessed portions 40 and the second recessed portions 44 provided. "Inclining direction" in "Presence/absence of inclining arrangement of first recessed portion and inclining direction" in Tables 1, 2 indicates whether the direction with respect to the tire circumferential direction was the same as or opposite to the rotation direction when the tire moves forward. In Tables, "same direction as rotation direction" indicates that concerning two directions with respect to the tire circumferential direction, the rows of the first recessed portions extended in the same direction as the rotation direction when the tire moves forward with respect to the tire circumferential direction, from the first recessed portions located radially outward to the first recessed portions located radially inward. "Direction opposite to rotation direction" indicates that concerning two directions with respect to the tire circumferential direction, the rows of the first recessed portions extended in the direction opposite to the rotation direction when the tire moved forward with respect to the tire circumferential direction, from the first recessed portions located radially outward to the first recessed portions located radially inward. "Spiral" indicates that the band regions 38 and the first recessed portions 40 were arranged into a swirl shape as illustrated in FIG. 2, and "chevron-shaped" indicates that the band regions 38 and the first recessed portions 40 were arranged into a shape illustrated in FIG. 6.

In Tables 1, 2, "Present" for "Presence/absence of band region pair" indicates that adjacent two band regions 38 were paired and a plurality of the pairs were disposed at intervals on the tire circumference, and "Absent" indicates that the band regions 38 were not paired and were disposed at regular intervals on the tire circumference one by one. 13

In Tables 1, 2, "Present" for "Presence/absence of tapered-down tip of band region" indicates that the tips were at an acute angle of 10 degrees, and "Absent" indicates that the tips were rounded with a radius of curvature of 3.5 mm.

[0039]

In Tables 1, 2 below, the fuel economy and the manufacturing cost are expressed as index values with the values for Conventional Example being defined as 100. Higher index values for fuel economy indicate better fuel economy (less amount of fuel required for traveling for a certain distance) and less air resistance. Lower index values for manufacturing cost indicates higher manufacturing cost.

[0040] [Table 1]

Conventional Example Comparative Example Example 1 Example 2 Example 3 Example 4 Presence/absence and position of first recessed portion Absent Present, Uniformly on entire surface of decorative region Present, In band region Present, In band region Present, In band region Present, In band region Presence/absence of inclining arrangement of first recessed portion and inclining direction - Absent Present (spiral), Same inclining direction for all (same direction as rotation direction) Present (spiral), Same inclining direction for all (same direction as rotation direction) Present (chevron-shaped), Different inclining directions Present (spiral), Same inclining direction for all (direction opposite to rotation direction) Presence/absence of band region pair - Absent Absent Absent Absent Absent Presence/absence of tapered-down tip of band region - - Absent Present Absent Absent Fuel economy 100 104 103 104 103 103 Manufacturing 100 90 98 98 98 98 14 cost [0041] [Table 2]

Example 5 Example 6 Example 7 Example 8 Example 9 Presence/absence and position of first and second recessed portion Present(only first recessed portion), In band region Present (only first recessed portion), In band region Present(only first recessed portion), In band region Present (only first recessed portion), In band region Present (first and second recessed portion), In band region + marking display region Presence/absence of inclining arrangement of first recessed portion and inclining direction Present (spiral), Same inclining direction for all (same direction as rotation direction) Present (spiral), Same inclining direction for all (direction opposite to rotation direction) Present (spiral), Same inclining direction for all (same direction as rotation direction) Present (spiral), Same inclining direction for all (direction opposite to rotation direction) Present (spiral), Same inclining direction for all (same direction as rotation direction) Presence/absence of band region pair Present Present Present Present Present Presence/absence of tapered-down tip of band region Absent Absent Present Present Present Fuel economy 104 104 105 104 105 Manufacturing cost 98 98 98 98 97 [0042]

Table 1 shows that Examples 1 to 8 provide substantially equivalent levels of fuel economy (require substantially equivalent amounts of fuel for traveling for a certain distance) in comparison to the Comparative Example and can significantly reduce manufacturing cost. A decrease of fuel economy by one or two points is significantly small and allowable.

Manufacturing cost for Examples 1 to 9 increases in comparison to the Conventional Example (the index values are lower than that for Conventional Example); however, the degree of the increase is significantly lower than Comparative Example.

[0043] 15

The pneumatic tire of the present invention has been described in detail above. However, no limitation of the present invention to the above-described embodiments and examples is intended. Various improvements and variations are of course applicable within the scope of the present invention.

Reference Signs List [0044] 10 Pneumatic tire 10T Tread portion 10B Bead portion 10S Side portion 12 Carcass ply layer 14 Belt layer 16 Bead core 18 Tread rubber member 20 Side rubber member 22 Bead filler rubber member 24 Rim cushion rubber member 26 Innerliner rubber member 28 Bead stiffener 30 Belt cover layer 32 Information display region 33 Marking display region 34 Decorative region 36 Ridge region 38 Band region 39 First smooth surface 40 First recessed portion 42 Second smooth surface 44 Second recessed portion 16

Claims

Claims [Claim 1] A pneumatic tire comprising: a tread portion; and a side portion; the side portion having a sidewall surface provided with a decorative region having a side pattern, the decorative region being disposed in a region including a maximum tire width position of the pneumatic tire; the decorative region comprising: a ridge region provided with a plurality of ridges extending in one direction; and a plurality of band regions each comprising a band-shaped first smooth surface not having ridges and having a periphery surrounded by the ridge region, and a plurality of dimple-shaped first recessed portions surrounded by the first smooth surface and recessed relative to the first smooth surface, the first smooth surface extending in the band shape on the sidewall surface from inward to outward in a tire radial direction, and the first smooth surface extending so as to incline from the tire radial direction to a tire circumferential direction upon extending outward in the tire radial direction; the band regions being disposed at intervals in the tire circumferential direction on the sidewall surface; and the first recessed portions being aligned in a direction of extension of the band regions in the band shape. [Claim
2] The pneumatic tire according to claim 1, wherein a plurality of pairs of band regions adjacent to each other in the tire circumferential direction among the band regions are disposed at intervals in the tire circumferential direction; and the band regions in each of the pairs are positioned closer to each other than to another band regions. [Claim
3] The pneumatic tire according to claim 2, wherein rows of the first recessed portions included in the two band regions adjacent to each other in the tire circumferential direction in each of the pairs occupy regions partially overlapping on a tire circumference in the tire circumferential direction. [Claim
4] The pneumatic tire according to any one of claims 1 to 3, wherein at least one of: a radially inner end portion of the first smooth surface of each of the band regions and a radially outer end portion of the first smooth surface of each of the band regions has a tip tapered down in the tire circumferential direction. [Claim
5] The pneumatic tire according to any one of claims 1 to 4, wherein the band regions incline in a same direction with respect to the tire circumferential direction and are arranged so as to form a swirl shape around a tire rotational axis. [Claim
6] The pneumatic tire according to any one of claims 1 to 5, wherein an extending direction of the ridges in the ridge region and an extending direction of the first smooth surfaces are opposite to each other in the tire circumferential direction upon viewing the extending directions from inward to outward in the tire radial direction. [Claim
7] The pneumatic tire according to any one of claims 1 to 6, wherein the sidewall surface is provided with a marking display region displaying a marking, in addition to the decorative region; the marking display region comprises a second smooth surface surrounding the marking and not having ridges, and a plurality of dimple-shaped second recessed portions surrounded by the second smooth surface and recessed relative to the second flat surface; and the second recessed portions are aligned, and rows of the second recessed portions extend from inward to outward in the tire radial direction and incline from the tire radial direction to the tire circumferential direction. [Claim
8] The pneumatic tire according to claim 7, wherein the band regions incline in a same direction with respect to the tire circumferential direction and are arranged so as to form a swirl shape around a tire rotational axis; and the second recessed portions are aligned in a swirling direction of the swirl shape. [Claim
9] The pneumatic tire according to any one of claims 1 to 8, wherein the first smooth surfaces protrude further outward on the sidewall surface than peaks of the ridges in the ridge region.