WO2015029929A1

WO2015029929A1 - Pneumatic tire

Info

Publication number: WO2015029929A1
Application number: PCT/JP2014/072108
Authority: WO
Inventors: 武士金子
Original assignee: 横浜ゴム株式会社
Priority date: 2013-08-26
Filing date: 2014-08-25
Publication date: 2015-03-05
Also published as: JP2015042537A; JP6149607B2

Abstract

Provided is a pneumatic tire capable of reducing air resistance when the tire is rolling and capable of making unevenness caused by tire construction, etc., less conspicuous on the sidewall surface. A sidewall section has a patterned area having a n number (n being a natural number of at least 2) of recessed rows having a plurality of dimple-shaped recessed sections arranged at even intervals upon a second arc of a set radius (R₂) having as the center thereof any point (O₂) among n points provided at even intervals upon a first arc of a set radius (R₁) having the tire center of rotation (O₁) as the center thereof.

Description

Pneumatic tire

The present invention relates to a pneumatic tire, and more particularly to a design of a sidewall surface of the pneumatic tire.

In recent years, in order to improve the fuel consumption of a vehicle equipped with a pneumatic tire and improve the maximum speed of the vehicle, it is required to reduce the rolling resistance of the pneumatic tire. In order to reduce the rolling resistance of a pneumatic tire, various forms in which the structure of the pneumatic tire, the tread pattern design, and the like are changed have been proposed.
In order to improve vehicle fuel efficiency and vehicle maximum speed, it has also been proposed to reduce the air resistance of a pneumatic tire during rolling. The air resistance of the pneumatic tire is affected by the unevenness of the tread pattern provided on the surface of the tread portion and the unevenness of the mark or pattern provided on the sidewall surface.

For example, a pneumatic tire is known in which there is no spew or spew mark on the sidewall surface and the air resistance can be reduced (Patent Document 1).
A plurality of recesses are provided in a first region including the tire maximum width position on the sidewall surface of the pneumatic tire, and around each of the recesses, a plurality of extending in one direction so as to cover each of the recesses A linear trough is provided and serrated.
Providing a plurality of recesses in the region including the tire maximum width position on the sidewall surface of the pneumatic tire can reduce the air resistance caused by the rolling of the pneumatic tire, which is effective in improving fuel consumption.

JP 2012-106583 A

Incidentally, in order to achieve weight reduction and low rolling resistance of pneumatic tires, the thickness of the rubber of the sidewall (hereinafter also referred to as a side gauge) is reduced. However, when the side gauge is made thin, an appearance defect that causes irregularities on the sidewall surface occurs with a high probability. Specifically, in the molding process at the time of manufacturing the tire, the sheet-like carcass member is wound once on the tire molding drum, and the winding start end and the winding end end of the carcass member are partially overlapped and joined. For this reason, the thickness of the overlapped portion becomes thick, and this portion appears as irregularities on the sidewall surface in the final tire. In particular, in a radial tire in which one carcass member is used, this unevenness is conspicuous. This poor appearance does not adversely affect the durability and other athletic performances of the tire, but gives the user a concern that the tire may be a defective product with low durability and other athletic performance.

In the pneumatic tire described above in which a plurality of recesses are provided on the sidewall surface, by providing the plurality of recesses, the unevenness caused by the tire structure and the like as described above is less noticeable on the sidewall surface. Therefore, it is required to be more inconspicuous.

Therefore, an object of the present invention is to provide a pneumatic tire that can reduce the air resistance during rolling of the tire and make the unevenness caused by the tire structure or the like less noticeable on the sidewall surface.

One embodiment of the present invention is a pneumatic tire having a sidewall portion. The sidewall portion is any one of n points (n is a natural number of 2 or more) provided at equal intervals on a first arc having a constant radius R ₁ centered on the tire rotation center O ₁ . It has a pattern region including n recess rows each having a plurality of dimple-like recesses arranged at equal intervals on a second arc having a constant radius R ₂ centered at a point O ₂ .

The interval between the adjacent second arcs is preferably wider than the center interval between the plurality of recesses on the second arc.

It is preferable that the equivalent circle diameter of each of the plurality of recesses periodically varies according to the circumferential position on the first arc at the center of the second arc where each of the recesses is located.
Alternatively, it is preferable that the equivalent circle diameter of each of the plurality of recesses periodically varies according to the circumferential position of the second arc where each of the recesses is located.
Alternatively, it is preferable that the equivalent circle diameter of each of the plurality of recesses periodically varies according to the circumferential position of the tire.
Alternatively, it is preferable that the equivalent circle diameter of each of the plurality of recesses varies according to the radial position of the tire.

The circle equivalent diameter of the recess is preferably 1.0 to 5.0 mm. The depth of the recess is preferably 0.3 to 1.5 mm.

It is preferable that portions other than the portion where the plurality of concave portions are formed in the pattern region are provided with a plurality of linear valley portions extending in one direction and subjected to serration processing.
The ratio of the total area of the plurality of concave portions to the area of the serrated portion is preferably 25% to 60%.

The pattern region is preferably provided in a region having a distance of 30% to 80% of the tire cross-section height in the tire radial direction from the innermost end portion in the tire radial direction of the sidewall portion.

The sidewall portion has a non-decorative region made of a smooth surface provided at least in two locations in the tire circumferential direction,
When the sum of the angles formed by two straight lines connecting both ends in the tire circumferential direction of each undecorated region and the tire rotation center O ₁ is ω, 0.4 ≦ (2π−ω) /2π≦0.8 Preferably there is.

It is preferable that the rubber member used for the sidewall portion has a hardness according to JIS of 45 to 60.

According to the pneumatic tire, air resistance during rolling of the tire can be reduced, and unevenness caused by the tire structure and the like can be made inconspicuous on the sidewall surface.

It is a profile sectional view of the pneumatic tire of this embodiment. It is the figure which showed the surface of the side part of this embodiment. It is the elements on larger scale of the pattern area | region of the side wall of the side part of this embodiment. It is the elements on larger scale of the pattern area | region of the side wall of the side part of this embodiment. It is the elements on larger scale of the pattern area | region of the side wall of the side part of this embodiment. It is the elements on larger scale of the pattern area | region of the side wall of the side part of this embodiment. It is the elements on larger scale of the pattern area | region of the side wall of the side part of this embodiment. It is the elements on larger scale of the pattern area | region of the side wall of the side part of this embodiment. It is the elements on larger scale of the pattern area | region of the side wall of the side part of this embodiment. It is the elements on larger scale of the pattern area | region of the side wall of the side part of this embodiment. It is the elements on larger scale of the pattern area | region of the side wall of the side part of this embodiment.

Hereinafter, the pneumatic tire of the present embodiment (hereinafter simply referred to as a tire) will be described in detail.
The pneumatic tire of this embodiment described below is applied to, for example, a tire for a passenger car, but can also be applied to a tire for a small truck or a tire for a bus / truck. The pneumatic tire of this embodiment described below is a passenger tire.
In the following description, the tire width direction is a direction parallel to the rotation axis of the pneumatic tire.
The outer side in the tire width direction is the side away from the tire center line CL representing the tire equatorial plane in the tire width direction. Further, the inner side in the tire width direction is a side closer to the tire center line CL in the tire width direction. The tire circumferential direction is a direction that rotates around the rotation axis of the pneumatic tire as the center of rotation. The tire radial direction is a direction orthogonal to the rotation axis of the pneumatic tire. The outer side in the tire radial direction refers to the side away from the rotation axis. The inner side in the tire radial direction refers to the side approaching the rotation axis.

(Tire structure)
FIG. 1 shows a profile cross-sectional view of a tire 10 of the present embodiment. The tire 10 includes a tread portion 10T having a tread pattern, a pair of bead portions 10B, and a pair of bead portions 10B and a pair of side portions 10S that are connected to the tread portion 10T. Prepare. In FIG. 1, only one side of the tire center line CL is shown.
The tire 10 includes a carcass ply layer 12, a belt layer 14, and a bead core 16 as a skeleton material. Around these skeleton materials, a tread rubber member 18, a side rubber member 20, and a bead filler rubber member 22. And a rim cushion rubber member 24 and an inner liner rubber member 26.

The carcass ply layer 12 is made of a carcass ply material in which organic fibers are covered with rubber. The carcass ply material is wound between a pair of annular bead cores 16 and extends outward in the tire radial direction, so that the carcass ply layer 12 has a toroidal shape. A belt layer 14 is provided outside the carcass ply layer 12 in the tire radial direction. The belt layer 14 is composed of two belt members 14a and 14b. The belt members 14a and 14b are members in which rubber is coated on a steel cord disposed at a predetermined angle, for example, 20 to 30 degrees with respect to the tire circumferential direction. The lower belt material 14a has a longer width in the tire width direction than the upper belt material 14b. The inclination directions of the steel cords of the two-layer belt materials 14a and 14b are opposite to each other. For this reason, the steel cords of the belt members 14a and 14b are interlaced. The belt members 14a and 14b suppress the expansion of the carcass ply layer 12 due to the filled air pressure.

A tread rubber member 18 is provided on the outer side of the belt layer 14 in the tire radial direction. Side rubber members 20 that form side portions are connected to both ends of the tread rubber member 18. A rim cushion rubber member 24 is provided at the inner end in the tire radial direction of the side rubber member 20. The rim cushion rubber member 24 comes into contact with a rim on which the tire 10 is mounted. A bead filler rubber member 22 is provided on the outer side in the tire radial direction of the bead core 16 so as to be sandwiched between the carcass ply layers 12 wound around the bead core 16. An inner liner rubber member 26 that suppresses air leakage is provided on the inner surface of the tire 10. The inner surface of the tire 10 faces a tire cavity region that is filled with air surrounded by the tire 10 and the rim.
In addition, the tire 10 includes a two-layer belt cover layer 30 formed by coating organic fibers with rubber. The belt cover layer 30 covers the belt layer 14 from the outer side in the tire radial direction of the belt layer 14. Further, the tire 10 may include a bead reinforcing material between the carcass layer 12 and the bead filler rubber member 22.
The tire structure of the tire 10 of the present embodiment is not limited to the above structure, and may be a known structure or a novel structure. The tread pattern of the tire 10 of the present embodiment is not particularly limited.

(Sidewall pattern)
FIG. 2 is a view showing the surface of the side portion 10S.
The side portion 10S has an information display area 32, a pattern area 34, and an undecorated area 36 on the sidewall surface. Such a sidewall pattern of the side portion 10S is provided on both side surfaces of the pneumatic tire, but may be provided only on one side surface. When provided only on one side surface, it is preferable to provide the pattern region 34 of the present embodiment on the surface of the tire 10 that faces the outside of the vehicle when mounted on the vehicle.

The information display area 32 is provided adjacent to the inner side in the tire radial direction of the pattern area 34 along the bead portion 10B. Information such as the tire size, model number, and country of manufacture is written in the information display area 32.
The non-decorative region 36 is formed of a smooth surface where the valley portion 50 is not provided, and is provided adjacent to the pattern region 34 on the periphery of the side portion 10S. The undecorated region 36 is preferably provided at at least two locations in the tire circumferential direction. In the undecorated area 36, a mark such as a tire name and a tire manufacturer's trademark may be displayed.
The undecorated region 36 has a certain width in the tire radial direction. The length of the undecorated region 36 in the tire circumferential direction is provided so as to increase toward the outer side in the tire radial direction. Here, as shown in FIG. 2, the angles formed by two straight lines connecting both ends of the arc in the tire radial direction outer peripheral side of each undecorated region 36 and the tire rotation center O ₁ are ω ₁ , ω ₂ , When ω ₁ ′ and ω ₂ ′ are angles formed by two straight lines connecting both ends of the arc on the inner circumferential side in the tire radial direction of the region 36 and the tire rotation center, ω ₁ > ω ₁ ′ and ω ₂ > ω ₂ 'Is preferred.
Here, when the sum of ω ₁ and ω ₂ is ω, it is preferable that 0.4 ≦ (2π−ω) /2π≦0.8. If it is this range, the effect which makes the pattern area | region 34 make the unevenness | corrugation resulting from a tire structure etc. not conspicuous in the sidewall 10S surface can be ensured.

The pattern area 34 is provided adjacent to the outer side of the information display area 32 in the tire radial direction so as to go around the side portion 10S. The pattern area 34 is a position where an undecorated area 36 in the tire circumferential direction is provided, and the height in the tire radial direction is small.
The pattern region 34 is provided in a region having a distance of 30% to 80% of the tire cross-section height H in the tire radial direction from the innermost end portion in the tire radial direction of the sidewall portion. This is preferable in that it is attracted to the side pattern by a periodic change in the size of the recess 60. Here, as shown in FIG. 1, the tire cross-section height H is a radial direction in which the distance from the tire rotation center of the tread portion 10 </ b> T is maximum from the innermost end portion of the tire bead portion 10 </ b> B in the tire radial direction. This is the distance in the tire radial direction to the position.
The pattern area 34 includes the tire maximum width position. The tire maximum width position refers to a position in the tire radial direction where the tire width in the tire width direction is maximum. Specifically, the tire width refers to the maximum width between the side portions on both sides obtained by mounting on a rim determined by JATMA, ETRTO or TRA and filling with a predetermined air pressure.

FIG. 3 is a partially enlarged view of the pattern region 34 on the side wall surface of the side portion 10S. The pattern region 34 is provided with a plurality of linear valley portions 50 and a plurality of concave portions (circled portions in FIG. 2) 60.
The direction in which the plurality of valley portions 50 extend may be any direction, but is preferably provided in a region excluding the inside of the concave portion 60 of the pattern region 34 so as to extend radially in the tire radial direction.
By providing the valley 50, a ridge 52 is formed between the valleys 50 adjacent to each other, and a serration pattern composed of the valley 50 and the ridge 52 is formed. For example, unevenness is formed on the surface of the vulcanization mold by serration processing, and the tire is pressure-cured in the vulcanization mold at the time of vulcanization, whereby the pattern region 34 on the surface of the sidewall 10S of the tire 10 is The valley 50 and the ridge 52 can be formed.

When serration processing is performed on the pattern region 34 (when the pattern region 34 has a serration pattern), the ratio of the total area of the plurality of recesses 60 to the area of the serrated portion (portion having the serration pattern) is 25%. It is preferable to be 60% from the viewpoint of reducing air resistance. When the area ratio is less than 25%, the air resistance cannot be reduced, and the recess 60 becomes too sparse, and the pattern in the pattern region 34 hardly attracts the viewer's line of sight. The appearing irregularities are easily recognized. When the area ratio exceeds 60%, the air resistance cannot be reduced. The area ratio is more preferably 30 to 45%.

The recess 60 has a dimple shape that is recessed in a spherical shape, and the contour of the recess 60 is preferably circular.
The plurality of concave portions are n (n is a natural number of 2 or more) provided at equal intervals on the first arc C ₁ having a constant radius R ₁ centered on the tire rotation center O ₁ in a side view of the tire. Out of the points, n recess rows are arranged at equal intervals and spaced apart from each other on a plurality of second arcs C ₂ having a constant radius R ₂ centered on any point O ₂ . Here, “equal intervals” means that the distances (center intervals) between the centers of the recesses 60 are equal. In addition, if the recessed part 60 is not circular, it means that the distance between the gravity centers of the recessed part 60 is equal intervals. The pattern region 34 has n number of such recess rows. Here, it is preferable that the sum of R ₁ and R ₂ is larger than the tire diameter, and the absolute value of the difference between R ₁ and R ₂ is smaller than the tire diameter.
In pattern area 34, the second circular arc C ₂ to each other so as to identify the look person adjacent interval of the second circular arc C ₂ adjacent to each other, rather than the center spacing of the plurality of recesses 60 with each other on the second circular arc C2 Wide is preferable. That is, a plurality of recesses 60, the distance to the other recesses 60 which are adjacent on the same second circular arc C ₂ is preferably less than the distance to the recess 60 on the other second circular arc C ₂ adjacent . For this reason, it is preferable that the space | interval of adjacent center O2 of _2nd circular arc is wider than the center space | interval of several recessed part 60 on 2nd circular arc C2.

The contour shape of the recess 60 is not limited to a circle, but may be an elliptical shape or a shape close to a polygonal shape (for example, a rectangle). The equivalent circle diameter of the recess 60 (the diameter of a circle having the same area as the occupied area) is larger than the interval between the valley portions 50. Here, the area occupied by the recess 60 is the area occupied by the recess 60 on the surface of the sidewall 10S. If the contour shape of the recess 60 is circular, the equivalent circle diameter is equal to the diameter. The equivalent circle diameter of the recess 60 is, for example, 1.0 to 5.0 mm. If the equivalent circle diameter of the recess 60 is smaller than 1.0 mm, turbulent flow of the air surrounding the rolling tire 10 due to the recess 60 is difficult to occur. For this reason, the effect of reducing the air resistance due to laminar flow is reduced, and the fuel consumption of the traveling vehicle is deteriorated. Further, if the equivalent circle diameter of the recess 60 is smaller than 1.0 mm, it is difficult to process the vulcanization mold, the accuracy of the mold is insufficient, and the visibility of each recess 60 is deteriorated, resulting in the tire structure and the like. The effect that the unevenness is not conspicuous on the surface of the sidewall 10S is reduced. On the other hand, when the equivalent circle diameter of the recess 60 is larger than 5.0 mm, the visibility of each recess 60 is deteriorated, and the effect of not conspicuous unevenness due to the tire structure or the like on the surface of the sidewall 10S is reduced.
The equivalent circle diameter of the recess 60 is preferably 3 to 10 times the interval between the adjacent valley portions 50.

In the present embodiment, each of the plurality of concave portions 60 and the plurality of valley portions 50 has the same depth, but does not necessarily have the same depth. The larger the concave portion 60 is, the larger the groove depth is. It may be deep.
The depth of the recess 60 from the sidewall surface is preferably deeper than the depth of the valley 50 from the sidewall surface. Specifically, the depth of the recess is preferably 0.3 to 1.5 mm. Here, the sidewall surface serving as a reference for the depth refers to the smooth surface 56 of the non-decorated region 36. By making the depth of the recess 60 deeper than the depth of the valley 50, it is possible to effectively prevent the appearance defect caused by air collecting between the tire sidewall and the vulcanization mold surface during vulcanization. And air resistance can be effectively reduced.
As a rubber material of the side portion 10S of the pattern region 34, hardness (hardness measured using a type A durometer at a temperature of 20 ° C. in accordance with a durometer hardness test specified in JIS K6253) of 45 to 60 Rubber can be used. When rubber having such hardness is used, poor appearance due to air retention during vulcanization hardly occurs.

<Modification>
In the pattern region 34, as shown in FIGS. 4A, 4B, 5A, and 5B, the equivalent circular diameter of the plurality of recesses is the circumferential direction on the first arc at the center of the second arc in which the recesses are arranged. You may change periodically according to a position. In the range of FIG. 4A, the equivalent circle diameter of the recess 60 increases as the second arc moves to the right side of FIG. 4A. In the range of FIG. 4B, the second arc moves to the right side of FIG. 4B. Accordingly, the equivalent circle diameter of the recess 60 is reduced. 5A, the equivalent circle diameter of the recess 60 in the second arc at the center in the left-right direction is the largest, and the equivalent circle diameter of the recess 60 arranged in the second arc toward the left side and the right side in FIG. 5A. Is decreasing. In the range of FIG. 5B, the equivalent circle diameter of the recess in the second arc at the center in the left-right direction is the smallest, and the equivalent circle diameter of the recess arranged in the second arc toward the left and right sides in FIG. Yes. Thus, the equivalent circle diameter of the recess 60 may periodically change according to the circumferential position of the tire.

As shown in FIGS. 6A and 6B, in the pattern region 34, the equivalent circle diameters of the plurality of recesses may be periodically changed according to the circumferential position of the second arc. In the range of FIG. 6A, the equivalent circle diameters of the plurality of recesses 60 on the same second arc are the largest at the central portion in the left-right direction of FIG. 6A and decrease toward the left side and the right side of FIG. In the range of FIG. 6B, the equivalent circle diameter of the concave portion 60 on the same second arc is the smallest at the central portion in the left-right direction and increases toward the left side and the right side of FIG. 6B. Thus, the equivalent circle diameter of the recess 60 may periodically change according to the circumferential position of the tire.

7A, on the same second arc, the equivalent circle diameter of the recess 60 may be larger toward the inner side in the tire radial direction, and the equivalent circle diameter of the recess 60 may be decreased toward the outer side in the tire radial direction. As shown in FIG. 7B, on the same second arc, the equivalent circle diameter of the recess 60 may be smaller toward the inner side in the tire radial direction, and the equivalent circle diameter of the recess 60 may increase toward the outer side in the tire radial direction.

It is preferable that the equivalent circle diameter of the recess 60 has a change of at least three steps. The change in the equivalent circle diameter of the recess 60 may be a continuous change or an intermittent change. A person who looks at the surface of the sidewall 10S is further deprived of by the change in the size of the recess 60, and the unevenness caused by the tire structure or the like is overlooked on the surface of the sidewall 10S and becomes inconspicuous.

The maximum depth of the recess 60 is preferably constant regardless of the size of the equivalent circle diameter. In particular, when the recess 60 has a circular shape and the bottom surface of the recess 60 has a spherical shape and is recessed, the edge of the largest recess 60 can be obtained by making the maximum depth constant regardless of the size of the recess 60. Since the inclination angle in the depth direction of the bottom surface in the vicinity is smaller than the inclination angle in the depth direction of the bottom surface in the vicinity of the edge of the smallest concave portion 60, the light reflection angle on the bottom surface of the concave portion 60 is the size of the concave portion 60. It depends on. For this reason, since the person who sees the sidewall surface can recognize the sidewall pattern not only by the change in the size of the recess 60 but also by the reflection characteristics of the recess 60, the viewer can see the first pattern by the pattern in the pattern region 34. Because it is taken away, the irregularities that actually appear on the sidewall surface are overlooked and become inconspicuous.

(Example, conventional example, comparative example)
In order to investigate the effect of this embodiment, a tire having a sidewall pattern as shown in FIG. 2 was produced. The size of the produced tire is 195 / 65R15 91H. Whether or not the manufactured tire was viewed from a distance of 1 m from the tire, and whether or not the irregularities actually appearing on the tire sidewall surface (excluding serrations and irregularities due to the concave portions 60) were visually recognized (surface) The visibility of the unevenness was investigated.

Regarding the visibility of surface irregularities,
・ When the unevenness actually appearing by more than 95 observers (viewers) out of 100 is not clearly recognized, the rating is 110.
・ When the unevenness actually appearing between 90 and 94 observers out of 100 cannot be clearly recognized, the score is 108.
・ When the unevenness actually appearing between 80 and 89 observers out of 100 cannot be clearly recognized, the score is 106.
・ When the unevenness actually appearing in 70 to 79 out of 100 observers cannot be clearly recognized, the score is 104,
・ When the unevenness actually appearing between 60 and 69 observers out of 100 cannot be clearly recognized, the score is 102.
・ When 100 or more out of 100 observers cannot clearly recognize the irregularities actually appearing, the score is 100.
A score of 97 was given when 49 or less of 100 observers could not clearly recognize the irregularities actually appearing.

Tables 1 and 2 below show the specifications and evaluation results of Examples 1 to 7, conventional examples, and comparative examples 1 and 2, respectively.
In Examples 1 to 7, a predetermined radius R ₂ centered on a point on the circumference (first arc) of a circle having a predetermined radius R ₁ (R ₁ > 0) centered on the tire rotation center O ₁ . On the arc (second arc), a plurality of recesses 60 were provided at equal intervals. Here, R ₁ = 250.0 mm and R ₂ = 50.0 mm.
In the conventional example and the comparative examples 1 and 2, a plurality of recesses 60 are provided at equal intervals (R ₁ = 0) on the circumference of a plurality of concentric circles having a center at the tire rotation center O ₁ and different radii.
In Comparative Example 3, a plurality of concave portions are formed on an arc having a predetermined radius R ₂ centered on a point on the circumference of a circle having a predetermined radius R ₁ (R ₁ > 0) centered on the tire rotation center O _1. 60 were provided at non-uniform intervals so that the intervals between the recesses 60 increased toward the outer side in the tire radial direction.
In the conventional example, the comparative example 3, and the examples 1 to 7, serrations were applied to portions other than the formation of the concave portions 60 in the pattern region. The interval between the valley portions 50 was 1.0 mm. In Comparative Examples 1 and 2, serration processing was not performed.
The shape of the recess 60 is a perfect circular recess, and the bottom surface of the recess 60 is spherical. The number of types of diameters of the recesses, the values of the diameter, and the depth were as shown in Tables 1 and 2. When the number of types of the diameters of the recesses 60 is plural, the diameters of the recesses 60 are arranged so as to periodically change in the tire circumferential direction.
Tables 1 and 2 show the values of (2π−ω) / 2π where ω is the sum of the angles formed by the two straight lines connecting the tire circumferential ends of each undecorated region and the tire rotation center O _1. It was as follows. In Comparative Examples 1 and 2, no undecorated region was provided.

Examples 1-7 shown in Table 1, prior art, and Comparative Example 1 than Comparative to 3, a predetermined radius centered on a point on the first arc of a predetermined radius centered on the tire rotation center O ₁ It can be seen that the visibility of the surface irregularities can be suppressed by providing a plurality of recesses 60 at equal intervals on the second arc.
From the evaluation results of Examples 1 to 7, it can be seen that the greater the type of size of the recess 60, the more the visibility on the surface of the sidewall 10S of the unevenness caused by the tire structure or the like can be suppressed.
From the above, in the tire 10 of the present embodiment, it can be said that the unevenness caused by the tire structure and the like can be made inconspicuous on the surface of the sidewall 10S by the pattern of the recess 60 that reduces the air resistance during tire rolling.

As mentioned above, although the pneumatic tire of this invention was demonstrated in detail, this invention is not limited to the said embodiment and Example, In the range which does not deviate from the main point of this invention, what may be improved and changed variously. Of course.

Claims

A pneumatic tire having a sidewall portion,
The sidewall portion is
Of n points (n is a natural number of 2 or more) provided at equal intervals on the first arc with a constant radius R 1 centered on the tire rotation center O 1 , one of the points O 2 is the center. constant radius R having n comprises pattern area a recess string having a second plurality of dimple-like recesses which are arranged at equal intervals on the second circular arc, pneumatic tire.
The pneumatic tire according to claim 1, wherein an interval between the adjacent second arcs is wider than a center interval between the plurality of concave portions on the second arc.
The equivalent circle diameter of each of the plurality of recesses periodically varies according to a circumferential position on the first arc at the center of a second arc in which each of the recesses is located. Or the pneumatic tire of 2.
The pneumatic tire according to claim 1 or 2, wherein the equivalent circle diameter of each of the plurality of recesses periodically varies according to a circumferential position of a second arc in which each of the recesses is located. .
The pneumatic tire according to any one of claims 1 to 4, wherein an equivalent circle diameter of each of the plurality of recesses periodically varies according to a position in a circumferential direction of the tire.
The pneumatic tire according to any one of claims 1 to 4, wherein an equivalent circle diameter of each of the plurality of recesses varies depending on a position in a radial direction of the tire.
The pneumatic tire according to any one of claims 1 to 6, wherein the equivalent circle diameter of the recess is 1.0 to 5.0 mm.
The pneumatic tire according to any one of claims 1 to 7, wherein a depth of the concave portion is 0.3 to 1.5 mm.
The air according to any one of claims 1 to 8, wherein a plurality of linear valleys extending in one direction are provided in a portion of the pattern region other than the portion where the plurality of recesses are formed. Enter tire.
The pneumatic tire according to claim 9, wherein a ratio of a total area of the plurality of concave portions to an area of a portion provided with the plurality of linear valley portions is 25% to 60%.
11. The pattern area according to claim 1, wherein the pattern area is provided in an area at a distance of 30% to 80% of a tire cross-sectional height in a tire radial direction from an innermost end portion in a tire radial direction of the sidewall portion. A pneumatic tire according to claim 1.
The sidewall portion has a non-decorative region made of a smooth surface provided at least in two locations in the tire circumferential direction,
0.4 ≦ (2π−ω) /2π≦0.8, where ω is the sum of the angles formed by two straight lines connecting both ends in the tire circumferential direction of each undecorated region and the tire rotation center, The pneumatic tire according to any one of claims 1 to 11.
The pneumatic tire according to any one of claims 1 to 12, wherein a rubber member used for the sidewall portion has a hardness according to JIS of 45 to 60.