TIRES

Abstract

Pneumatic tires (1), comprising: two main circumferential grooves (22A, 22B) extending in the circumferential direction of the tire and arranged side by side in the width direction of the tire; and a first bridge section (20C) defined by the two main circumferential grooves (22A, 22B), wherein the two main circumferential grooves (22A, 22B) comprise an inner main circumferential groove (22A) which is closest to an equatorial plane of the tire, and an outer main circumferential groove (22B) which is provided on an outer side in the tire width direction with respect to the inner main circumferential groove (22A), wherein the first rib section (20C) comprises a recess section (23Ki, 23Ko) extending in the tire width direction and connected to the main circumferential groove (22A, 22B), and a flat groove section (23Gi, 23Go) connected to the recess section (23Ki, 23Ko) and ending blindly in the first rib section (20C), and wherein the height of the recess section (23Ki, 23Ko) decreases continuously towards the associated main circumferential groove (22A, 22B), wherein the ratio of the depth (DG) of the flat groove section (23Gi, 23Go) to the depth (DK) of the associated recess section (23Ki, 23Ko) is greater than 0 and equal to or less than 0.2.

Description

Technical field

[0001] The present invention relates to a pneumatic tire. State of the art

[0002] Road and off-road tires designed for driving on rough and paved roads are well-known. For such tires, improvements in resistance to uneven wear, as well as improvements in dry and wet performance, are required. Generally, improved resistance to uneven wear is achieved by increasing the contact patch, and improved drainage is achieved by increasing the groove area, both of which are inherently conflicting.

[0003] JP 2013 - 100 063 A discloses a technology for preventing an abrupt decrease in wet performance during wear, while improving the resistance performance of a shoulder block to uneven wear.

[0004] EP 2 281 698 A1 describes a pneumatic tire with improved wet grip and reduced road noise. The pneumatic tire comprises a tread pattern with five ribs separated by circumferential grooves. Some of the ribs contain grooves running obliquely to the circumferential direction, each groove consisting of several groove segments, one of which terminates blindly within a rib.

[0005] EP 3 135 505 A1 describes a pneumatic tire with improved mileage on dry and snowy surfaces. The pneumatic tire has a tread pattern with several circumferential grooves. Adjacent to these grooves are several short grooves that terminate blindly in a lug of the tread pattern and run obliquely to the circumferential direction.

[0006] JP H02-169 306 A describes a pneumatic tire with improved rolling and sliding properties. The tire has a tread pattern with four circumferential grooves. At regular intervals, blind-ending groove sections branch off from these grooves, extending across the width of the tire. These blind-ending groove sections have varying groove depths along their length. Brief description of the invention: Technical problem

[0007] The technology disclosed in JP 2013 - 100 063 A relates to a shoulder block, and there is room for improvement in improving resistance performance to uneven wear and in improving drainage performance throughout the tread section.

[0008] In light of the foregoing, it is an object of the present invention to provide a pneumatic tire with improved resistance to uneven wear and improved drainage performance. Solution to the problem

[0009] To solve the problems and accomplish the task described above, a pneumatic tire according to one aspect of the present invention includes: two main circumferential grooves extending in the circumferential direction of the tire and arranged side by side in the width direction of the tire;and a first rib section defined by the two main circumferential grooves, wherein the two main circumferential grooves include an inner main circumferential groove closest to an equatorial plane of the tire, and an outer main circumferential groove provided in the tire width direction with respect to the outer side of the inner main circumferential groove, wherein the first rib section includes a recess section extending in the tire width direction and connected to the main circumferential groove, and a shallow groove section connected to the recess section and ending blindly in the first rib section, and wherein the height of the recess section decreases continuously towards the main circumferential groove to which it is connected. The ratio of the depth of the shallow groove section to the depth of the recess section to which it is connected is greater than 0 and equal to or less than 0.2.

[0010] Preferably, the recessed section decreases continuously from a height corresponding to 5% tire wear to a height corresponding to 70% tire wear. Preferably, the ratio of a depth of the

[0011] The depth of the recessed section is greater than 0 and less than 0.80, with a groove depth of 0.50 or more and 0.80 or less, respectively. According to the invention, the ratio of the depth of the shallow groove section to the depth of the associated recessed section is greater than 0 and equal to or less than 0.2.

[0012] Preferably, the ratio of a length in the tire width direction of a flat section of a bottom section of the recess section to a length in the tire width direction of the flat groove section is greater than 0 and equal to or less than 0.5.

[0013] Preferably, the angle of the recess section with respect to a normal of a running surface contact surface is greater than 0° and equal to or less than 45°.

[0014] Preferably, the recess section includes an inner recess section extending in the tire width direction and connected to the inner main circumferential groove, and an outer recess section extending in the tire width direction and connected to the outer main circumferential groove, and the flat groove section includes an inner flat groove section connected to the inner recess section and ending blindly in the first rib section, and an outer flat groove section connected to the outer recess section and ending blindly in the first rib section.

[0015] Preferably, in the outer recess section and the outer flat groove section connected to the outer recess section, there is a ratio S1 / S2 of a projection surface S1 of the outer flat groove section to a projection surface S2 of the outer recess section. 0.1≤S1 / S2≤0.5.

[0016] Preferably, the pneumatic tire further includes: a plurality of lateral direction grooves extending in the tire width direction between the inner main circumferential groove and the outer main circumferential groove, and a block defined by the inner main circumferential groove, the outer main circumferential groove and the plurality of lateral direction grooves, and a ratio S2 / S of the projection area S2 of the outer recess section to a ground contact area S of the block is 0 < S2 / S ≤ 0.1.

[0017] Preferably, in the inner recess section and the inner flat groove section connected to the inner recess section, the ratio S3 / S4 of a projection surface S3 of the inner flat groove section to a projection surface S4 of the inner recess section is 0.5≤S3 / S4≤0.9.

[0018] Preferably, the pneumatic tire further includes: a plurality of lateral direction grooves extending in the tire width direction between the inner main circumferential groove and the outer main circumferential groove, and a block defined by the inner main circumferential groove, the outer main circumferential groove and the plurality of lateral direction grooves, and a ratio S4 / S of a projection area S4 of the inner recess section to a ground contact area S of the block is 0 < S4 / S ≤ 0.1.

[0019] Preferably, the ratio d11 / D of a distance d11 in the tire width direction from an end section of the inner recess section near the inner main circumferential groove to a blind-ending end section of the inner flat groove section connected to the inner recess section, to a distance D in the tire width direction between an end section of the inner recess section near the inner main circumferential groove and an end section of the outer recess section near the outer main circumferential groove is 0.1 or more and 0.3 or less, and the ratio d12 / D of a distance d12 in the tire width direction from an end section of the outer recess section near the outer main circumferential groove to a blind-ending end section of the outer flat groove section connected to the outer recess section is 0.1 or more and 0.4 or less.

[0020] Preferably, a plurality of inner recess sections and a plurality of inner flat groove sections are arranged in the circumferential direction of the tire, a plurality of outer recess sections and a plurality of outer flat groove sections are arranged in the circumferential direction of the tire, a ratio of a misalignment amount of an arrangement of the inner recess sections to a pitch spacing length of an arrangement of the outer recess sections is 0.1 or more and 0.5 or less, and a ratio of a misalignment amount of an arrangement of the inner flat groove sections to a pitch spacing length of an arrangement of the outer flat groove sections is 0.1 or more and 0.5 or less.

[0021] Preferably, the pneumatic tire further includes: a second rib section provided on the outer side in the tire width direction with respect to the main circumferential groove; a second recess section provided in the second rib section and ending blindly in the second rib section; a third rib section provided such that the inner main circumferential groove lies between them; a third recess section provided in the third rib section, extending in the tire width direction and connected to the inner main circumferential groove; and a flat groove section connected to the third recess section and ending blindly in the third rib section. Advantageous effects of the invention

[0022] The pneumatic tire according to an embodiment of the present invention can improve resistance to uneven wear and improve drainage performance throughout the entire tread area. Brief description of the drawings Fig. Figure 1 is a meridian cross-sectional view of a pneumatic tire according to the present embodiment. Fig. Figure 2 is a top view illustrating a tread surface of the pneumatic tire according to the present embodiment. Fig. Figure 3 is a top view illustrating a detailed configuration of an inner major circumferential groove. Fig. Figure 4 is a cross-sectional view along line AA in Fig. 3. Fig. Figure 5 is a cross-sectional view illustrating a detailed configuration of a recess section and a flat groove section. Fig.Figure 6 is a top view illustrating a detailed configuration of an outer major circumferential groove. Fig. Figure 7 is a cross-sectional view along line CC in Fig. 6. Fig. Figure 8 is an enlarged view of the block in Fig. 2. Fig. Figure 9 is an enlarged view of an outer recess section and an outer flat groove section in Fig. 8. Fig. Figure 10 is an enlarged view of an inner recess section and an inner flat groove section in Fig. 8. Description of embodiments

[0023] Embodiments of the present invention are described in detail below with reference to the drawings. However, the present invention is not limited to these embodiments. Components of the embodiment include elements that are essentially identical or that can be substituted or easily devised by a person skilled in the art. Furthermore, the majority of the modified examples described in the embodiment can be combined as needed, within the scope obvious to a person skilled in the art. In addition, some components may not be used in certain embodiments. pneumatic tires

[0024] Fig. Figure 1 is a meridian cross-sectional view of a pneumatic tire 1 according to the present embodiment. Fig. Figure 2 is a top view of a tread surface of the pneumatic tire 1 according to the present embodiment.

[0025] Herein, "tire radial direction" refers to the direction perpendicular to the axis of rotation (not illustrated) of a pneumatic tire 1. "Inside in tire radial direction" refers to a side towards the axis of rotation in the tire radial direction. "Outside in tire radial direction" refers to a side away from the axis of rotation in the tire radial direction. "Tire circumferential direction" refers to the circumferential direction, with the central axis being the axis of rotation. "Tire width direction" also refers to a direction parallel to the axis of rotation. "Inside in tire width direction" refers to a side towards an equatorial plane of the tire (tire equator line) CL in the tire width direction. "Outside in tire width direction" refers to a side away from the equatorial plane CL of the tire in the tire width direction.“Tire equatorial plane CL” refers to a plane perpendicular to the axis of rotation of the pneumatic tire 1 and passing through the center of a tire width of the pneumatic tire 1. “Tire width” is the width in the tire width direction between components located at the outer edges in the tire width direction, or in other words, the distance between the components furthest from the tire equatorial plane CL in the tire width direction. “Tire equator line” refers to the line in the circumferential direction of the pneumatic tire 1 that lies on the tire equatorial plane CL. In the present embodiment, the tire equator line and the tire equatorial plane are designated with the same reference numeral CL.

[0026] As in Fig.As illustrated in Figure 1, the pneumatic tire 1 of the present embodiment includes a tread section 2, shoulder sections 3 on both sides of the tread section 2 that are outer in the direction of the tire width, and sidewall sections 4 and bead sections 5, which extend continuously from the shoulder sections 3 in this order. The pneumatic tire 1 also includes a carcass layer 6 and a belt layer 7.

[0027] The tread section 2 is made of a rubber material (tread rubber) and is exposed on the outermost side of the pneumatic tire 1 in the tire radial direction, its surface forming the contour of the pneumatic tire 1. A tread surface 21 is formed on an outer circumferential surface of the tread section 2, in other words, on a road contact surface that comes into contact with a road surface when driving. A plurality (three in the present embodiment) of main circumferential grooves 22A, 22B, extending in the tire circumferential direction, are provided in the tread surface 21. A plurality (four in the present embodiment) of rib sections 20C, 20S, defined by the plurality of main circumferential grooves 22A, 22B, extending in the tire circumferential direction and arranged in the tire width direction, are provided in the tread surface 21.

[0028] Furthermore, as in Fig.Figure 2 illustrates the tread surface 21, main circumferential grooves 22A, 22B extending in the tire's circumferential direction, and a lug groove 24 extending in a direction that intersects the main circumferential grooves 22A, 22B. The main circumferential groove 22A is the inner main circumferential groove closest to the tire's equator line CL. The main circumferential groove 22B is the second closest main circumferential groove to the tire's equator line CL. The main circumferential groove 22B is an outer main circumferential groove provided on the outer side in the tire's width direction with respect to the main circumferential groove 22A, which is the inner main circumferential groove. No other main circumferential grooves are provided between the main circumferential groove 22A and the main circumferential groove 22B. “Main grooves” refers to a groove on which a wear indicator must be provided, as specified by JATMA.Furthermore, the lug grooves are transverse grooves that extend in the direction of the tire's width and open when the tire comes into contact with the ground, thus functioning as grooves. It should be noted that the sipes described below are incisions formed in the tread contact surface and differ from lug grooves in that the sipes are closed when the tire is in contact with the ground.

[0029] In Fig. 1 and Fig.2 The ground contact edge T of the tire is defined as the position of maximum width in the tire axial direction of the contact surface between the tire and a flat plate when the tire is mounted on a specified rim, inflated to the specified internal pressure, placed vertically on the flat plate in a static state, and loaded with a load corresponding to the specified load. The rib section 20S includes lug grooves 30 on the outer edge section in the tire width direction. The lug grooves 30 are provided in the rib sections 20S at a predetermined pitch in the tire circumferential direction. The end section of the lug groove 30 on the side closer to the equatorial plane CL of the tire terminates blindly in the rib section 20S.The end section of the lug groove 30 on the side that is further away from the equatorial plane CL of the tire extends beyond the ground contact edge T of the tire in the direction of the tire width and opens towards the shoulder section 3.

[0030] In Fig.The shoulder sections 3 are sections of the tread section 2, arranged on both outer sides in the tire width direction. Additionally, the sidewall sections 4 are exposed at the outermost sides of the pneumatic tire 1 in the tire width direction. The bead sections 5 each enclose a tire bead core 51 and a bead filler 52. The tire bead core 51 is formed by winding a tire bead wire, which is a steel wire, into a ring shape. The bead filler 52 is a rubber material arranged in a cavity formed when an end section of the carcass layer 6 is folded back towards the outer side in the tire width direction at the position of the bead core 51.

[0031] The end sections of the carcass layer 6, in the tire width direction, are folded over the pair of bead cores 51 from an inside to an outside, and the carcass layer 6 is stretched in a torus shape in the tire circumference direction to form the tire skeleton. The carcass layer 6 is made of carcass cord threads (not illustrated) coated with rubber, arranged side by side at an angle to the tire circumference along the tire meridian direction. The carcass cord threads are made of steel or organic fibers (polyester, rayon, nylon, or the like).

[0032] The belt layer 7 has a multi-layer structure, in which, for example, four layers of belts 71, 72, 73, 74 are stacked, and is arranged in the tread section 2 on the outer side (in the tire radial direction), which is the outer circumference, of the carcass layer 6, so that it covers the carcass layer 6 in the tire circumferential direction. The belts 71, 72, 73, 74 are made of cord threads (not illustrated) coated with coating rubber, which are arranged side by side at a predetermined angle with respect to the tire circumferential direction. The cord threads are made of steel or organic fibers (polyester, rayon, nylon, or the like).

[0033] Groove depth is the maximum distance from the tread contact surface to the groove bottom and is measured when the tire is mounted on a specified rim, inflated to the specified internal pressure, and in an unloaded state. Additionally, in configurations where the grooves include an uneven section or sipes on the groove bottom, the groove depth is measured excluding these sections.

[0034] "Specified rim" refers to a "standard rim" as defined by JATMA, a "design rim" as defined by TRA, or a "measuring rim" as defined by ETRTO. "Specified internal pressure" refers to a "maximum air pressure" as defined by JATMA, the maximum value in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" as defined by TRA, or "INFLATION PRESSURES" as defined by ETRTO. Furthermore, “specified load” refers to a “maximum load capacity” as defined by JATMA, the maximum value in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” as defined by TRA, or “LOAD CAPACITY” as defined by ETRTO. Bridge sections

[0035] As in Fig. As illustrated in Figure 2, in this example, blocks BK in the rib section 20C of tread section 2 are defined by the main circumferential grooves 22A, 22B, and the lug grooves 24 extending in the tire width direction. Instead of lug grooves 24, tread section 2 may have sipes (not illustrated) extending in the tire width direction. In this case, blocks BK are defined by the main circumferential grooves 22A, the main circumferential grooves 22B, and their sipes. In other words, tread section 2 of this example has blocks BK defined by two main circumferential grooves extending in the tire circumference direction and width-direction grooves (lug grooves 24 or sipes) extending in the tire width direction.

[0036] The blocks BK are arranged side by side in the tire's circumferential direction on both sides of the tire's equator line CL in the tire's width direction. Therefore, tread section 2 of this example has rib sections in which the blocks BK are arranged side by side in the tire's circumferential direction.

[0037] Block BK has a recessed section 23Ki on the edge of the side closer to the tire equator line CL. A shallow grooved section 23Gi is connected to the recessed section 23Ki. Block BK also has a recessed section 23Ko on the edge of the side farther from the tire equator line CL. A shallow grooved section 23Go is connected to the recessed section 23Ko. By providing the recessed section 23Ki and the shallow grooved section 23Gi, and the recessed section 23Ko and the shallow grooved section 23Go in the edge of block BK, resistance to uneven wear and drainage performance can be improved.

[0038] It should be noted that instead of the blocks BK, which are arranged side by side in the circumferential direction of the tire, rib-shaped rib sections, which are defined by the main circumferential groove 22A and the main circumferential groove 22B and are provided continuously in the circumferential direction of the tire, may be provided in the tread section 2 and the recess section 23Ki, the flat groove section 23Gi, the recess section 23Ko and the flat groove section 23Go may be provided in the edge of the rib section. Inner main circumferential groove

[0039] Fig. Figure 3 is a top view illustrating a detailed configuration of the main circumferential groove 22A, which is an inner main circumferential groove. Fig. Figure 3 is an enlarged view of area 26 in Fig. 2. As in Fig.As illustrated in Figure 3, the main circumferential groove 22A extends in the tire circumferential direction along the tire equator line CL. Both sides of the main circumferential groove 22A are rib sections 20C.

[0040] In this example, the main circumferential groove 22A has a zigzag shape that curves on one side and on the other side of the tire equator line CL, with the tire equator line CL as its centerline. The main circumferential groove 22A is connected to the lug groove 24 in the zigzag-shaped curved section. The web section 20C, which faces the connecting section between the main circumferential groove 22A and the lug groove 24, includes a recess section 23Ki, which is connected to the main circumferential groove 22A, and a shallow groove section 23Gi, which is connected to the recess section 23Ki and terminates blindly within the web section 20C. Note that a dashed line H2 represents an imaginary line of the main circumferential groove 22A when viewed from a top view.

[0041] The main circumferential groove 22A has a stepped section 222 between a tread contact surface 220 and a groove base section 221. The stepped section 222 extends in the tire circumferential direction, with the exception of the connecting sections of the main circumferential grooves 22A and the lug grooves 24.

[0042] Fig. Figure 4 is a diagram illustrating the structure of the main circumferential groove 22A. Fig. Figure 4 is a cross-sectional view along line AA in Fig. 3. As in Fig. As illustrated in Figure 4, the step section 222 is provided in the main circumferential groove 22A between the tread contact surface 220 and the groove bottom section 221. It should be noted that in the groove wall, from the tread contact surface 220 to the step section 222, the angle θ1 with respect to the normal of the tread contact surface 220 is, for example, 18°. Recessed sections and flat grooved sections

[0043] Fig. Figure 5 is a cross-sectional view illustrating a detailed configuration of the recess section and the flat groove section. Fig. Figure 5 is a cross-sectional view along line BB in Fig. 3. Here, the recess section 23Ki and the recess section 23Ko are referred to together as the recess section 23K, and the shallow groove section 23Gi and the shallow groove section 23Go are referred to together as the shallow groove section 23G.

[0044] In Fig. 5 The recess section 23K is provided in the edge section of the main circumferential groove 22A. The recess section 23K extends in the tire width direction and is connected to the main circumferential groove 22A. A dashed line H in Fig.Figure 5 illustrates the groove wall of the main circumferential groove 22A. The flat groove section 23G is connected to the recess section 23K and ends blindly in the web section 20C, which is a first web section.

[0045] Due to the flat groove section 23G, which extends from and is connected to the recess section 23K, the edge component is increased and the drainage properties are improved. Furthermore, by arranging the flat groove section 23G instead of lamellae, block stiffness can be maintained, and resistance to uneven wear and drainage performance can be achieved in a compatible manner. It should be noted that the flat groove section 23G is a groove that, for example, has a groove depth of 1 mm and a groove width of 0.5 mm or more and 3.5 mm or less.

[0046] The height of the recess section 23K decreases continuously towards the associated main circumferential groove 22A. More precisely, the height of the recess section 23K changes continuously from an end section KT1 on the outside in the tire radial direction to an end section KT2 on the inside in the tire radial direction, instead of changing in steps. The bottom section of the recess section 23K near the end section KT2 is flat. In this flat section, the recess section 23K and the groove wall of the main circumferential groove 22A coincide.

[0047] The position of end section KT1 on the outer side of the tire (in the radial direction) with respect to recess section 23K corresponds to the position of end section GT1 of the shallow groove section 23G near recess section 23K. The position of end section GT1 of the shallow groove section 23G near recess section 23K is at a height corresponding to 5% tire wear in the radial direction. The position of end section KT2 on the inner side of the tire (in the radial direction) with respect to recess section 23K corresponds to the position of end section 222 of the step section 222 of the main circumferential groove 22A on the side closer to the groove bottom section 221.The position of the end section of the stepped section 222 of the main circumferential groove 22A on the side closer to the groove base section 221 is at a height corresponding to 70% tire wear in the radial direction. Thus, although the height of the recess section 23K only changes when the tire wear reaches 5%, its height decreases continuously as the tire wear changes by 5% or less until it reaches 70%. That is, the height of the recess section 23K decreases continuously from a height corresponding to 5% tire wear to a height corresponding to 70% tire wear.

[0048] The ratio DK / DB of the depth DK of the recess section 23K to the groove depth DB of the main circumferential groove 22A, to which the recess section 23K is connected, is preferably 0.50 or more and 0.80 or less. If the DK / DB ratio is within this range, the resistance to uneven wear and the drainage performance are improved.

[0049] The angle α of the recess section 23K with respect to the normal of the running surface contact surface 220 is preferably greater than 0° and equal to or less than 45°. If the angle is within this range, the resistance to uneven wear is improved. The angle α is more preferably 20° or more and 40° or less.

[0050] According to the invention, the ratio DG / DK of the depth DG of the flat groove section 23G to the depth DK of the recess section 23K to which the flat groove section 23G is connected is greater than 0 and equal to or less than 0.2. When the DG / DK ratio is within this range, the resistance to uneven wear and the drainage performance are improved. The DG / DK ratio is more preferably 0.02 or greater and 0.18 or less.

[0051] The ratio LK / LG of the length LK in the tire width direction of the flat section of the bottom section of the recess section 23K to the length LG in the tire width direction of the flat groove section 23G is greater than 0 and equal to or less than 0.5. If the LK / LG ratio is within this range, the resistance to uneven wear is improved. The LK / LG ratio is more preferably 0.05 or more and 0.50 or less, and further preferably 0.1 or more and 0.3 or less.

[0052] It should be noted that, although the recess section 23K associated with the main circumferential groove 22A has been described, a similar configuration is applied to the recess section 23K and the flat groove section 23G associated with the main circumferential groove 22B. Outer main circumferential grooves

[0053] Fig.Figure 6 is a top view illustrating a detailed configuration of the major circumferential groove 22B, which is an outer major circumferential groove. Fig. Figure 6 is an enlarged view of area 27 in Fig. 2. As in Fig. As illustrated in Figure 6, the main circumferential groove 22B extends in the direction of the tire's circumference. Beneath the rib sections on both sides of the main circumferential groove 22B, rib section 20C is located on the side closer to the tire's equator line CL, and rib section 20S is located on the side farther from the tire's equator line CL.

[0054] In this example, the main circumferential groove 22B has a zigzag shape, curving on the side closer to the tire equator line CL and on the side farther from the tire equator line CL. The main circumferential groove 22B is connected to the lug groove 24 or the recess section 23Ko in the zigzag-shaped curved section.

[0055] The web section 20S, which faces the connecting section between the main circumferential groove 22B and the lug groove 24, has a recess section 25. The recess section 25 terminates blindly in the web section 20S.

[0056] The web section 20C includes the recess section 23Ko, which is connected to the main circumferential groove 22B, and the shallow groove section 23Go, which is connected to the recess section 23Ko and terminates blindly in the web section 20C. Note that a dashed line H3 represents an imaginary line of the main circumferential groove 22B when viewed from a top view.

[0057] The main circumferential groove 22B has the stepped section 222 between the tread contact surface 220 and the groove base section 221. The stepped section 222 extends in the tire circumferential direction, with the exception of the connecting sections of the main circumferential grooves 22B and the lug grooves 24.

[0058] Fig. Figure 7 is a diagram illustrating the structure of the major circumferential groove 22B. Fig. Figure 7 is a cross-sectional view along line CC in Fig. 6. As in Fig. As illustrated in Figure 7, a step section 222 is provided in the main circumferential groove 22B between the tread contact surface 220 and the groove bottom section 221. It should be noted that in the groove wall, from the tread contact surface 220 to the step section 222, the angle θ2 with respect to the normal of the tread contact surface 220 is, for example, 15°. Width of the web section and length of the recess section and the flat groove section

[0059] Fig. Figure 8 is an enlarged view of block BK in Fig. 2. In Fig. 8. The distance in the tire width direction between the end section of the inner recess section 23Ki near the inner main circumferential groove 22A and the end section of the outer recess section 23Ko near the outer main circumferential groove 22B is defined as the distance D. The distance D is identical to the width in the tire width direction of the rib section 20C, which is the first rib section.

[0060] The distance in the tire width direction from the end section of the inner recess section 23Ki near the inner main circumferential groove 22A to the blind-ending end section of the inner flat groove section 23Gi, which is connected to the inner recess section 23Ki, is defined as the distance d11. The distance d11 is the length in the tire width direction of the inner recess section 23Ki and the inner flat groove section 23Gi. In this case, the ratio d1 / D of the distance d11 to the distance D is preferably 0.1 or more and 0.3 or less. When the ratio d11 / D is 0.1 or more and 0.3 or less, the resistance to uneven wear is improved. The ratio d11 / D is more preferably 0.2.

[0061] Furthermore, the distance in the tire width direction from the end section of the outer recess section 23Ko near the outer main circumferential groove 22B to the blind-ending end section of the outer flat groove section 23Go, which is connected to the outer recess section 23Ko, is defined as the distance d12. The distance d12 is the length in the tire width direction of the outer recess section 23Ko and the outer flat groove section 23Go. In this case, the ratio d12 / D of the distance d12 to the distance D is preferably 0.1 or more and 0.4 or less. When the ratio d12 / D is 0.1 or more and 0.4 or less, the resistance to uneven wear is improved. The ratio d12 / D is more preferably 0.3. Ground contact surface of the block and projection surface of the recess section

[0062] Fig.9 is an enlarged view showing the outer recess section 23Ko and the outer flat groove section 23Go in Fig. 8 illustrates this. Fig. 9 is a dashed line H3, an imaginary line of the major circumferential groove 22B when the major circumferential groove 22B is viewed in a top view. Fig. 9 The projection surface of the outer recess section 23Ko is defined as S2. Furthermore, the projection surface of the outer flat groove section 23Go, which is connected to the outer recess section 23Ko, is defined as S1. The projection surface is a surface of the tread surface 21 projected from the outside in the tire radial direction to the inside in the tire radial direction.

[0063] In this case, the ratio S1 / S2 of the projection area S1 to the projection area S2 is preferably 0.1 ≤ S1 / S2 ≤ 0.5. More preferably, it is 0.15 ≤ S1 / S2 ≤ 0.3. If the ratio S1 / S2 is less than 0.1, the drainage properties decrease, which is not preferred. If the ratio S1 / S2 is greater than 0.5, the soil contact area decreases and the resistance to uneven wear decreases, which is not preferred.

[0064] Furthermore, the ratio S2 / S of the projection area S2 of the in Fig. 9 illustrated outer recess section 23Ko to the ground contact surface S of the in Fig. For blocks BK 8, preferably 0 < S2 / S ≤ 0.1. More preferably 0.005 ≤ S2 / S ≤ 0.100. If the ratio S2 / S is greater than 0.100, the ground contact area of ​​block BK decreases, and the resistance to uneven wear decreases, which is not preferred.

[0065] The “ground contact area S” is the area of ​​a region in the tire width direction and in the tire circumference direction with which the tread surface of block BK comes into contact when the pneumatic tire 1 is mounted on a regular rim, inflated to a regular internal pressure and loaded with 70% of a regular load.

[0066] Fig. Figure 10 is an enlarged view showing the inner recess section 23Ki and the inner flat groove section 23Gi in Fig. 8 illustrates this. Fig. 10 is a dashed line H2, an imaginary line of the main circumferential groove 22A when the main circumferential groove 22A is viewed in a top view. Fig.In section 10, the projection area of ​​the inner recess section 23Ki is defined as S4. The projection area of ​​the inner flat groove section 23Gi, which is connected to the inner recess section 23Ki, is defined as S3. In this case, the ratio S3 / S4 of the projection area S3 to the projection area S4 is preferably 0.5 ≤ S3 / S4 ≤ 0.9. More preferably, it is 0.65 ≤ S3 / S4 ≤ 0.80. If the ratio S3 / S4 is less than 0.5, the drainage properties decrease, which is not preferred. If the ratio S3 / S4 is greater than 0.9, the soil contact area decreases and the resistance to uneven wear decreases, which is not preferred.

[0067] Furthermore, the ratio S4 / S of the projection area S4 of the in Fig. 10 illustrated inner recess section 23Ki to the ground contact surface S of the in Fig.In the 8 illustrated blocks BK, preferably 0 < S4 / S ≤ 0.1. More preferably 0.005 ≤ S4 / S ≤ 0.100. If the ratio of the projection area of ​​the inner recess section 23Ki to the ground contact area S of block BK is greater than 0.100, the ground contact area of ​​block BK decreases and the resistance to uneven wear decreases, which is not preferred.

[0068] Misalignment amount of the arrangement relative to the division length of the arrangement. Considering again... Fig. 2, a plurality of inner recess sections 23Ki and a plurality of inner flat groove sections 23Gi are arranged in the circumferential direction of the tire. In addition, a plurality of outer recess sections 23Ko and a plurality of outer flat groove sections 23Go are arranged in the circumferential direction of the tire.

[0069] The ratio of the misalignment amount PK of the arrangement of the inner recess sections 23Ki to the pitch distance PB1 of the arrangement of the outer recess sections 23Ko is preferably 0.1 or more and 0.5 or less. Furthermore, the ratio of the misalignment amount PG of the arrangement of the inner flat groove sections 23Gi to the pitch distance PB2 of the arrangement of the outer flat groove sections 23Go is preferably 0.1 or more and 0.5 or less. By optimizing the arrangement of the inner recess sections 23Ki and the outer recess sections 23Ko, and by optimizing the arrangement of the inner flat groove sections 23Gi and the outer flat groove sections 23Go, the resistance to uneven wear is improved. Configuration of adjacent bridge sections

[0070] Furthermore, in Fig.2. Focusing on the rib section 20C, which is a first rib section (20-1), the tread section 2 includes the rib section 20S, which is a second rib section (20-2), provided on the outside in the tire width direction of the outer main circumferential groove 22B, and the recess section 25, which is a second recess section provided in the rib section 20S, which is the second rib section (20-2) and terminates blindly in the rib section 20S. By providing the recess section 25 on the outside in the tire width direction of the outer main circumferential groove 22B, the edge component is increased and the drainage properties are improved.

[0071] Furthermore, when focusing on the rib section 20C, which is the first rib section (20-1), the tread section 2 includes the rib section 20C, which is a third rib section (20-3) provided such that the inner main circumferential groove 22A is located between them, the recess section 23Ki, which is a third recess section provided in the rib section 20C and extends in the tire width direction and is connected to the inner main circumferential groove 22A, and the flat groove section 23G1, which is connected to the recess section 23Ki and terminates blindly in the rib section 20C, which is the third rib section (20-3).By providing the recessed section 23Ki and the flat grooved section 23Gi in each of the web sections 20C, which are provided on both sides such that the inner main circumferential groove 22A lies between them, the edge component is increased and the drainage properties are improved. Examples

[0072] In the examples, performance tests regarding drainage performance (wet performance and resistance to uneven wear) were carried out on a variety of pneumatic tire types in different conditions (see Tables 1 to 4). For the performance tests, pneumatic tires (heavy-duty pneumatic tires) with a tire size of 11R22.5 were mounted on specified rims, inflated to a specified air pressure, and installed on a drive shaft of a test vehicle (2D semi-trailer truck).

[0073] To assess drainage performance, the distance traveled by the test vehicle was measured until it came to a complete stop on a wet road surface with a water depth of 1 mm, after the brakes were applied from a vehicle speed of 40 km / h. The reciprocals of the measured braking distances are expressed as index values ​​and evaluated as a reference value (100) based on the results of the prior art example. In this evaluation, higher index values ​​indicate better drainage performance.

[0074] To assess resistance to uneven wear, a rim on which pneumatic tire 1 is mounted is attached to the drive shaft of the test vehicle, and the degree of sawtooth wear after 5 million km of driving is measured by the market surveillance device. The measurement results are expressed as index values ​​and evaluated using the results of pneumatic tire 1 as a reference (100) for the prior art example. In this evaluation, higher index values ​​indicate better resistance to uneven wear.

[0075] The pneumatic tire of the prior art example in Table 1 includes the recess section 23K, but does not include the shallow groove section 23G, the height of the recess section changes in steps, and the ratio DK / DB of the depth of the recess section to the groove depth of the main circumferential groove is 0.4.

[0076] As can be seen from the test results in Tables 1 to 4, the pneumatic tires of the examples exhibit improved drainage performance and resistance to uneven wear. [Table 1-I] Example of the state of the art Example 1 (State of the Art) Example 2 (State of the Art) Example 3 (State of the Art) Example 4 (State of the Art) Presence / absence of the recess section Yes Yes Yes Yes Yes Presence / absence of the flat groove section No Yes Yes Yes Yes Height change of the recess section Step-like Ongoing Ongoing Ongoing Ongoing DK / DB ratio 0,4 0,4 0,4 0,4 0,4 DG / DK relationship 0,0 0,4 0,4 0,4 0,4 ratio LK / LG 0,0 0,6 0,6 0,6 0,6 angle α - 50° 50° 50° 50° Arrangement of recessed section and flat grooved section - Inside and outside Inside and outside Inside and outside Inside and outside S1 / S2 ratio 0,0 0,0 0,3 0,3 0,3 S2 / S ratio 0,0 0,0 0,0 0,0 0,006 S3 / S4 ratio 0,0 0,4 0,4 0,7 0,7 S4 / S ratio 0,0 0,0 0,0 0,0 0,006 ratio d11 / D - 0,4 0,4 0,4 0,4 ratio d12 / D - 0,4 0,4 0,4 0,4 Relationship of the misalignment- - 0,3 0,3 0,3 0,3 amount of the arrangement of recess sections Ratio of the misalignment amount of the arrangement of flat groove sections - 0,3 0,3 0,3 0,3 Presence / absence of the second recess section - Yes Yes Yes Yes Presence / absence of the third recess section and the flat groove section - Yes Yes Yes Yes Discharge rate (index) 100 103 106 106 106 Resistance to uneven wear (index) 100 102 104 106 106 [Table 1-II] Example 5 (State of the Art) Example 6 (State of the Art) Example 7 (State of the Art) Example 8 Example 9 Example 10 Presence / absence of the recess section Yes Yes Yes Yes Yes Yes Presence / absence of the flat groove section Yes Yes Yes Yes Yes Yes change in altitude Ongoing Ongoing Ongoing Ongoing Ongoing Ongoing recess section DK / DB ratio 0,5 0,8 0,6 0,6 0,6 0,6 DG / DK relationship 0,4 0,4 0,4 0,1 0,02 0,18 ratio LK / LG 0,6 0,6 0,6 0,6 0,6 0,6 angle α 50° 50° 50° 50° 50° 50° Arrangement of recessed section and flat grooved section Inside and outside Inside and outside Inside and outside Inside and outside Inside and outside Inside and outside S1 / S2 ratio 0,3 0,3 0,3 0,3 0,3 0,3 S2 / S ratio 0,006 0,006 0,006 0,006 0,006 0,006 S3 / S4 ratio 0,7 0,7 0,7 0,7 0,7 0,7 S4 / S ratio 0,006 0,006 0,006 0,006 0,006 0,006 ratio d11 / D 0,4 0,4 0,4 0,4 0,4 0,4 ratio d12 / D 0,4 0,4 0,4 0,4 0,4 0,4 Ratio of the misalignment amount of the arrangement of recess sections 0,3 0,3 0,3 0,3 0,3 0,3 Ratio of the misalignment amount of the arrangement of flat groove sections 0,3 0,3 0,3 0,3 0,3 0,3 Presence / absence of the second recess section Yes Yes Yes Yes Yes Yes Presence / absence of the third recess section and the flat groove section Yes Yes Yes Yes Yes Yes Discharge rate (index) 108 108 108 108 109 109 Resistance to uneven wear (index) 106 106 109 112 114 114 [Table 2-I] Example 11 Example 12 Example 13 Example 14 Example 15 Presence / absence of the recess section Yes Yes Yes Yes Yes Presence / absence of the flat groove section Yes Yes Yes Yes Yes Height change of the recess section Ongoing Ongoing Ongoing Ongoing Ongoing DK / DB ratio 0,6 0,6 0,6 0,6 0,6 DG / DK relationship 0,2 0,1 0,1 0,1 0,1 ratio LK / LG 0,6 0,6 0,05 0,20 0,50 angle α 50° 50° 50° 50° 50° Arrangement of recessed section and flat grooved section Inside and outside Inside and outside Inside and outside Inside and outside Inside and outside S1 / S2 ratio 0,3 0,3 0,3 0,3 0,3 S2 / S ratio 0,006 0,006 0,006 0,006 0,006 S3 / S4 ratio 0,7 0,7 0,7 0,7 0,7 S4 / S ratio 0,006 0,006 0,006 0,006 0,006 ratio d11 / D 0,4 0,4 0,4 0,4 0,4 ratio d12 / D 0,4 0,4 0,4 0,4 0,4 Ratio of the misalignment amount of the arrangement of recess sections 0,3 0,3 0,3 0,3 0,3 Ratio of the misalignment amount of the order 0,3 0,3 0,3 0,3 0,3 flat groove sections Presence / absence of the second recess section Yes Yes Yes Yes Yes Presence / absence of the third recess section and the flat groove section Yes Yes Yes Yes Yes Discharge rate (index) 109 112 112 112 112 Resistance to uneven wear (index) 115 112 112 113 110 [Table 2-II] Example 16 Example 17 Example 18 Example 19 Example 20 Presence / absence of the recess section Yes Yes Yes Yes Yes Presence / absence of the flat groove section Yes Yes Yes Yes Yes Height change of the recess section Ongoing Ongoing Ongoing Ongoing Ongoing DK / DB ratio 0,6 0,6 0,6 0,6 0,6 DG / DK relationship 0,1 0,1 0,1 0,1 0,1 ratio LK / LG 0,1 0,1 0,1 0,1 0,1 angle α 50° 50° 50° 30° 40° Arrangement of recesses inside and inside and inside and inside and inside and cut and flat groove section Outside Outside Outside Outside Outside S1 / S2 ratio 0,3 0,3 0,3 0,3 0,3 S2 / S ratio 0,006 0,006 0,006 0,006 0,006 S3 / S4 ratio 0,7 0,7 0,7 0,7 0,7 S4 / S ratio 0,006 0,006 0,006 0,006 0,006 ratio d11 / D 0,4 0,4 0,4 0,4 0,4 ratio d12 / D 0,4 0,4 0,4 0,4 0,4 Ratio of the misalignment amount of the arrangement of recess sections 0,3 0,6 0,3 0,3 0,3 Ratio of the misalignment amount of the arrangement of flat groove sections 0,3 0,5 0,3 0,3 0,3 Presence / absence of the second recess section Yes Yes Yes Yes Yes Presence / absence of the third recess section and the flat groove section Yes Yes Yes Yes Yes Discharge rate (index) 112 115 115 115 115 Resistance to uneven wear (index) 113 113 116 118 118 [Table 3-I] Example 21 Example 22 Example 23 Example 24 Example 25 Presence / absence of the recess section Yes Yes Yes Yes Yes Presence / absence of the flat groove section Yes Yes Yes Yes Yes Height change of the recess section Ongoing Ongoing Ongoing Ongoing Ongoing DK / DB ratio 0,6 0,6 0,6 0,6 0,6 DG / DK relationship 0,1 0,1 0,1 0,1 0,1 ratio LK / LG 0,1 0,1 0,1 0,1 0,1 angle α 45° 35° 35° 35° 35° Arrangement of recessed section and flat grooved section Inside and outside Inside and outside Only outside Inside only Inside and outside S1 / S2 ratio 0,3 0,3 0,3 0,3 0,1 S2 / S ratio 0,006 0,010 0,010 0,010 0,010 S3 / S4 ratio 0,7 0,7 0,7 0,7 0,7 S4 / S ratio 0,006 0,010 0,010 0,010 0,010 ratio d11 / D 0,4 0,4 0,4 0,4 0,4 ratio d12 / D 0,4 0,4 0,4 0,4 0,4 Ratio of the misalignment amount of the arrangement of recess sections 0,3 0,3 0,3 0,3 0,3 Ratio of the misalignment amount of the arrangement of flat groove sections 0,3 0,3 0,3 0,3 0,3 Presence / absence of the second recess section Yes Yes Yes Yes Yes Presence / absence of the third recess section and the flat groove section Yes Yes Yes Yes Yes Discharge rate (index) 115 115 114 114 114 Resistance to uneven wear (index) 118 120 120 120 120 [Table 3-II] Example 26 Example 27 Example 28 Example 29 Example 30 Presence / absence of the recess section Yes Yes Yes Yes Yes Presence / absence of the flat groove section Yes Yes Yes Yes Yes Height change of the recess section Ongoing Ongoing Ongoing Ongoing Ongoing DK / DB ratio 0,6 0,6 0,6 0,6 0,6 DG / DK relationship 0,1 0,1 0,1 0,1 0,1 ratio LK / LG 0,1 0,1 0,1 0,1 0,1 angle α 35° 35° 35° 35° 35° Arrangement of recessed section and flat grooved section Inside and outside Inside and outside Inside and outside Inside and outside Inside and outside S1 / S2 ratio 0,5 0,15 0,3 0,3 0,3 S2 / S ratio 0,010 0,010 0,010 0,005 0,010 S3 / S4 ratio 0,7 0,7 0,7 0,7 0,5 S4 / S ratio 0,010 0,010 0,010 0,005 0,010 ratio d11 / D 0,4 0,4 0,4 0,4 0,4 ratio d12 / D 0,4 0,4 0,4 0,4 0,4 Ratio of the misalignment amount of the arrangement of recess sections 0,3 0,3 0,3 0,3 0,3 Ratio of the misalignment amount of the arrangement of flat groove sections 0,3 0,3 0,3 0,3 0,3 Presence / absence of the second recess section Yes Yes Yes Yes Yes Presence / absence of the third recess section and the flat groove section Yes Yes Yes Yes Yes Discharge rate (index) 116 116 116 115 116 Resistance to uneven wear (index) 118 119 120 120 120 [Table 4-I] Example 31 Example 32 Example 33 Example 34 Example 35 Presence / absence of the recess section Yes Yes Yes Yes Yes Presence / absence of the flat groove section Yes Yes Yes Yes Yes Height change of the recess section Ongoing Ongoing Ongoing Ongoing Ongoing DK / DB ratio 0,6 0,6 0,6 0,6 0,6 DG / DK relationship 0,1 0,1 0,1 0,1 0,1 ratio LK / LG 0,1 0,1 0,1 0,1 0,1 angle α 35° 35° 35° 35° 35° Arrangement of recessed section and flat grooved section Inside and outside Inside and outside Inside and outside Inside and outside Inside and outside S1 / S2 ratio 0,3 0,3 0,3 0,3 0,3 S2 / S ratio 0,010 0,100 0,100 0,100 0,100 S3 / S4 ratio 0,9 0,7 0,7 0,7 0,7 S4 / S ratio 0,010 0,100 0,100 0,100 0,100 ratio d11 / D 0,4 0,4 0,1 0,2 0,3 ratio d12 / D 0,4 0,4 0,1 0,3 0,4 Ratio of the misalignment amount of the arrangement of recess sections 0,3 0,3 0,3 0,3 0,3 Ratio of the misalignment amount of the arrangement of flat groove sections 0,3 0,3 0,3 0,3 0,3 Presence / absence of the second recess section Yes Yes Yes Yes Yes Presence / absence of the third recess section and the flat groove section Yes Yes Yes Yes Yes Discharge rate (index) 116 116 116 116 116 Resistance to uneven wear (index) 118 121 122 123 122 [Table 4-II] Example 36 Example 37 Example 38 Example 39 Example 40 Presence / absence of the recess section Yes Yes Yes Yes Yes Presence / absence of the flat groove section Yes Yes Yes Yes Yes Height change of the recess section Ongoing Ongoing Ongoing Ongoing Ongoing DK / DB ratio 0,6 0,6 0,6 0,6 0,6 DG / DK relationship 0,1 0,1 0,1 0,1 0,1 ratio LK / LG 0,1 0,1 0,1 0,1 0,1 angle α 35° 35° 35° 35° 35° Arrangement of recessed section and flat grooved section Inside and outside Inside and outside Inside and outside Inside and outside Inside and outside S1 / S2 ratio 0,3 0,3 0,3 0,3 0,3 S2 / S ratio 0,100 0,100 0,100 0,100 0,100 S3 / S4 ratio 0,7 0,7 0,7 0,7 0,7 S4 / S ratio 0,100 0,100 0,100 0,100 0,100 ratio d11 / D 0,2 0,2 0,2 0,2 0,2 ratio d12 / D 0,3 0,3 0,3 0,3 0,3 Ratio of the misalignment amount of the arrangement of 0,1 0,5 0,3 0,3 0,3 recess sections Ratio of the misalignment amount of the arrangement of flat groove sections 0,1 0,5 0,3 0,3 0,3 Presence / absence of the second recess section Yes Yes No Yes Yes Presence / absence of the third recess section and the flat groove section Yes Yes Yes No Yes Discharge rate (index) 116 116 116 114 118 Resistance to uneven wear (index) 123 123 125 123 125 List of reference symbols 1 pneumatic tire 2. Tread section 3 Shoulder section 4 Side wall section 5 bead section 6 Carcass layer 7th belt layer 20C, 20S bridge section 21 Tread surface 22A, 22B Main circumferential groove 23G Flat groove section 23Gi Inner flat groove section 23Go Outer flat groove section 23K recess section 23Ki Inner recess section 23K Outer recess section 24 stud groove 25 Recess section 51 bead core 52 Bead fillers 71 belts 220 tread contact surface 221 Grooved floor section 222 Step section BK Block CL tire equator line

Claims

Pneumatic tire (1) comprising: two main circumferential grooves (22A, 22B) extending in the circumferential direction of the tire and arranged side by side in the width direction of the tire; and a first rib section (20C) defined by the two main circumferential grooves (22A, 22B), wherein the two main circumferential grooves (22A, 22B) comprise an inner main circumferential groove (22A) closest to an equatorial plane of the tire, and an outer main circumferential groove (22B) provided on an outer side in the tire width direction with respect to the inner main circumferential groove (22A), wherein the first rib section (20C) comprises a recess section (23Ki, 23Ko) extending in the tire width direction and connected to the main circumferential groove (22A, 22B), and a shallow groove section (23Gi, 23Go) connected to the recess section (23Ki, 23Ko) and terminating blindly in the first rib section (20C), and wherein a height of the recess section (23Ki,23Ko) to the associated main circumferential groove (22A, 22B) decreases continuously, wherein a ratio of a depth (DG) of the flat groove section (23Gi, 23Go) to a depth (DK) of the associated recess section (23Ki, 23Ko) is greater than 0 and equal to or less than 0.

2. Pneumatic tire (1) according to claim 1, wherein the height of the recess section (23Ki, 23Ko) decreases continuously from a height corresponding to a tire wear of 5% to a height corresponding to a tire wear of 70%. Pneumatic tire (1) according to claim 1 or 2, wherein the ratio of a depth (DK) of the recess section (23Ki, 23Ko) to a groove depth (DB) of the associated main circumferential groove (22A, 22B) is 0.50 or more and 0.80 or less. Pneumatic tire (1) according to one of claims 1 to 3, wherein a ratio of a length (LK) in the tire width direction of a flat section of a bottom section of the recess section (23Ki, 23Ko) to a length (LG) in the tire width direction of the flat groove section (23Gi, 23Go) is greater than 0 and equal to or less than 0.

5. Pneumatic tire (1) according to one of claims 1 to 4, wherein an angle of the recess section (23Ki, 23Ko) with respect to a normal of a tread contact surface (220) is greater than 0° and equal to or less than 45°. Pneumatic tire (1) according to any one of claims 1 to 5, wherein the recess section (23Ki, 23Ko) comprises an inner recess section (23Ki) extending in the tire width direction and connected to the inner main circumferential groove (22A), and an outer recess section (23Ko) extending in the tire width direction and connected to the outer main circumferential groove (22B), and the flat groove section (23Gi, 23Go) comprises an inner flat groove section (23Gi) connected to the inner recess section (23Ki) and terminating blindly in the first rib section (20C), and an outer flat groove section (23Go) connected to the outer recess section (23Ko) and terminating blindly in the first rib section (20C). Pneumatic tire (1) according to claim 6, wherein in the outer recess section (23Ko) and the outer flat groove section (23Go) connected to the outer recess section (23Ko) the ratio S1 / S2 of a projection area (S1) of the outer flat groove section (23Go) to a projection area (S2) of the outer recess section (23Ko) is 0.1 ≤ S1 / S2 ≤ 0.

5. Pneumatic tire (1) according to claim 7, further comprising: a plurality of lateral direction grooves (24) extending in the tire width direction between the inner main circumferential groove (22A) and the outer main circumferential groove (22B); and a block (BK) defined by the inner main circumferential groove (22A), the outer main circumferential groove (22B) and the plurality of lateral direction grooves (24), wherein the ratio S2 / S of the projection area S2 of the outer recess section (23Ko) to a ground contact area S of the block (BK) is 0 < S2 / S ≤ 0.

1. Pneumatic tire (1) according to claim 6, wherein in the inner recess section (23Ki) and the inner flat groove section (23Gi) connected to the inner recess section (23Ki) the ratio S3 / S4 of a projection area (S3) of the inner flat groove section (23Gi) to a projection area (S4) of the inner recess section (23Ki) is 0.5 ≤ S3 / S4 ≤ 0.

9. Pneumatic tire (1) according to claim 9, further comprising: a plurality of lateral direction grooves (24) extending in the tire width direction between the inner main circumferential groove (22A) and the outer main circumferential groove (22B); and a block (BK) defined by the inner main circumferential groove (22A), the outer main circumferential groove (22B) and the plurality of lateral direction grooves (24), wherein the ratio S4 / S of a projection area (S4) of the inner recess section (23Ki) to a ground contact area (S) of the block (BK) is 0 < S4 / S ≤ 0.

1. Pneumatic tire (1) according to any one of claims 6 to 10, wherein a ratio d11 / D of a distance (d11) in the tire width direction from an end section of the inner recess section (23Ki) near the inner main circumferential groove (22A) to a blind-ending end section of the inner flat groove section (23Gi) connected to the inner recess section (23Ki), to a distance (D) in the tire width direction between an end section of the inner recess section (23Ki) near the inner main circumferential groove (22A) and an end section of the outer recess section (23Ko) near the outer main circumferential groove is 0.1 or more and 0.3 or less, and a ratio d12 / D of a distance (d12) in the tire width direction from an end section of the outer recess section (23Ko) near the outer main circumferential groove (22B) to a blind-ending end section of the outer flat groove section (23Go) which is connected to the outer recess section (23Ko),where the distance (D) is 0.1 or more and 0.4 or less. Pneumatic tire (1) according to any one of claims 6 to 11, wherein a plurality of inner recess sections (23Ki) and a plurality of inner flat groove sections (23Gi) are arranged in the circumferential direction of the tire, a plurality of outer recess sections (23Ko) and a plurality of outer flat groove sections (23Go) are arranged in the circumferential direction of the tire, a ratio of a misalignment amount (PK) of an arrangement of the inner recess sections (23Ki) to a pitch distance length (PB1) of an arrangement of the outer recess sections (23Ko) is 0.1 or more and 0.5 or less, and a ratio of a misalignment amount (PG) of an arrangement of the inner flat groove sections (23Gi) to a pitch distance length (PB2) of an arrangement of the outer flat groove sections (23Go) is 0.1 or more and 0.5 or less. Pneumatic tire (1) according to any one of claims 6 to 12, further comprising: a second rib section (20-2) provided on the outer side in the tire width direction with respect to the outer main circumferential groove (22B); a second recess section (25) provided in the second rib section (20-2) and ending blindly in the second rib section (20-2); a third rib section (20-3) provided such that the inner main circumferential groove (22A) lies between them; a third recess section (23Ki) provided in the third rib section (20-3) extending in the tire width direction and connected to the inner main circumferential groove (22A); and a flat groove section (23Gi) connected to the third recess section (23Ki) and ending blindly in the third rib section (20-3).

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