Pneumatic tire

Abstract

To provide a tire that achieves both reduction of air resistance and enhancement in traction performance.SOLUTION: This pneumatic tire includes a tread, a sidewall, and a bead. The sidewall has a plurality of recesses that are arranged in a repeated and periodic manner along the tire circumferential direction between a maximum width position of the tire and a buttress portion.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that achieves both suppression of air resistance and improvement of traction performance.

Background Art

[0002] Conventionally, pneumatic tires having side blocks on the sidewalls have been widely known. The side blocks are periodically and repeatedly arranged in the tire circumferential direction, and promote the discharge of mud and water during off-road driving to improve the traction performance of the tire (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in recent years, from the viewpoint of improving the fuel efficiency performance of vehicles, etc., reduction of air resistance has also been demanded for tires. The side blocks may disrupt the air flow around the vehicle and increase air resistance, but conventional tires have not been sufficiently considered for reducing air resistance and there is great room for improvement.

[0005] An object of the present invention is to provide a tire that achieves both suppression of air resistance and improvement of traction performance.

Means for Solving the Problems

[0006] A pneumatic tire according to one aspect of the present invention includes a tread, a sidewall, and a bead, and the sidewall is characterized in that it has recesses periodically and repeatedly arranged in the tire circumferential direction between the tire maximum width position and the buttress portion.

Effects of the Invention

[0007] The pneumatic tire according to the present invention has excellent traction performance while effectively reducing air resistance.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0009] Hereinafter, an example of an embodiment of the pneumatic tire according to the present invention will be described in detail with reference to the drawings. The embodiment described below is merely an example, and the present invention is not limited to the following embodiment. Also, in the following, the same reference numerals are given to equivalent elements in all the drawings, and redundant explanations are omitted. Note that a form formed by selectively combining the constituent elements of a plurality of embodiments and modification examples described below is included in the present invention, and the embodiments described below can be appropriately modified within a range that does not impair the object of the present invention.

[0010] <First Embodiment> Hereinafter, a pneumatic tire 1 which is an example of an embodiment will be described with reference to FIGS. 1 to 4.

[0011] FIG. 1 is a perspective view of a pneumatic tire 1 according to an example of an embodiment. As shown in FIG. 1, the pneumatic tire 1 includes a tread 2 which is a portion in contact with the road surface, a sidewall 3 which forms the side surface of the tire, and a bead 4 which is a portion fixed to the rim of the wheel. The tread 2, the sidewall 3, and the bead 4 are formed in an annular shape along the tire circumferential direction. In this specification, in a plan view of the pneumatic tire 1, the portion between the surface of the shoulder blocks 10, 11 facing radially outside of the tire diameter and the boundary between the tread 2 and the sidewall 3 (corresponding to the side surfaces 10a, 11a, etc. described later) is referred to as a buttress portion.

[0012] The tread 2 has a tread pattern including a plurality of blocks such as the shoulder blocks 10, 11. Further, a plurality of grooves such as grooves 12, 13 for partitioning the blocks are formed in the tread 2.

[0013] The shoulder blocks 10, 11 are blocks formed in the outer portion in the tire axial direction of the tread 2 and are arranged alternately in the tire circumferential direction. The shoulder blocks 10, 11 have, for example, the same size as each other, but are different in shape in that the side surface 11a of the shoulder block 11 is recessed more than the side surface 10a of the shoulder block 10. The side surface 10a of the shoulder block 10 is smoothly inclined from the boundary with the sidewall 3 to the surface of the shoulder block 10. The side surface 11a of the shoulder block 11 has a step between the boundary with the sidewall 3 and the surface of the shoulder block 11, and the vicinity of the surface of the shoulder block 11 is more deeply recessed than the vicinity of the boundary with the sidewall 3.

[0014] The shoulder blocks 10, 11 are divided by grooves 12, 13 extending in the tire axial direction. The groove 12 is formed with substantially the same width from between the blocks to the boundary with the sidewall 3. The groove 13 widens near the boundary with the sidewall 3. The side surfaces 10a, 11a of the shoulder blocks 10, 11 and the grooves 12, 13 form irregularities in the circumferential direction of the tire in the buttress portion of the pneumatic tire 1. These irregularities improve the traction performance on muddy, sandy, or snowy roads.

[0015] The sidewall 3 extends radially inward from both axial ends of the tread 2 in the tire axial direction and, together with the bead 4, forms the left and right side surfaces of the pneumatic tire 1. The sidewall 3 has a side rib 20 between the tire maximum width position P and the buttress portion. The side rib 20 is a convex portion protruding outward in the tire axial direction and is formed annularly along the tire circumferential direction. In this specification, the "tire maximum width position P" means the position where the axial length in the tire axial direction is maximum on the profile surface 3a of the sidewall 3 (see FIG. 4 described later). Also, the "profile surface 3a" of the sidewall 3 means the surface facing the outside in the tire axial direction of the sidewall 3 when the side rib 20 is not formed.

[0016] The sidewall 3 has a recess 21 recessed with respect to the outer surface 20S of the side rib 20. The recesses 21 are periodically and repeatedly arranged in the tire circumferential direction. Although details will be described later, the pneumatic tire 1 having the side rib 20 and the recess 21 in the sidewall 3 can effectively reduce air resistance and have excellent traction performance. The plurality of recesses 21 are arranged at a predetermined interval in the tire circumferential direction. This predetermined interval may be constant as in the example shown in FIG. 2, or may be a variable pitch in which the interval between the blocks is slightly changed in units of a predetermined number.

[0017] In the present embodiment, the recess 21 includes a first recess 22 and a second recess 23, and the recesses 21 having substantially the same shape and the same size are arranged in the tire circumferential direction. Note that the arrangement of the recesses 21 is not limited to this example, and two or more types of recesses 21 having different shapes from each other may be arranged alternately or in a predetermined pattern in the tire circumferential direction. The number of the recesses 21 arranged in the tire circumferential direction is not particularly limited, but as an example, it is 20 or more and 30 or less.

[0018] The tread 2 and the sidewall 3 are generally made of different types of rubber. The bead 4 has, for example, a bead core and a bead filler. The bead core is a ring-shaped member in which a bundled steel wire (bead wire) is coated with rubber. The bead filler is made of rubber harder than the tread rubber and the sidewall rubber and has a function of enhancing the rigidity of the bead 4.

[0019] The pneumatic tire 1 includes, for example, a carcass, a belt, and an inner liner (not shown in FIG. 1) inside. The carcass is a cord layer coated with rubber and forms the skeleton of the pneumatic tire 1 that withstands loads, impacts, air pressure, etc. The belt is a reinforcing band disposed between the rubber constituting the tread 2 and the carcass. The belt strongly tightens the carcass to increase the rigidity of the pneumatic tire 1. The inner liner is a rubber layer provided on the inner peripheral surface of the carcass and holds the air pressure of the pneumatic tire 1.

[0020] FIG. 1 shows the left side surface of the pneumatic tire 1, and the pneumatic tire 1 preferably has side ribs 20 and recesses 21 on the left and right sidewalls 3. Note that the recesses 21 on the left and right are not limited to depressions having the same shape, and may have completely different shapes. The recess 21 on the right side surface has, for example, a shape obtained by rotating the recess 21 on the left side surface 180° with respect to the center line passing through the tire equator and perpendicular to the tire rotation axis. The pneumatic tire 1 may be a tire without a specified mounting direction.

[0021] The pneumatic tire 1 is suitable for, for example, tires for light trucks. Note that light trucks include pickup trucks, sports utility vehicles (SUVs), etc. An example of the size of the pneumatic tire 1 is LT275 / 60R20.

[0022] Next, while referring to FIG. 2, the sidewall 3 and the battless portion of the pneumatic tire 1 will be described in detail. FIG. 2 is a left side view of the pneumatic tire 1 and is an enlarged view of a portion including the sidewall 3 and the battless portion. Hereinafter, the first direction in the tire circumferential direction may be referred to as the "X1 direction", and the second direction may be referred to as the "X2 direction". Also, the direction facing the outer side in the tire radial direction may be referred to as the "Y1 direction", and the direction facing the inner side in the radial direction may be referred to as the "Y2 direction".

[0023] As shown in FIG. 2, the sidewall 3 has a side rib 20 which is a convex portion protruding outward in the tire axial direction between the battless portion and the tire maximum width position P. Thereby, the pneumatic tire 1 can obtain good side cut (protection) performance. The outer surface 20S of the side rib 20 may have substantially the same height over the entire surface with reference to the profile surface 3a.

[0024] The sidewall 3 has a plurality of recesses 21 formed on the outer surface 20S of the side rib 2. One recess 21 is a depression formed by connecting one first recess 22 and one second recess 23. A step is formed at the boundary 24 between the first recess 22 and the second recess 23, and the first recess 22 is more deeply recessed than the second recess 23.

[0025] In the present embodiment, the side rib 20 has an annular continuous portion 25 continuous in the tire circumferential direction at the end portion on the inner side in the tire radial direction. Due to the continuous portion 25, an air flow along the surface of the sidewall 3 is generated during running, and the air resistance is effectively reduced.

[0026] Due to the recess 21 formed on the side rib 20, irregularities are formed in the circumferential direction of the tire on the portion located between the buttress portion of the sidewall 3 and the tire maximum width position P. These irregularities improve the traction performance on muddy ground, sandy ground, or snowy roads. From the perspective of improving traction performance, it is preferable that the length of the recess 21 along the circumferential direction of the tire is longer than the interval between the recesses 21.

[0027] The recess 21 and the shoulder blocks 10, 11 of the tread 2 are preferably arranged in a regular pattern related to each other. Thereby, a regular pattern is formed integrally with the recess 21 and the buttress portion, for example, the traction performance is stabilized and the effect of reducing air resistance is also improved. In the present embodiment, the first recess 22 is formed so as to be aligned with the shoulder block 10 in the tire radial direction, and the second recess 23 is formed so as to be aligned with the shoulder block 11 in the tire radial direction. The second recess 23 is larger than the first recess 22, and a part of it extends to a position overlapping the shoulder block 10 in the tire radial direction.

[0028] The groove 12 is formed in a range overlapping the recess 21 in the tire radial direction, the groove 13 is formed in a range not overlapping the recess 21 in the tire radial direction, and the recess 21 is formed at the same pitch as the pair of shoulder blocks 10, 11 in the circumferential direction of the tire. The interval between the recesses 21 is wider on the tire maximum width position P side than on the buttress portion side. Thereby, the mud discharging property becomes good on muddy ground and the traction performance is further improved.

[0029] As described above, the first recess 22 and the second recess 23 have different depths from each other, and the first recess 22 is formed deeper. The depth of the recess 21 (see FIG. 4 described later) means the length along the normal direction of the profile surface 3a from the profile surface 3a of the sidewall 3 to the bottom surface of the recess. Due to the height difference between the first recess 22 and the second recess 23 constituting the recess 21, and the height difference between the side rib 20 existing between the recesses 21, irregularities are formed on the sidewall 3, and these irregularities improve the traction performance on muddy ground, sandy ground, or snowy roads.

[0030] The first recess 22 has substantially the same height except for the peripheral end where the first recess 22 contacts the periphery. The second recess 23 has three regions (a first region 231, a second region 232, and a third region 233) with different depths along the tire radial direction. The depth of the second recess 23 is substantially constant in the first region 231 adjacent to the side rib 20, and is deepest at the boundary between the second region 232 and the third region 233. The continuous part 25 is formed at substantially the same height with respect to the profile surface 3a.

[0031] In the first recess 22, the portion located on the inner side in the tire radial direction (the Y2 - direction side) protrudes in the X1 direction. This protruding portion 220 is formed, for example, in a length range of 30% or more and 70% or less of the tire - radial length of the first recess 22 from the inner - side end in the tire radial direction. In other words, in the first recess 22, the portion located on the outer side in the tire radial direction (the Y1 - direction side) is recessed in the X2 direction. Such unevenness of the first recess 22 contributes to the improvement of traction performance. The X1 - direction end of the protruding portion 220 is formed substantially linearly in side view along the tire radial direction.

[0032] The peripheral end of the recess 21 has an inclination such that the depth of the depression gradually becomes deeper. The peripheral end of the recess 21 may be formed perpendicular to the outer surface 20S of the side rib 20. At the end of the protruding portion 220 of the first recess 22, a slope 221 with a gentler inclination than the other peripheral ends is formed. The slope 221 is located at the peripheral end facing the Y1 direction. By forming a gentle slope 221 at the Y1 - direction end of the protruding portion 220, an air flow along the surface of the sidewall 3 is likely to occur, and an increase in air resistance can be suppressed. The inclination angle of the slope 221 with respect to the outer surface 20S of the side rib 20 is, for example, 40° or more and 75° or less.

[0033] The boundary 24 between the first recess 22 and the second recess 23 extends from the outer - side end in the tire radial direction of the recess 21 to the inner side in the tire radial direction (the Y2 - direction side), and bends in the X1 direction near the center in the tire radial direction of the recess 21. Therefore, the portion of the first recess 22 located on the Y2 - direction side has a gradually decreasing tire - circumferential length in the Y2 direction.

[0034] As described above, the depth of the second recess 23 changes in the tire diameter direction, and the first region 231 is the shallowest. The second region 232 adjacent to the first region 231 in the Y2 direction is inclined so as to gradually become deeper in the Y2 direction, and the third region 233 adjacent to the second region 232 in the Y2 direction is inclined so as to gradually become shallower in the Y2 direction. By providing a gentle slope on the surface of the second side block 20, an air flow along the surface of the second side block 20 is likely to occur, and an increase in air resistance can be suppressed.

[0035] The second recess 23 is inclined with respect to the tire diameter direction such that the peripheral end facing the X2 direction is gradually positioned in the X1 direction in the Y2 direction. Therefore, the second recess 23 has a tapered shape in which the tire circumferential length is slightly shorter at the Y2 direction end than at the Y1 direction end.

[0036] In a plan view of the side surface of the pneumatic tire 1, the area of the recess 21 is preferably 20% to 60% of the area of the region between the grounding end E and the tire maximum width position P. Thereby, the effect of the present invention of achieving both suppression of air resistance and improvement of traction performance becomes more remarkable. In this specification, the grounding end E means the tire axial end of the region that contacts the flat road surface when a load of 85% of the normal load (maximum load capacity) at the normal internal pressure is applied in a state where the unused pneumatic tire 1 is mounted on a normal rim and filled with air to reach the normal internal pressure.

[0037] Next, with reference to FIGS. 3 and 4, the cross-sectional shapes of the side rib 20 and the recess 21 formed in the sidewall 3 will be described in detail. FIG. 3 is a cross-sectional view showing a part of the cross-section taken along line A-A in FIG. 2, and FIG. 4 is a cross-sectional view showing a part of the cross-section taken along line B-B in FIG. 2. In FIG. 2, the line A-A passes through the approximate center of the groove 13 in the tread 2 and passes through the outer surface 20S of the side rib 20 where the recess 21 is not formed in the sidewall 3. Further, the line B-B passes through the shoulder block 11 in the tread 2 and passes through the first recess 22 in the sidewall 3.

[0038] As shown in FIG. 3, the side rib 20 is a convex portion that protrudes outward in the tire axial direction from the profile surface 3a of the sidewall 3 on the sidewall 3. The outer surface 20S of the side rib 20 has substantially the same height with respect to the profile surface 3a from the inner side to the outer side in the tire radial direction.

[0039] The height H of the side rib 20 with respect to the profile surface 3a is, for example, 1 mm to 15 mm. If H is within this range, it is possible to obtain the pneumatic tire 1 having good side cut performance, effectively reducing air resistance, and having excellent traction performance at the same time. The height H of the side rib 20 means the length along the normal direction of the profile surface 3a from the profile surface 3a to the highest portion of the side rib 20.

[0040] As shown in FIG. 4, the recess 21 is formed in the side rib 20, and a continuous portion 25 is formed at the end of the side rib 20 on the inner side in the tire radial direction. The distance L1 between the continuous portion 25 and the tire maximum width position P is, for example, 1% to 20% with respect to the distance L2 between the ground contact end D and the tire maximum width position P. If L1 / L2 is within this range, the effect of the present invention becomes more remarkable. Note that L1 and L2 are distances along the tire radial direction. That is, in FIG. 4, L1 is the length of the perpendicular dropped in the tire radial direction from the continuous portion 25 to the tire maximum width position P, and L2 is the length of the perpendicular dropped in the tire radial direction from the ground contact end E to the tire maximum width position P.

[0041] The maximum depth D1 of the recess 21 with respect to the outer surface 20S of the side rib 20 is, for example, 0.2 times to 1.0 times of H. If D1 is within this range, it is possible to obtain the pneumatic tire 1 having good side cut performance, effectively reducing air resistance, and having excellent traction performance at the same time.

[0042] <Second Embodiment> Next, an example of another embodiment, a pneumatic tire 1x, will be described with reference to FIGS. 5 to 6. In the following embodiments, the same components as those in the first embodiment are denoted by the same reference numerals as in the first embodiment, and the description thereof will be omitted. Further, in the following embodiments, the description of the same operational effects and modifications as those in the first embodiment will be omitted.

[0043] As shown in FIG. 5, in the present embodiment, unlike the first embodiment, the sidewall 3 does not have the side rib 20 between the tire maximum width position P and the buttress portion. On the other hand, also in the present embodiment, similar to the first embodiment, there is a recess 21x between the tire maximum width position P and the buttress portion. That is, the recess 21x is recessed with respect to the profile surface 3a of the sidewall 3.

[0044] The recess 21x has the same outer shape as that in the first embodiment in a plan view of the tire side surface. That is, the area of the recess 21 is 20% to 60% with respect to the area between the ground contact end E and the tire maximum width position P in a plan view of the tire side surface, similar to the first embodiment.

[0045] Next, the cross-sectional shape of the recess 21x will be described with reference to FIG. 6. FIG. 6 is a cross-sectional view showing a part of the cross-section taken along the line C-C in FIG. 5. The line C-C passes through the shoulder block 11 in the tread 2 and passes through the first recess 22x in the sidewall 3. Similar to the first embodiment, a step is formed at the boundary between the first recess 22x and the second recess 23x, and the first recess 22x is recessed more deeply than the second recess 23x.

[0046] As shown in FIG. 6, in the first recess 22x, the depth D2 of the recess 21 with respect to the profile surface 3a of the sidewall 3 becomes shallower from the outer side in the tire radial direction to the inner side in the tire radial direction. On the other hand, the profile of the bottom surface of the second recess 23x has the same shape as the second recess 23 in the first embodiment. That is, the second recess 23x has a first region 231, a second region 232, and a third region 233 such that the depth changes in the tire radial direction.

[0047] The maximum depth of the recess 21x with reference to the profile surface 3a of the sidewall 3 is, for example, 1 mm to 5 mm. That is, as described above, the first recess 22x, which is deeper than the second recess 23x, is deepest at the radially outer end of the tire diameter, and its depth is preferably 1 mm to 5 mm. If the maximum depth of the recess 21 is within this range, the effects of the present invention, which achieves both suppression of air resistance and improvement of traction performance, will become more prominent.

[0048] The radially inner end Q of the recess 21 is located radially outside the maximum tire width position P, and the distance L3 between the radially inner end Q of the recess 21 and the maximum tire width position P is 1% to 20% with respect to the distance L4 between the ground contact end E and the maximum tire width position P.

[0049] Regarding the pneumatic tire 1 (No. 1 to No. 6) according to the first embodiment and the tire of the comparative example (No. 7) in which the recess 21 was not formed in the pneumatic tire 1 according to the first embodiment, a simulation by the finite element method (FEM) was performed. The tires of No. 1 to No. 5 are provided with side ribs 20, recesses 21, and connecting portions 25 having the shapes shown in FIGS. 1 to 4. On the other hand, the tire of No. 6 has the same configuration as the tire of No. 2 except that it does not have the connecting portion 25. That is, in the tire of No. 6, the radially inner ends of the side rib 20 and the recess 21 coincide. Regarding the tires of No. 1 to No. 7, while changing the height H of the side rib 20, the maximum depth D1 of the recess 21, and the presence or absence of the continuous portion 25, the air resistance index, the traction index, and the ozone crack index were evaluated as described below. In addition, in the plan view of the tire side surface, the area of the recess 21 was 40% with respect to the area of the region from the ground contact end E to the maximum tire width position P. Also, the distance between the connecting portion 25 and the maximum tire width position P was 6% with respect to the distance between the ground contact end E and the maximum tire width position P.

[0050] [Evaluation of air resistance] For each test tire, the drag force (the force acting on the tire placed in the air flow and in the same direction as the flow) was measured, and the drag coefficient Cd was calculated from the following equation. The drag force was determined from the pressure difference before and after the tire by simulation. Cd = D / (1 / 2 ρU2S) In the equation, D is the generated drag force. ρ is the air density, which was set to 1.18415 [kg / m 3 . U is the representative speed, which is the relative speed between the tire and the air, and was set to 36.1 [m / s]. S is the representative area of the tire (frontal projected area).

[0051] [Evaluation of Traction Performance] Based on the single-wheel traction test "ASTM F1805" used in snow traction evaluation, the traction performance of each test tire was evaluated on muddy ground. Through this test, the longitudinal force (Fx) and the vertical load (Fz) of each test tire were obtained, and the forward traction index (μ = Fx / Fz) was obtained. The traction index (μ) of each test tire indicates the friction characteristics of the tire on the road surface where the test was conducted and is calculated as a relative value with respect to the value of the reference tire. The larger the value, the better the traction performance.

[0052] This test is performed by mounting each test tire and the reference tire on one test wheel of the test vehicle and driving the test course. The evaluation is also carried out based on the following standards. ASTM F1805 ASTM F377 ASTM D2487 ASTM D4318

[0053] The load and air pressure of the tire shall be the values applicable to light truck tires. Specifically, the test load is 425 kgf and the air pressure is 240 kPa.

[0054] [Evaluation of Ozone Crack Performance] Ozone was blown onto each test tire to evaluate the ozone cracking performance. Specifically, the test was conducted according to the following procedure. (1) Mount the test tire (275 / 60R20) on the specified rim and fill it with the test internal pressure (180 kPa). (2) Blow ozone with a concentration of 60 pphm onto the tire at 35 °C. (3) Adjust the air pressure every 24 hours, and while maintaining the test internal pressure, run at 420 rpm for 720 hours to check the occurrence status of ozone cracks. The larger the value of the ozone crack index, the better the ozone cracking performance.

[0055] The evaluation results of the pneumatic tires 1 of No. 1 to No. 7 are shown in Table 1. The evaluation results shown in Table 1 are relative values when the value of the No. 7 tire as a comparative example is set to 100.

[0056]

Table 1

[0057] Regarding the pneumatic tire 1x (No. 8 to No. 10) according to the second embodiment and the tire (No. 11) of the comparative example in which the recess 21 was not formed in the pneumatic tire 1x according to the second embodiment, a simulation by the finite element method (FEM) was performed. For the tires of No. 8 to No. 11, while changing the maximum depth of the recess, in the same manner as above, the air resistance index and the traction index were evaluated. In the plan view of the tire side surface, the area of the recess 21 was 40% with respect to the area of the region from the ground contact end E to the tire maximum width position P. Also, the distance between the inner end Q in the tire radial direction of the recess 21 and the tire maximum width position P was 6% with respect to the distance between the ground contact end E and the tire maximum width position P.

[0058] From the results in Table 1, it is understood that when the recess 21 is present, it is possible to effectively reduce air resistance while improving traction performance. In particular, when D1 / H is less than 1.7, ozone crack performance can also be further improved. Further, when the connecting portion 25 is present (No. 2), the coexistence of reducing air resistance and improving traction performance is remarkable compared to the case where the continuous portion 25 is not present (No. 6).

[0059]

Table 2

[0060] From the results in Table 2, it is understood that when the recess 21 is present, it is possible to effectively reduce air resistance while improving traction performance. In particular, when the maximum depth of the recess 21 is in the range of 1 mm to 5 mm, this effect is particularly remarkable.

[0061] As described above, according to the pneumatic tire 1 having the recesses 21 periodically and repeatedly arranged in the tire circumferential direction between the tire maximum width position P and the buttress portion, it is possible to effectively reduce air resistance while improving traction performance. By forming the recesses 21, it is possible to create an air flow along the surface of the sidewall 3, thereby greatly reducing air resistance. Further, due to the recesses 21, mud and the like are easily discharged in muddy areas and the like, so that the traction performance is improved.

[0062] According to the pneumatic tires 1 and 1x, it is possible to reduce air resistance while ensuring traction performance equal to or better than that of the conventional tires. The pneumatic tire 1 is particularly suitable for tires for light trucks. In particular, since the pneumatic tire 1 according to the first embodiment has the side rib 20, it has better side protection performance than the pneumatic tire 1x according to the second embodiment.

Explanation of Reference Numerals

[0063] 1,1x Pneumatic tire with air, 2 Tread, 2a, 2b Shoulder blocks, 2c, 2d Grooves, 3 Sidewall, 3a Profile surface, 4 Bead, 10, 11 Shoulder blocks, 10a, 11a Side surfaces, 12, 13 Grooves, 20 Side rib, 21, 21x Recesses, 22, 22x First recesses, 23, 23x Second recesses, 231 First region, 232 Second region, 233 Third region, 24 Boundary, 25 Continuity, E Ground contact end, P Tire maximum width position

Claims

1. A pneumatic tire comprising a tread, a sidewall, and a bead, wherein the sidewall has recesses periodically and repeatedly arranged in the circumferential direction of the tire between the maximum tire width position and the buttress portion.

2. The sidewall has a side rib between the maximum tire width position and the buttress portion, and the recess is recessed with respect to the outer surface of the side rib. The pneumatic tire according to claim 1.

3. The height H of the side rib with reference to the profile surface of the sidewall is 1 mm to 15 mm. The pneumatic tire according to claim 2.

4. The maximum depth of the recess with reference to the outer surface of the side rib is 0.2 times to 1.0 times of the H. The pneumatic tire according to claim 2.

5. The side rib has an annular continuous portion continuous in the circumferential direction of the tire at the radially inner end of the tire, and the distance between the continuous portion and the maximum tire width position is 1% to 20% with respect to the distance between the ground contact end and the maximum tire width position. The pneumatic tire according to claim 2.

6. In a plan view of the side surface, the area of the recess is 20% to 60% with respect to the area of the region from the ground contact end to the maximum tire width position. The pneumatic tire according to claim 1.

7. The sidewall does not have a side rib between the maximum tire width position and the buttress portion, and the recess is recessed with respect to the profile surface of the sidewall. The pneumatic tire according to claim 1.

8. The maximum depth of the recess with reference to the profile surface of the sidewall is 1 mm to 5 mm. The pneumatic tire according to claim 7.

9. The recess has a portion where the depth of the recess with reference to the profile surface of the sidewall becomes shallower from the radially outer side to the radially inner side of the tire. The pneumatic tire according to claim 7.

10. The area of the recess is 20% to 60% with respect to the area between the ground contact end and the maximum tire width position in a plan view of the side surface. The pneumatic tire according to claim 7.

11. The radially inner end of the recess is located radially outside the maximum tire width position. The distance between the inner end of the concave portion in the tire radial direction and the tire maximum width position is 1% to 20% with respect to the distance between the grounding end and the tire maximum width position, the pneumatic tire according to claim 7.

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