pneumatic tires

Abstract

To provide a pneumatic tire that can improve snow-traction performance and reduce rolling resistance and can reduce air pumping sound.SOLUTION: A tire 1 as one example of embodiments includes a tread 10 having circumferential grooves and lug grooves 25 and 26 connected to the circumferential grooves and extending from a first side to a second side in a tire width direction. The tire 1 includes: two first raised parts 106 and 107 formed in groove bottoms at positions sandwiching ends at the circumferential groove sides of the lug grooves, in the circumferential grooves; second raised parts 103 formed in groove bottoms of portions at the circumferential groove side of the lug grooves; and third raised parts 108 formed in at least portions of groove bottoms of portions surrounded in three directions by the two first raised parts and the second raised parts, at an intersection part of extended portions of the lug grooves, of the circumferential grooves.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having a tread including circumferential grooves and lug grooves. [Background technology]

[0002] Conventionally, pneumatic tires having a tread including a plurality of circumferential grooves and a plurality of lug grooves connected to the circumferential grooves and extending in the tire width direction are known (see, for example, Patent Document 1). In addition, in the tire disclosed in Patent Document 1, in order to reduce rolling resistance while maintaining snow traction performance, raised portions are formed in the circumferential grooves except for the portions where they intersect with the extensions of the lug grooves, and in the lug grooves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6319385 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the tire disclosed in Patent Document 1, air tends to accumulate at the intersections of the circumferential grooves with the extensions of the lug grooves, which can easily cause air pumping noise due to the air accumulated at the intersections when a vehicle equipped with the tire is running.

[0005] An object of the present invention is to provide a pneumatic tire that can improve snow traction performance and reduce rolling resistance, as well as reduce air pumping noise. [Means for solving the problem]

[0006] The pneumatic tire of the present invention is a pneumatic tire having a tread including a circumferential groove and a lug groove connected to the circumferential groove and extending from a first side to a second side in the tire width direction, and includes two first raised portions formed on the groove bottom of the circumferential groove at positions sandwiching the circumferential groove side ends of the lug groove, a second raised portion formed on the groove bottom of the circumferential groove side portion of the lug groove, and a third raised portion formed on at least a part of the groove bottom of the circumferential groove at an intersection with the extension portion of the lug groove, in a portion surrounded on three sides by the two first raised portions and the second raised portion.

[0007] According to the above-described pneumatic tire, two first raised portions are formed at the groove bottom of the circumferential groove at positions sandwiching the circumferential groove-side ends of the lug grooves, and a second raised portion is formed at the groove bottom of the circumferential groove-side portion of the lug groove. This increases the rigidity of the land portion adjacent to the first raised portion of the circumferential groove and the land portion adjacent to the second raised portion of the lug groove. This reduces energy loss due to deformation of the land portion during vehicle travel, thereby reducing tire rolling resistance. Furthermore, the shear force acting on the packed snow in the groove when traveling on snowy roads increases the resistance between the tire and the road surface, improving snow traction performance. Furthermore, a third raised portion is formed at the groove bottom of the circumferential groove at the intersection with the lug groove extension, in a portion surrounded on three sides by the two first raised portions and the second raised portion. This reduces the amount of air trapped at the intersection, thereby reducing air pumping noise during travel. [Effects of the Invention]

[0008] The pneumatic tire according to the present invention can improve snow traction performance and reduce rolling resistance, while also reducing air pumping noise. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of a pneumatic tire as an example of an embodiment. [Figure 2]1 is a plan view of a pneumatic tire that is an example of an embodiment, showing a portion of a tread. [Figure 3] FIG. 2 is an enlarged plan view showing a part of the center region of the tread. [Figure 4] 4 is an enlarged perspective view of a recess in the oblique circumferential groove of FIG. 3. FIG. [Figure 5] 5 is an enlarged plan view showing the recess shown in FIG. 4. FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along the line A1-A1 in FIG. 5. [Figure 7A] FIG. 7 is a view corresponding to FIG. 6 and showing another example of a recess. [Figure 7B] FIG. 7 is a view corresponding to FIG. 6 and showing another example of a recess. [Figure 8] FIG. 5 is a view corresponding to FIG. 4 and showing another example of a recess. [Figure 9] FIG. 2 is an enlarged plan view showing a portion of a center region of a tread in an example embodiment. [Figure 10] 10 is an enlarged perspective view showing a connection portion between a first circumferential groove and a lug groove between center blocks, which is a first land portion, in FIG. 9. FIG. [Figure 11] FIG. 10 is an enlarged perspective view showing FIG. 9 cut along line BB. [Figure 12] 10 is an enlarged plan view of part C in FIG. 9. FIG. [Figure 13] FIG. 13 is a cross-sectional view taken along the line DD in FIG. 12. [Figure 14] FIG. 10 is an enlarged view of a cross section taken along the line EE in FIG. [Figure 15] 10 is an enlarged perspective view showing the example of the embodiment taken along line FF of FIG. 9. FIG. [Figure 16] 10 is an enlarged cross-sectional view showing a bridge corresponding to the second raised portion in part G of FIG. 9. FIG. [Figure 17] FIG. 16 is an enlarged cross-sectional view of line HH in FIG. [Figure 18] 10 is an enlarged cross-sectional view of a third raised portion of the third circumferential groove of FIG. 9. FIG. [Figure 19] 10 is a view corresponding to part I in FIG. 9, showing another example of the third raised portion. [Figure 20] 3 is an enlarged view of a part of a shoulder block that is a fifth land portion on the outer side in the vehicle width direction in FIG. 2. FIG. [Figure 21] FIG. 21 is an enlarged perspective view of an outer end portion in the tire width direction of the shoulder block of FIG. 20. [Figure 22] FIG. 21 is a perspective view showing the shoulder block of FIG. 20 cut along a plane including the ground contact end. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an example of an embodiment of a 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. Furthermore, the present invention includes selective combinations of the components of the multiple embodiments and modified examples described below.

[0011] In this specification, the terms wet road surface, snowy road surface, and dry road surface are used. A wet road surface refers to a road surface wet with rainwater or a road surface wet from melting snow and ice. A snowy road surface refers to a road surface covered with snow. A dry road surface refers to a dry road surface free of snow and ice. Hereinafter, for convenience of explanation, wet road surfaces and snowy road surfaces may be collectively referred to as "snow and ice road surfaces." Furthermore, although no particular reference will be made to driving performance on frozen road surfaces (ice performance) below, a pneumatic tire as an example of an embodiment has good ice performance in addition to good wet performance, snow performance, and dry performance.

[0012] FIG. 1 is a perspective view of a pneumatic tire 1 as an example of an embodiment. FIG. 2 is a plan view of the pneumatic tire 1, showing a portion of the tread. As shown in FIGS. 1 and 2, the pneumatic tire 1 has a tread 10, which is the portion that comes into contact with the road surface. Hereinafter, the "pneumatic tire 1" will be referred to as the "tire 1." The tread 10 has a tread pattern including a plurality of blocks, and is formed in an annular shape along the tire circumferential direction. The tire 1 does not limit the "main rotational direction," which is the rotational direction when a vehicle on which the tire 1 is mounted is traveling forward, but the following description will mainly focus on the case where the direction of arrow α in FIG. 1 is the main rotational direction.

[0013] In this specification, the terms "left and right" are used to describe the tire 1 and its components for convenience of explanation. The "right side" of the tire 1 means the right side when the tire 1 mounted on a vehicle is viewed from the front of the vehicle, and the "left side" means the left side when the tire 1 mounted on a vehicle is viewed from the front of the vehicle.

[0014] In the tire 1 of the embodiment, the mounting direction of the front and back of the tire 1 on the vehicle is specified. That is, the outer and inner sides of the tire 1 in the vehicle width direction are respectively specified. In FIG. 1, the tire 1 is mounted on the vehicle so that the right side is the outer side (OUT side) in the vehicle width direction and the left side is the inner side (IN side) in the vehicle width direction. When the tire 1 is used as the right wheel or the left wheel of the vehicle, the main rotation direction and left and right direction of the tire 1 can be reversed, and a common tire 1 can be used for both the left and right wheels.

[0015] The tread 10 has a plurality of circumferential grooves 20, 21, 22 and a plurality of lug grooves 25, 26 that extend while curving from a first side (left side) to a second side (right side) in the tire width direction. The tread 10 includes a plurality of blocks that are separated in the tire circumferential direction and in the tire width direction by being partitioned by the plurality of circumferential grooves 20, 21, 22 and the plurality of lug grooves 25, 26.

[0016] The blocks are island-shaped regions that protrude radially outward in the tire. As shown in Fig. 2, the tread 10 has a plurality of center blocks 50, a plurality of intermediate blocks 60, 70, and a plurality of shoulder blocks 80, 90, each of which will be described later. The tire equator CL, which will be described later, passes through the center block 50. The intermediate block 60 and the shoulder block 80 are disposed on the left side of the tread 10 in the width direction, and the intermediate block 70 and the shoulder block 90 are disposed on the right side of the tread 10 in the width direction.

[0017] The multiple circumferential grooves 20, 21, 22 include a first circumferential groove 20 formed near the center of the tread 10 in the width direction, and a second circumferential groove 21 and a third circumferential groove 22 provided on both the left and right sides of the first circumferential groove 20. Furthermore, multiple oblique circumferential grooves 31, which will be described later, are formed between the first circumferential groove 20 and the second circumferential groove 21 of the tread 10. The "tire width direction" and the "tread 10 width direction" are the same direction, and hereinafter, both terms will be used appropriately.

[0018] The first circumferential groove 20 and the second circumferential groove 21 are provided on either side of the tire widthwise center. The first circumferential groove 20 is provided closest to the tire widthwise center, i.e., the tire equator CL, among the multiple circumferential grooves 20, 21, and 22. The tire equator CL refers to a line extending in the tire circumferential direction that passes through the tire widthwise center.

[0019] Furthermore, the tread 10 is provided with a center region 40, which is a predetermined region in the tire width direction partitioned by the first circumferential groove 20 and the second circumferential groove 21. The center region 40 is divided into center blocks 50 and intermediate blocks 60, separated to the right and left, at each of a plurality of positions in the tire circumferential direction by a plurality of oblique circumferential grooves 31 (described later). The center blocks 50 are arranged adjacent to the first circumferential groove 20 on the center side in the tire width direction. The center blocks 50 correspond to a first land portion as a center land portion. A center block row 41 is formed by a plurality of center blocks 50 lined up in the tire circumferential direction.

[0020] The mediate blocks 60 correspond to second land portions. A plurality of mediate blocks 60 aligned in the tire circumferential direction form a mediate block row 44.

[0021] Furthermore, the tread 10 is formed with a shoulder block row 45 including a plurality of shoulder blocks 80 whose inner ends in the tire width direction are defined by the second circumferential groove 21. The tread 10 is also formed with an intermediate block row 46 including a plurality of intermediate blocks 70 defined by the first circumferential groove 20 and the third circumferential groove 22. The tread 10 is also formed with a shoulder block row 47 including a plurality of shoulder blocks 90 whose inner ends in the tire width direction are defined by the third circumferential groove 22. The shoulder blocks 80 correspond to the third land portion as a shoulder land portion. The intermediate blocks 70 correspond to the fourth land portion. The shoulder blocks 90 correspond to the fifth land portion as a shoulder land portion. The circumferential grooves 20, 21, 22 are aligned along the tire circumferential direction and have approximately the same width.

[0022] The lug grooves 25, 26 extend while curving from left to right in the tire width direction and are spaced apart from one another in the tire circumferential direction. In each of the block rows 41, 44-47, the lug grooves 25, 26 are inclined toward the same side with respect to the tire width direction between adjacent blocks in the tire circumferential direction. The lug grooves 25, 26 in the center block row 41 and the intermediate block row 44 are inclined more with respect to the tire width direction than the lug grooves 25, 26 in the other block rows 45-47. This facilitates improving snow traction performance in the lateral direction in the center of the tire width direction. The lug grooves 25, 26 are also shallower than the circumferential grooves 20-22.

[0023] Furthermore, the multiple lug grooves 25, 26 include multiple first lug grooves 25 and multiple second lug grooves 26 spaced apart in the tire circumferential direction. In the tread 10, one or more first lug grooves 25 and one or more second lug grooves 26 are alternately arranged in the tire circumferential direction. Hereinafter, a case will be described in which the first lug grooves 25 and the second lug grooves 26 are alternately arranged one by one in the tire circumferential direction in the tread 10. However, multiple first lug grooves 25 and multiple second lug grooves 26 may be alternately arranged one by one. The first lug grooves 25 are lug grooves that are crossed in the tire circumferential direction by intermediate portions of the oblique circumferential grooves 31 described below in the center region 40. On the other hand, the second lug grooves 26 are lug grooves that are connected by both ends of the oblique circumferential grooves 21. The widths of the lug grooves 25, 26 are basically approximately the same, but the ends of the lug grooves 25, 26 on the first circumferential groove 20 side in the intermediate block row 46 are narrower than other portions.

[0024] In this embodiment, blocks of the same type and assigned the same reference numerals are arranged in a line along the tire circumferential direction. The same number of blocks are arranged in a line along the tire circumferential direction, separated into multiple positions along the tire circumferential direction, along the lug grooves 25, 26 of the tread 10. That is, the tread 10 is formed with the same number of center blocks 50, intermediate blocks 60, 70, and shoulder blocks 80, 90.

[0025] The contact surface of each block is formed with a plurality of thin sipes extending substantially in the tire width direction or substantially in the tire circumferential direction. Each sipe is a thin groove narrower than the circumferential grooves 20-22 and the lug grooves 25, 26, and enhances the edge effect of catching snow and ice, achieving good braking / driving performance and handling stability on snowy and icy roads. A tire 1 having such a tread pattern is suitable, for example, for an all-season tire.

[0026] The tire 1 has sidewalls 12 formed in an annular shape along the tire circumferential direction, similar to the tread 10, on both sides of the tread 10 in the width direction.

[0027] Meanwhile, the shoulder blocks 80, 90 located at both widthwise ends of the tread 10 include a ground contact edge T (Figure 2), which is the outer edge of the ground contact patch in the tire width direction. The tire widthwise end of each shoulder block 80, 90 extends outward in the tire width direction from the ground contact edge T and gently curves radially inward in the tire so that the outer peripheral surface is convex outward. The portion of each shoulder block 80, 90 extending outward in the tire width direction from the ground contact edge T is called a buttress.

[0028] In this specification, the term "ground contact edge T" refers to both ends in the tire width direction of the part that comes into contact with a flat road surface when an unused tire 1 is mounted on a standard rim and inflated to the standard internal pressure, and a load of 70% of the standard load (maximum load capacity) at the standard internal pressure is applied.

[0029] Here, a "regular rim" is a rim specified by the tire standard, and is a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. "Regular internal pressure" is the "maximum air pressure" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "INFLATION PRESSURE" for ETRTO. "Regular load" is the "maximum load capacity" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "LOAD CAPACITY" for ETRTO.

[0030] A reinforcing structure (not shown) is provided on the inner circumferential side of the tire 1. The reinforcing structure includes a carcass, which is a rubber-coated cord layer, and a belt arranged between the tread pattern and the carcass. The carcass is composed of, for example, two carcass plies, and forms a tire framework that can withstand loads, impacts, air pressure, etc. The belt is a reinforcing band stretched in the circumferential direction of the tire, and tightens the carcass to increase the rigidity of the tread 10. An inner liner, which is a rubber layer that maintains air pressure, is attached to the inner circumferential surface of the carcass.

[0031] The tire 1 is also provided with beads 13 that are connected to the inner circumferential edges of the sidewalls 12, extend radially inward in the tire direction, and are curved so as to convexly form a curve toward the inside of the tire 1. The beads 13 are located on the inner side of the sidewalls 12 in the width direction of the tire 1 (on the tire equator CL side). The beads 13 are fixed to the rim of a wheel, and have a bead core and a bead filler provided inside.

[0032] Furthermore, in this embodiment, oblique circumferential grooves 31 are formed at a plurality of positions in the tire circumferential direction in the center region 40. These oblique circumferential grooves 31 improve the snow traction performance of the tire 1. The oblique circumferential grooves 31 will be described in detail later.

[0033] Furthermore, as shown in Figure 2, in the center block row 41, bridges 100, 101 are formed as raised portions in the lug grooves 25, 26 between the center blocks 50. These bridges 100, 101 improve the rigidity of the center blocks 50 that are adjacent in the tire circumferential direction. Raised portions 102, 103, 104, 105 are also provided in the lug grooves 25, 26 between the blocks of the intermediate block row 44, shoulder block row 45, intermediate block row 46, and shoulder block row 47. Each of the raised portions 102-105 improves the rigidity of the blocks that are adjacent in the tire circumferential direction.

[0034] Furthermore, a tapered surface is formed at each end of the bridge 100 formed in the second lug groove 26 between the center blocks 50, inclining downward toward the corresponding end. As will be described later, this increases the rigidity of the center block 50 and suppresses the deterioration of drainage performance in the center portion in the tire width direction while suppressing the influence of the tire rotation direction.

[0035] Furthermore, in the second circumferential groove 21, two raised portions 106, 107 serving as first raised portions are formed at the groove bottom at positions sandwiching the second circumferential groove 21-side ends of the lug grooves 25, 26 between the shoulder blocks 80 of the shoulder block row 45. Furthermore, in the second circumferential groove 21, at the intersection with the extended portions of the lug grooves 25, 26, a raised portion 108 serving as a third raised portion is formed at the groove bottom in a portion surrounded on three sides by the two raised portions 106, 107 and the raised portion 103 serving as the second raised portion. This improves snow traction performance and reduces rolling resistance, as will be described later, and reduces air pumping noise.

[0036] Furthermore, narrow grooves 109, 110 (described below) are formed inclined relative to the tire circumferential direction in the portion of the shoulder block 90 outward in the tire width direction from the ground contact edge T. This improves snow traction performance. Furthermore, the narrow grooves 109, 110 are connected to the sipes 81, 82 (lateral sipes) but are not connected to the lug grooves 25, 26, thereby improving drainage and increasing the rigidity of the shoulder block 90.

[0037] Next, the configurations of the oblique circumferential groove 31, the portion of the second lug groove 26 on the first circumferential groove 20 side and the first circumferential groove 20, the connection portion between the second and third circumferential grooves 21, 22 and the lug grooves 25, 26, and the narrow grooves 109, 110 of the shoulder block 90 will be described in detail. First, the oblique circumferential groove 31 will be described using Figs. 3 to 6.

[0038] Fig. 3 is an enlarged plan view showing a portion of the center region 40 of the tread 10. Fig. 4 is an enlarged perspective view of a recess 31a in the oblique circumferential groove 31 of Fig. 3. Fig. 5 is an enlarged plan view showing the recess 31a. Fig. 6 is a view showing a cross section taken along line A1-A1 in Fig. 5.

[0039] The oblique circumferential grooves 31 are provided at a plurality of positions in the tire circumferential direction in the center region 40. Each oblique circumferential groove 31 is a groove that crosses the first lug grooves 25 in the tire circumferential direction and is inclined with respect to the tire circumferential direction so that a first longitudinal end K1 is closer to the tire equator CL at the center in the tire width direction than a second longitudinal end K2. The oblique circumferential groove 31 crosses the first lug grooves 25 and connects two second lug grooves 26.

[0040] At the position where the first end K1 of the oblique circumferential groove 31 penetrates the second lug groove 26, a recess 31a is formed at the first end K1, which recesses into the wall surface 50a (FIG. 5) of the center block 50. The recess 31a extends along the second lug groove 26 and is recessed from the contact surface of the center block 50 and has a generally isosceles triangular shape when viewed from the outside in the tire radial direction, i.e., as shown in FIG. 5 in a plan view.

[0041] More specifically, the shape of the recess 31a in a plan view is an isosceles triangle having three vertices P1, P2, and P3, a first long side L1, a second long side L2, and a short side L3, and one corner corresponding to the vertex P1 is rounded. The lengths of the first long side L1 and the second long side L2 are approximately the same and are longer than the length of the short side L3. The first long side L1 is aligned along the longitudinal direction of the second lug groove 26. The vertex P1 of the isosceles triangle, which is the intersection of the second long side L2 and the short side L3, is recessed into the wall surface 50a. The vertex P is located farther from the tire equator CL at the center in the tire width direction than the vertex P2 of the isosceles triangle, which is the intersection of the first long side L1 and the second long side L2. The angle corresponding to the vertex P1 of the isosceles triangle is the intersection of the second long side L2 and the short side L3.

[0042] Furthermore, an inclined surface 31b is formed on the bottom surface of the recess 31a so as to approach the ground contact surface 50b of the center block 50 toward the inside of the center block 50. Specifically, as shown in FIG. 4, the left end of the lower edge DL of the bottom surface of the recess 31a adjacent to the second lug groove 26 is inclined slightly toward the ground contact surface toward the left end of the recess 31a. The left end of the recess 31a is slightly recessed toward the inside of the center block 50, forming the inclined surface 31b connecting the upper edge UL and the lower edge DL on the ground contact surface 50b. As a result, as shown in the cross-sectional view of FIG. 6, the cross section of the bottom surface of the recess 31a is linearly inclined toward the inside of the center block 50 where the recess 31a is formed (the left side of FIG. 6) so as to approach the ground contact surface 50b of the center block 50. Therefore, a relatively large space is formed inside the recess 31a that enters from the wall surface 50a of the center block 50, into which water can enter from the second lug grooves 26 and the oblique circumferential grooves 31. In this specification, when the terms "upper" and "lower" are used, the higher side in the direction of the protrusion of a raised part such as a block or protrusion will be referred to as "upper" and the lower side will be referred to as "lower."

[0043] Also, although not shown, in the A2-A2 line cross section and the A3-A3 line cross section of Figure 5, as in Figure 6, the cross section of the bottom surface of the recess 31a is a straight line that slopes linearly toward the inside of the center block 50 so as to approach the contact surface 50b of the center block 50.

[0044] 2, the plurality of oblique circumferential grooves 31 are connected around the entire circumference via parts of the second lug grooves 26 formed at multiple positions in the tire circumferential direction, thereby forming a zigzag shape. As shown in Fig. 4, the portion of each oblique circumferential groove 31 excluding the recessed portion 31a is deeper than the portions of each lug groove 25, 26 excluding the intersections with the oblique circumferential groove 31. The depth of the portion of the oblique circumferential groove 31 excluding the recessed portion 31a may be substantially the same as the depth of each lug groove 25, 26.

[0045] As a result, an oblique circumferential groove 31 inclined relative to the tire circumferential direction is formed across the first lug grooves 25 provided in the center region 40 of the tread 10. Furthermore, the recessed portion 31a provided at the first end K1 of the oblique circumferential groove 31 extends into the center block 50, and the first end K1 is closer to the tire equator CL at the tire widthwise center than the second end K2. This improves the vehicle's handling stability and cornering performance on snow. For example, the portions of the oblique circumferential groove 31 other than the recessed portion 31a are inclined relative to the tire circumferential direction, making it easier to catch and grip snow and ice in the circumferential and lateral directions of the tire. Furthermore, the recessed portion at the left end of the recessed portion 31a near the tire widthwise center of the oblique circumferential groove 31 makes it easier to catch and grip snow and ice in the lateral directions of the tire 1. This improves the snow traction performance of the tire 1 in the circumferential and lateral directions. Furthermore, since the first end K1 where the recess 31a of the oblique circumferential groove 31 is provided is closer to the center in the tire width direction than the second end K2, the handling stability and cornering performance on snow can be improved compared to when the recess is farther outward in the tire width direction.

[0046] Furthermore, the recesses 31a provided at the first ends K1 of the oblique circumferential grooves 31 extend along the second lug grooves 26. As a result, when the tire 1 rotates so that water flows from the second ends K2 to the first ends K1 of the oblique circumferential grooves 31 during vehicle travel on a wet road, the space between the recesses 31a and the road surface widens, preventing the wall or bottom of the recesses 31a from acting as a resistance to the water flow. Furthermore, the bottom of the recesses 31a is formed with an inclined surface 31b that approaches the contact surface 50b of the center blocks 50 toward the inside of the center blocks 50, preventing water from stagnating within the recesses 31a. Furthermore, unlike the case where the innermost portions of the recesses 31c are right-angled corners as shown by the two-dot chain line in FIG. 6 , reducing the rigidity of the center blocks 50 is reduced. This allows for excellent drainage of water from within the tire 1 grooves, thereby achieving a tire 1 that effectively prevents hydroplaning and further reduces a reduction in the rigidity of the center blocks 50.

[0047] For example, when the tire 1 rotates in the direction of arrow α in Fig. 3 during vehicle travel, it is conceivable that a water flow heading from the tire width direction center to the outside in the tire width direction along the second lug grooves 26 as indicated by arrow β in Fig. 3 and a water flow heading toward the rear in the rotation direction of the tire 1 along the oblique circumferential grooves 31 as indicated by arrow γ in Fig. 3 will merge. In this case, the recess 31a can increase the volume of the space at the merged portion, thereby suppressing water flow resistance and improving drainage.

[0048] Furthermore, in the tire 1, the shape of the recessed portion 31a in a plan view is an isosceles triangle with one corner rounded, which corresponds to the vertex P1, and therefore the generation of turbulence in the water flow at the back of the recessed portion 31a can be suppressed, making the water flow smoother in the grooves leading to the recessed portion 31a and improving drainage. Also, unlike when the shape of the recessed portion 31a in a plan view is rectangular, the recessed portion 31a can be prevented from becoming excessively large while suppressing resistance to the water flow at the water flow confluence point, thereby suppressing a decrease in the rigidity of the center block 50.

[0049] Fig. 7A shows a first example of another recess. In the configuration shown in Fig. 7A, the upper end of the inclined surface 31e formed on the bottom surface of the recess 31d is located radially inward of the tire contact patch 50b (toward the bottom in Fig. 7A). This configuration may slightly reduce the rigidity of the center block 50 compared to the configurations shown in Figs. 3 to 6, but the increased space within the recess 31a can further enhance the hydroplaning suppression effect.

[0050] FIG. 7B shows a second example of a different recess. In the configuration shown in FIG. 7B, the bottom surface of recess 31f is formed with convex surface 31g, which has a curved cross section and is convex outward toward the center block 50's ground contact surface 50b. A concave surface 31h, which has a rounded corner and continues from the inner end of convex surface 31g, has an arc-shaped cross section. While this configuration may slightly reduce the rigidity of the center block 50 compared to the configurations shown in FIGS. 3 to 6, it can increase the space within recess 31a, thereby enhancing the effectiveness of suppressing hydroplaning. Furthermore, it can smooth the flow of water between recess 31a and the grooves, improving drainage.

[0051] Fig. 8 shows a third example of a different recess. Unlike the configurations shown in Figs. 3 to 6, the planar shape of recess 31i is an isosceles triangle with unrounded corners. The bottom surface of recess 31a has a second long side L2 connecting vertices P1 and P2 as the upper edge UL, and an inclined surface 31j is formed connecting the upper edge UL and a lower edge DL on the bottom side of the groove. This configuration allows the area of ​​wall surface 31k at the left end of recess 31i to be increased, further improving lateral snow traction.

[0052] Next, the configuration of the portion of the second lug groove 26 on the side of the first circumferential groove 20 and the first circumferential groove 20 will be described in detail with reference to Figs. 9 to 14. Fig. 9 is an enlarged plan view showing a part of the center region 40 of the tread 10. Fig. 10 is an enlarged perspective view showing a connection portion between the first circumferential groove 20 and the second lug groove 26 between the center block 50 in Fig. 9. Fig. 11 is an enlarged perspective view showing Fig. 9 cut along line BB. Fig. 12 is an enlarged plan view showing part C in Fig. 9. Fig. 13 is a view showing a cross section taken along line DD in Fig. 12. Fig. 14 is an enlarged cross section taken along line EE in Fig. 9.

[0053] As shown in Figures 9 to 14, a plurality of center blocks 50 are arranged adjacent to each other on the tire widthwise center side of the first circumferential groove 20 that is close to the tire widthwise center. The lug grooves 25, 26 between the center blocks 50 extend to the right in the tire width direction and open to the first circumferential groove 20 side. A bridge 100 with a raised bottom surface is formed in the portion of the second lug groove 26 between the center blocks 50 on the first circumferential groove 20 side. In Figure 12, the bridge 100 is represented by a sandy area.

[0054] The bridge 100 is provided to increase the rigidity of adjacent center blocks 50. As shown in FIGS. 12 and 13, the bridge 100 has a generally trapezoidal cross section. Specifically, the bridge 100 has an upper surface 100a that is generally flat along the tire circumferential direction, and the side surfaces of the longitudinal center end of the second lug groove 26 and the first circumferential groove 20 end have tapered surfaces 100b, 100c that are inclined so as to descend toward the corresponding longitudinal end of the bridge 100. In FIG. 12, arrows J1, J2 shown on both side surfaces of the bridge 100 indicate that the corresponding side surfaces are inclined in a direction descending from the upper surface toward the tip of the arrow.

[0055] The second lug grooves 26 have wide portions 111 formed at their ends on the first circumferential groove 20 side, which are spaces having a substantially triangular shape in plan view and whose tire circumferential width is larger on the first circumferential groove 20 side than on the lug groove central side within the tire circumferential range W in Fig. 12. The tapered surface 100c of the bridge 100 on the first circumferential groove 20 side is provided within this wide portion 111.

[0056] As shown in Fig. 10, the widthwise ends of the bridge 100 are connected to the wall surface of the center block 50 via rounded portions 123 having an arc-shaped cross section. Alternatively, the widthwise ends of the bridge 100 may be connected directly to the wall surface without the rounded portions. As shown in Fig. 13, the maximum height HB of the bridge 100 can be set to, for example, between 30% and 40% of the depth HL of the second lug grooves 26.

[0057] 9, a bridge 101 with a raised bottom surface is also formed in the middle of the first lug groove 25 between the center blocks 50, adjacent to the second lug groove 26. Similar to bridge 100, bridge 101 has a trapezoidal cross section with tapered sides at both ends that are lower toward the corresponding longitudinal ends of bridge 101.

[0058] 9 to 11 and 14, a tapered protrusion 112 is formed on the bottom surface of the first circumferential groove 20 adjacent to a first side in the tire circumferential direction of the wide portion 111 (the lower side in FIG. 9, the left side in FIG. 10). The tapered protrusion 112 has a generally triangular shape in a plan view and is formed to protrude outward in the tire radial direction. Also, as shown in FIGS. 11 and 14, a first inclined surface 113 is provided on the upper surface of the tapered protrusion 112 such that the left side, which is the side of the lug grooves 25, 26 between the center blocks 50, is higher than the right side, which is the side of the mediate block 70.

[0059] 9 and 10, a second inclined surface 114 is formed on the entire side surface of the tapered protrusion 112 on the second side in the tire circumferential direction (upper side in FIG. 9, right side in FIG. 10) of the tapered protrusion 112. The second inclined surface 114 is inclined toward the second side in the tire circumferential direction toward the wide portion 111 in the tire width direction. As shown in FIG. 9, the second inclined surface 114 is substantially along the wall surface 111a of the wide portion 111 on the tapered protrusion 112 side.

[0060] Furthermore, a third inclined surface 115 is formed on the side surface of the tapered protrusion 112 on a first side in the tire circumferential direction (the lower side in FIG. 9, the left side in FIG. 10) that is inclined generally toward the second side in the tire circumferential direction toward the center block 50 in the tire width direction. The third inclined surface 115 is disposed adjacent to the second side in the tire circumferential direction of the opening of the first lug groove 25 on the first circumferential groove 20 side. The third inclined surface 115 is inclined with respect to the tire circumferential direction so as to be approximately along the longitudinal direction of the first lug groove 25.

[0061] According to the above configuration, the bridges 100, 101 are provided in the lug grooves 25, 26 between the center blocks 50, thereby increasing the rigidity of the center blocks 50. Furthermore, even when the tire rotates in a direction that causes water to flow from the first circumferential groove 20 near the center in the tire width direction to the lug grooves 25, 26 between the center blocks 50 when the vehicle is traveling on a wet road surface, the tapered surfaces 100c of each bridge 100, 101 make it easier for water to flow from the first circumferential groove 20 to the lug grooves 25, 26.

[0062] Specifically, when the tire 1 rotates in the direction of arrow α in Fig. 9, the tapered surface 100c (Fig. 12) of the bridge 100 makes it easier for water to flow from the first circumferential groove 20 to the second lug groove 26 along the direction indicated by arrow M1 in Fig. 9. On the other hand, when the tire 1 rotates in the direction opposite to the direction of arrow α in Fig. 9, the tapered surface 100b (Fig. 12) of the bridge 100 makes it easier for water to flow from the second lug groove 26 to the first circumferential groove 20, i.e., in the direction indicated by arrow M2 in Fig. 9. This makes it possible to realize a tire 1 that can increase the rigidity of the center block 50 and suppress a decrease in drainage performance in the center portion in the tire width direction while suppressing the influence of the tire rotation direction.

[0063] Furthermore, tapered protrusions 112 having first inclined surfaces 113 on their upper surfaces that are higher on the lug grooves 25, 26 side between the center blocks 50 are formed on the bottom surface of the first circumferential grooves 20. This makes it easier for water to flow from the first circumferential grooves 20 to the second lug grooves 26 between the center blocks 50 along the first inclined surfaces 113 when the tire 1 rotates in the direction of arrow α in Fig. 9. This further reduces the deterioration of drainage performance in the center part in the tire width direction.

[0064] Furthermore, a wide portion 111 is formed at the end of the second lug groove 26 on the side of the first circumferential groove 20, the tapered protrusion 112 is disposed adjacent to the wide portion 111 on a first side in the tire circumferential direction, and a second inclined surface 114 is formed on a side surface of the tapered protrusion 112 on a second side in the tire circumferential direction. As a result, when the tire rotates in the direction opposite to the direction of arrow α in Fig. 9 , water that has flowed from the second lug groove 26 into the first circumferential groove 20 can be drained by passing through the right side of the first circumferential groove 20 in the tire width direction and into the first circumferential groove 20 due to the inclination of the first inclined surface 113 of the tapered protrusion 112 and the inclination of the second inclined surface 114, regardless of the presence of the tapered protrusion 112.

[0065] Furthermore, a third inclined surface 115 is formed on a side surface of the tapered protrusion 112 on the first side in the tire circumferential direction. The third inclined surface 115 is inclined with respect to the tire circumferential direction so as to follow the longitudinal direction of the first lug grooves 25. As a result, when the tire 1 rotates in the direction of arrow α in Fig. 9, the third inclined surface 115 of the tapered protrusion 112 makes it easier for water to flow from the first circumferential groove 20 to the first lug groove 25. This further reduces the deterioration of drainage performance in the center part in the tire width direction.

[0066] In this example, the bridges 101, each having a trapezoidal cross section, are provided in the middle of the first lug grooves 25 between the center blocks 50, thereby increasing the rigidity of the center blocks 50 on both sides in the tire circumferential direction. Furthermore, similar to the bridges 100, the drainage from the first circumferential grooves 20 to the first lug grooves 25 can be improved.

[0067] Next, the configuration of the connection portions between the second and third circumferential grooves 21, 22 and the lug grooves will be described in detail. Fig. 15 is an enlarged perspective view showing an example of an embodiment, cut along line F-F in Fig. 9. Fig. 16 is an enlarged cross-sectional view showing the raised portion 103 of the second raised portion at part G in Fig. 9. Fig. 17 is an enlarged cross-section taken along line HH in Fig. 15.

[0068] 9 and 15, in the second circumferential groove 21, two raised portions 106, 107 as first raised portions are formed in the groove bottoms of the lug grooves 25, 26 at positions sandwiching the second circumferential groove 21-side ends of the lug grooves 25, 26. Each raised portion 106, 107 is formed so as to protrude radially outward in the tire. As shown in Fig. 9, the shape of each raised portion 106, 107 in a plan view is a substantially triangular shape with its base connected to the wall surface of the shoulder block 80 and its apex connected to the wall surface on the intermediate block 60 side.

[0069] 15 and 16, the upper surface of each raised portion 106, 107 forms an inclined surface S that is inclined so as to rise radially outward in the tire direction toward the shoulder block 80. As a result, when the vehicle runs on a wet road surface and the tire 1 rotates in the direction of arrow α in FIG. 9 or in the direction opposite to the direction of arrow α, the inclined surface S of each raised portion 106, 107 makes it easier for water to flow from the second circumferential groove 21 to the lug grooves 25, 26 between the shoulder blocks 80. Therefore, even when raised portions 103 are provided in the lug grooves 25, 26 as second raised portions as described below, drainage performance can be improved.

[0070] Specifically, as shown in FIGS. 9 and 16 , a raised portion 103 that protrudes radially outward from the tire is provided at the groove bottom of each lug groove 25, 26 between the shoulder blocks 80, on the second circumferential groove 21 side. Similar to the bridges 100, 101 provided in the lug grooves 25, 26 between the center blocks 50, the raised portion 103 has a generally trapezoidal cross section. Specifically, the raised portion 103 has a generally flat upper surface along the tire circumferential direction, and two tapered surfaces 103 a, 103 b on both longitudinal sides of the lug grooves 25, 26 that slope downward toward the corresponding end of the raised portion 103. The raised portion 103 is provided to increase the rigidity of the shoulder block 80, and both widthwise ends are connected to the wall surfaces of the shoulder blocks 80 adjacent in the tire circumferential direction.

[0071] As described above, an inclined surface S is formed on the upper surface of each raised portion 106, 107 in the second circumferential groove 21. This makes it easier for water to flow from the second circumferential groove 21 to the lug grooves 25, 26 when the vehicle is traveling on a wet road surface, regardless of the presence of the bridge 100, thereby improving drainage performance.

[0072] On the other hand, when the two raised portions 106, 107 are formed in the second circumferential groove 21 and the raised portions 103 are provided in the lug grooves 25, 26, if the space at the intersection of the second circumferential groove 21 with the extensions of the lug grooves 25, 26 is relatively wide, air tends to accumulate in this space. As a result, when a vehicle equipped with the tire 1 runs on a dry road surface, air accumulated in the space at the intersection tends to generate air pumping noise.

[0073] In this example, to solve this problem, as shown in Figures 9, 15, and 17, a raised portion 108 serving as a third raised portion is formed at the groove bottom of a portion surrounded on three sides by the two raised portions 106, 107 and the raised portion 103 at the intersection of the second circumferential groove 21 with the extended portions of the lug grooves 25, 26. The raised portion 108 protrudes radially outward so as to be higher than the reference surface 21a (Figures 15 and 17), which is the lowest portion of the second circumferential groove 21.

[0074] 9, the raised portion 108 is shown by a sandy portion in the second circumferential groove 21. As shown in Fig. 9, the raised portion 108 has a substantially trapezoidal shape in a plan view, and both circumferential edge portions of the raised portion 108 are connected to the wall surfaces of the circumferential end portions of the two raised portions 106, 107 on both sides.

[0075] 17, the upper surface of the raised portion 108 is generally flat and has a constant vertical height from the reference plane 21a. Both end edges of the raised portion 108 in the tire width direction are connected to the wall surfaces of the second circumferential groove 21. As shown in FIG. 15, the upper surface of the raised portion 108 is lower than the upper surfaces of the raised portions 106 and 107. In this example, the height positions of the lowest ends of the inclined surfaces S of the raised portions 106 and 107 and the upper surface of the raised portion 108 are approximately the same.

[0076] Furthermore, as shown in Figure 9, the second circumferential groove 21 side end of the lug grooves 25, 26 between the shoulder blocks 80 faces the wall surface of the tire width direction end of the intermediate block 60 on the extension line of the lug grooves 25, 26, via the portion of the second circumferential groove 21 where the raised portion 108 is provided at the groove bottom.

[0077] According to the above configuration, two raised portions 106, 107 are formed in the groove bottom of the second circumferential groove 21 at positions sandwiching the second circumferential groove 21-side ends of the lug grooves 25, 26. Furthermore, a raised portion 103 is formed in the groove bottom of the lug grooves 25, 26 on the second circumferential groove 21 side. This increases the rigidity of the shoulder block 80 adjacent to the raised portions 106, 107 of the second circumferential groove 21 and the shoulder block 80 adjacent to the raised portions 103 of the lug grooves 25, 26. Therefore, the rigidity of the shoulder block 80 is increased by one of the raised portions 106, 107 and the raised portion 103. This reduces energy loss due to block deformation during vehicle travel, thereby reducing the rolling resistance of the tire 1. Furthermore, when traveling on a snowy road, shear force acting on the snow packed in the grooves increases resistance between the tire 1 and the road surface, improving snow traction performance.

[0078] Furthermore, at the intersection of the second circumferential groove 21 with the extensions of the lug grooves 25, 26 between the shoulder blocks 80, a raised portion 108 is formed at the groove bottom in a portion surrounded on three sides by the two raised portions 106, 107 and the raised portion 103. This reduces the volume of the space at the intersection, thereby reducing the amount of air trapped therein. This reduces the air pumping noise during driving.

[0079] Furthermore, the ends of the lug grooves 25, 26 between the shoulder blocks 80 on the side of the second circumferential groove 21 face the wall surface of the mediate block 60 on the extension line of the lug grooves 25, 26, via the portion of the second circumferential groove 21 where the raised portions 108 are provided at the groove bottom. As a result, the above-mentioned intersection of the second circumferential groove 21 is surrounded on all sides by the three raised portions 106, 107, 108 and the wall surface of the mediate block 60. For this reason, air tends to be more difficult to discharge from the intersection when the vehicle is running, but the raised portions 108 can reduce the amount of air trapped, so the effect of providing the raised portions 108 becomes more pronounced.

[0080] 9 , in the third circumferential groove 22, two raised portions 116, 117 having a generally triangular shape in plan view are also formed on the groove bottom at positions sandwiching the third circumferential groove 22-side ends of the lug grooves 25, 26 between the shoulder blocks 90. Furthermore, a raised portion 105 is formed on the groove bottom on the third circumferential groove 22 side of the lug grooves 25, 26 between the shoulder blocks 90. The raised portion 105 has a tapered surface that becomes lower toward the end only on the side surface of the longitudinal center end of the lug grooves 25, 26, and the third circumferential groove 22-side end coincides with the wall surface of the third circumferential groove 22, so no tapered surface is formed.

[0081] Furthermore, at the intersection of the third circumferential groove 22 with the extensions of the lug grooves 25, 26 between the shoulder blocks 90, a raised portion 118 is formed at the groove bottom in a portion surrounded on three sides by the three raised portions 116, 117, 105. In Figure 9, the raised portion 118 is shown by a sanded portion in the third circumferential groove 22.

[0082] 18 is an enlarged cross-sectional view of the raised portion 118 in the third circumferential groove 22. As shown in Fig. 18, the upper surface of the raised portion 118 is also substantially flat and has a constant height in the up-down direction from the reference plane 22a of the third circumferential groove 22, similar to the raised portion 108 in the second circumferential groove 21. Both end edges of the raised portion 118 in the tire width direction are connected to the wall surfaces of the second circumferential groove 21.

[0083] This also reduces the amount of air trapped at the intersection of the third circumferential grooves 22 with the extensions of the lug grooves between the shoulder blocks 90. This reduces air pumping noise during running. As shown in FIG. 9 , at this intersection, unlike the intersection of the second circumferential grooves 21, the second circumferential groove 21-side end of the lug groove between the shoulder blocks 90 and the second circumferential groove 21-side end of the lug groove between the intermediate blocks 70 face each other on the extension lines of the respective lug grooves. This makes it easier for air to be discharged at the intersection of the third circumferential grooves 22 than at the intersection of the second circumferential grooves 21. The effect of providing the raised portion 108 is greater at the intersection of the second circumferential grooves 21.

[0084] FIG. 19 is a diagram corresponding to part I in FIG. 9 and shows another example of the third raised portion. The raised portion 119 serving as the third raised portion shown in FIG. 19 has a thin linear shape extending in the tire width direction in a plan view, and both ends in the tire circumferential direction are not connected to the wall surfaces of the two raised portions 106, 107. Therefore, although the effect is inferior to that of the raised portion 108 shown in FIG. 9 , the effect of reducing the volume of the space at the intersection of the second circumferential groove 21 with the extensions of the lug grooves 25, 26 between the shoulder blocks 80 can be obtained, thereby reducing air pumping noise during running. In this way, the third raised portion may be configured to be formed only in a portion of the groove bottom of the circumferential groove surrounded on three sides by the two first raised portions and the second raised portion at the intersection with the extensions of the lug grooves.

[0085] Next, the narrow grooves 109, 110 of the shoulder block 90 will be described with reference to Figures 20 to 22. Figure 20 is an enlarged view of a portion of the shoulder block 90 in Figure 2. Figure 21 is an enlarged perspective view of the outer end of the shoulder block 90 in the tire width direction. Figure 22 is a perspective view of the shoulder block 90 cut along a plane including the ground contact edge T.

[0086] A plurality of lug grooves 25, 26 are formed between the plurality of shoulder blocks 90 of the shoulder block row 47, extending from the left side to the right side in the tire width direction while being separated in the tire circumferential direction. The plurality of shoulder blocks 90 are separated in the tire circumferential direction by the lug grooves 25, 26. When the tire 1 is mounted on a vehicle, the shoulder blocks 90 are provided at the end located on the outer side in the vehicle width direction.

[0087] Two lateral sipes, 81 and 82, extending from the left side to the right side in the tire width direction are provided on the contact surface of each shoulder block 90. ​​Therefore, each sipe 81 and 82 is provided between two lug grooves 25 and 26 that are adjacent in the tire circumferential direction. In the shoulder block 90, each sipe 81 and 82 has the same width over its entire length in the longitudinal direction, and is narrower than the maximum width of the two lug grooves 25 and 26 that are provided between the sipes 81 and 82.

[0088] Ends 81a, 82a, which are the inner ends in the tire width direction of each sipe 81, 82, open into the wall surface at the inner end in the tire width direction of the shoulder block 90. ​​Ends 81b, 82b, which are the outer ends in the tire width direction of each sipe 81, 82, terminate inside the shoulder block 90 and do not open into the wall surface of the shoulder block 90. ​​A serpentine portion is provided in part of the sipes 81, 82, but the serpentine portion may be omitted.

[0089] Furthermore, two narrow grooves 109, 110 are formed in the shoulder block row 47 between the two lug grooves 25, 26 that sandwich the sipes 81, 82, i.e., on the outer side in the tire width direction of the ground contact edge T of the upper surface of the shoulder block 90, inclined to the same side in the tire circumferential direction over their entire length. The narrow groove 109 is longer than the narrow groove 110, and the inner end of the narrow groove 109 in the tire width direction is connected to the end 81b of the sipe 81.

[0090] The narrow groove 110 is inclined toward the outer side in the tire width direction on the same side in the tire circumferential direction as the narrow groove 109. The narrow groove 110 has an inner end in the tire width direction connected to the sipe 82 so as to branch off from the vicinity of the outer end of the sipe 82 in the tire width direction.

[0091] Each of the narrow grooves 109, 110 is shallower than each of the sipes 81, 82 and has, for example, an arc-shaped cross section that widens toward the open end. The shape of the narrow groove is not limited to this, and it may have a generally rectangular cross section with an open upper end, or a generally flat bottom surface with wall surfaces on both sides in the width direction inclined with respect to the bottom surface so that the width widens toward the open end.

[0092] Furthermore, each narrow groove 109, 110 is separated over its entire length within the shoulder block 90 from the two lug grooves 25, 26 that define both ends of the shoulder block 90 in the tire circumferential direction. As a result, each narrow groove 109, 110 is not connected to the lug grooves 25, 26 between the shoulder blocks 90.

[0093] Furthermore, the outer ends of each narrow groove 109, 110 in the tire width direction do not open onto the wall surface of the shoulder block 90 but terminate within the shoulder block 90. ​​Therefore, each narrow groove 109, 110 does not open onto the wall surface of the shoulder block 90.

[0094] Furthermore, shallow grooves 120 that are J-shaped in plan view are formed in a portion of the upper surface of each shoulder block 90 that is located outward in the tire width direction from the ground contact edge T and further outward in the tire width direction from the narrow grooves 109, 110. The shallow groove 120 has a straight portion 121 that is located outward in the tire width direction from the curved portion 122 and extends along the tire circumferential direction. The shallow groove 120 has approximately the same depth as the narrow grooves 109, 110. The width of the shallow groove 120 increases from the end on the curved portion 122 side toward the end on the straight portion 121 side at both ends in the longitudinal direction.

[0095] According to the above configuration, narrow grooves 109, 110 inclined relative to the tire circumferential direction are formed in an area called a buttress that is located on the outer side in the tire width direction of the ground-contact edge T of the shoulder block 90. ​​Furthermore, the narrow grooves 109, 110 are not connected to the sipes 81, 82 or the two lug grooves 25, 26 that sandwich the narrow grooves 109, 110. This increases the rigidity of the buttress, thereby improving snow traction performance.

[0096] Furthermore, because the narrow grooves 109, 110 are connected to the sipes 81, 82, drainage is improved. Furthermore, because the narrow grooves 109, 110 are inclined to the same side relative to the tire circumferential direction along their entire length, the sipes 81, 82, which can be made deeper, can be made longer while improving drainage in the narrow grooves 109, 110. This improves drainage in the shoulder blocks 90.

[0097] Furthermore, because the narrow grooves 109, 110 are shallower than the sipes 81, 82, even though the thickness of the rubber portion of the tire is reduced at the buttresses at the outer ends in the tire width direction, making the narrow grooves 109, 110 shallower prevents the thickness of the bottoms of the narrow grooves 109, 110 from becoming excessively thin. This makes it possible to suppress the occurrence of cracks at the groove bottoms of the narrow grooves 109, 110. In particular, the buttresses are exposed to sunlight and the rubber tends to harden, but even in this case, the occurrence of cracks is easily suppressed. This makes the effects of making the narrow grooves 109, 110 shallower remarkable.

[0098] In the above embodiment, two narrow grooves are formed in each shoulder block 90, but only one narrow groove or three or more narrow grooves may be formed in each shoulder block.

[0099] In the above embodiment, the shoulder land portion is formed of a plurality of blocks divided in the tire circumferential direction by lug grooves. However, the shoulder land portion may not be divided into a plurality of blocks in the tire circumferential direction by forming lug grooves over the entire tire width direction. In this case, a narrow groove may be formed over the entire tire width direction outside the contact edge, inclined relative to the tire circumferential direction, connected to the lateral sipes but not connected to the lug grooves. [Explanation of symbols]

[0100] 1 tire, 10 tread, 12 sidewall, 13 bead, 20 first circumferential groove, 21 second circumferential groove, 21a reference surface, 22 third circumferential groove, 22a reference surface, 25 first lug groove, 26 second lug groove, 31 oblique circumferential groove, 31a recess, 31b inclined surface, 31c, 31d recess, 31e inclined surface, 31f recess, 31g convex surface, 31h concave surface, 31i recess, 31j inclined surface, 31k wall surface, 40 center region, 41 center block row, 44 mediate block row, 45 shoulder block row, 46 mediate block row, 47 shoulder block row, 50 center block, 50a wall surface, 50b contact surface, 60 mediate block, 70 mediate block, 80 shoulder block, 81, 82 Sipes, 81a, 81b, 82a, 82b ends, 90 shoulder blocks, 100, 101 bridges, 100a upper surfaces, 100b, 100c tapered surfaces, 102-108 raised portions, 109, 110 narrow grooves, 111 wide portions, 112 tapered protrusions, 113 first inclined surfaces, 114 second inclined surfaces, 115 third inclined surfaces, 116-118 raised portions, 120 shallow grooves, 121 straight portions, 122 curved portions, 123 R portions, CL tire equator, T ground contact edge.

Claims

1. A pneumatic tire having a tread including a circumferential groove and a lug groove connected to the circumferential groove and extending from a first side to a second side in a tire width direction, In the circumferential groove, two first raised portions are formed on the groove bottom at positions sandwiching the circumferential groove side ends of the lug grooves; a second raised portion formed on a groove bottom of the circumferential groove side portion of the lug groove; The circumferential groove includes a third raised portion formed on at least a part of a groove bottom of a portion surrounded on three sides by the two first raised portions and the second raised portion at an intersection with an extension portion of the lug groove, The shape of each of the two first raised portions in a plan view on the tire radially outer surface is such that both ends in the tire width direction are connected to wall surfaces of two land portions that face each other across the circumferential groove, and each of the two first raised portions has a radially outer surface that is inclined so as to be higher radially outward in the tire toward the land portion on the second raised portion side of the two land portions. Pneumatic tires.

2. The tire radial outer surfaces of the two first raised portions are connected to the lower end of the wall surface of the land portion opposite the second raised portion of the two land portions, The pneumatic tire according to claim 1 .

3. Both tire width direction edge portions of the third raised portion are connected to the wall surfaces of the circumferential groove, and both tire circumferential direction edge portions of the third raised portion are connected to the wall surfaces of the tire circumferential ends of the two first raised portions. The pneumatic tire according to claim 1 or 2.

4. The longitudinal end of the second raised portion on the circumferential groove side does not reach the circumferential groove, The pneumatic tire according to any one of claims 1 to 3.

5. the tread includes a plurality of land portions separated by the circumferential grooves, The circumferential groove side end of the lug groove faces a wall surface at an end in the tire width direction of the land portion, via a portion in the circumferential groove where the third raised portion is provided at the groove bottom, on an extension line of the lug groove. The pneumatic tire according to any one of claims 1 to 4.

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