Pneumatic tires

Abstract

A tire (1) as an example of an embodiment of the present invention includes a tread portion (10), the tread portion (10) having: a circumferential groove; and lug grooves (25, 26) connected to the circumferential groove and extending from a first side to a second side in the tire width direction. The tire (1) includes: two first protrusions (106, 107) formed at the groove bottom of the circumferential groove at both sides of the circumferential groove side end of the lug groove; a second protrusion (103) formed at the groove bottom of the circumferential groove side portion of the lug groove; and a third protrusion (108) formed at least a portion of the groove bottom of a portion surrounded in three directions by the two first protrusions and the second protrusion at an intersection with an extension of the lug groove in the circumferential groove.

Description

[0001] The contents of Japanese Tokugan Application No. 2021-177088 filed on October 29, 2021 are incorporated into this specification. Technical Field

[0002] The present disclosure relates to a pneumatic tire, and more particularly, to a pneumatic tire including a tread portion having a circumferential groove and a lug groove. Background Art

[0003] Conventionally, a pneumatic tire is known that includes a tread portion having a plurality of circumferential grooves and a plurality of transverse grooves extending in the tire width direction and connected to the circumferential grooves (for example, see Japanese Patent No. 6319385). In addition, in the tire disclosed in Japanese Patent No. 6319385, in order to maintain snow traction performance and reduce rolling resistance, protrusions are formed on the circumferential grooves except for the intersection with the extended portion of the transverse grooves and on the transverse grooves.

[0004] However, in the tire disclosed in Japanese Patent No. 6319385, air tends to be retained at the intersection of the circumferential groove and the extension of the lug groove, so that when a vehicle equipped with the tire is running, tire noise, i.e., air pumping sound caused by air retained at the intersection, tends to be generated. Summary of the invention

[0005] An object of the present disclosure is to provide a pneumatic tire that can achieve improved snow traction performance and reduced rolling resistance, and can reduce air pumping noise.

[0006] The pneumatic tire involved in the present disclosure has a tread portion, which has: a circumferential groove; and a lug groove, which is connected to the circumferential groove and extends from a first side to a second side in the tire width direction, and the pneumatic tire includes: two first protrusions, which are formed in the circumferential groove at the groove bottom on both sides of the circumferential groove side end of the lug groove; a second protrusion, which is formed at the groove bottom of the circumferential groove side portion of the lug groove; and a third protrusion, which is formed in the intersection of the circumferential groove and the extension of the lug groove, and is formed in at least a part of the groove bottom of the portion surrounded in three directions by the two first protrusions and the second protrusion.

[0007] According to the above-mentioned pneumatic tire, in the circumferential groove, two first protrusions are formed at the groove bottom at both sides of the circumferential groove side end of the lug groove, and a second protrusion is formed at the groove bottom of the circumferential groove side portion of the lug groove. As a result, the rigidity of the land portion adjacent to the first protrusion of the circumferential groove and the land portion adjacent to the second protrusion of the lug groove can be improved. Therefore, the energy loss caused by the deformation of the land portion during vehicle driving can be reduced, and thus the rolling resistance of the tire can be reduced. In addition, the shear force acting on the snow compacted in the groove when driving on a snowy road surface can be used to increase the resistance between the tire and the road surface, thereby improving the snow traction performance. In addition, a third protrusion is formed at the intersection of the circumferential groove and the extension of the lug groove, and at the groove bottom of the portion surrounded by the two first protrusions and the second protrusion in three directions. As a result, the amount of trapped air in the intersection can be reduced, and thus the air pumping sound during driving can be reduced.

[0008] According to the pneumatic tire according to the present disclosure, it is possible to improve snow traction performance and reduce rolling resistance, and to reduce air pumping noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a perspective view of a pneumatic tire as an example of an embodiment.

[0010] Figure 2 It is a plan view of a pneumatic tire as an example of an embodiment, and is a view showing a part of a tread portion.

[0011] Figure 3 It is a plan view showing a part of the central area of ​​the tread portion in an enlarged manner.

[0012] Figure 4 yes Figure 3 An enlarged stereoscopic view of the concave portion of the inclined circumferential groove.

[0013] Figure 5 It is enlarged to show Figure 4 A top view of the recess is shown.

[0014] Figure 6 It is shown Figure 5 Figure 2 is a cross-section of the A1-A1 line in FIG.

[0015] Fig. 7A is a diagram showing another example of a concave portion. Figure 6 The corresponding figure.

[0016] Figure 7B is a diagram showing another example of a concave portion. Figure 6 The corresponding figure.

[0017] Figure 8 is a diagram showing another example of a concave portion. Figure 4The corresponding figure.

[0018] Fig. 9 This is a plan view showing an enlarged portion of a central region of a tread portion in one example of the embodiment.

[0019] Fig.10 It is enlarged to show Fig. 9 A perspective view of the connecting portion between the first circumferential groove and the lug groove between the central pattern block as the first land portion.

[0020] Fig.11 BB line pair Fig. 9 An enlarged perspective view showing a cutaway view.

[0021] Fig.12 It is enlarged to show Fig. 9 Top view of section C.

[0022] Fig.13 It is shown Fig.12 Figure 2. DD line cross section of FIG.

[0023] Fig.14 yes Fig. 9 Enlarged view of the EE line cross section.

[0024] Fig.15 In one example of implementation, FF line pairs are used. Fig. 9 An enlarged perspective view showing a cutaway view.

[0025] Fig.16 is equivalent to Fig. 9 An enlarged cross-sectional view of the bridging portion of the second protrusion of portion G.

[0026] Fig.17 yes Fig.15 Magnified view of the HH line cross section.

[0027] Fig.18 yes Fig. 9 An enlarged cross-sectional view of the third protrusion of the third circumferential groove.

[0028] Fig.19 is a diagram showing another example of the third protrusion. Fig. 9 The corresponding figure of part I.

[0029] Fig. 20 It is enlarged to show Figure 2 FIG. 1 is a diagram showing a portion of a shoulder block serving as a fifth land portion on the vehicle width direction outer side.

[0030] Fig.21 yes Fig. 20 An enlarged perspective view of the outer end of the shoulder pattern block in the tire width direction.

[0031] Fig. 22 The plane containing the ground terminal is Fig. 20 A three-dimensional view showing a shoulder pattern block cut away. DETAILED DESCRIPTION

[0032] Hereinafter, an example of an embodiment of the pneumatic tire involved in the present disclosure will be described in detail with reference to the accompanying drawings. The embodiment described below is an example after all, and the present disclosure is not limited to the following embodiment. In addition, the present disclosure includes a technical solution formed by selectively combining the various structural elements of the multiple embodiments and modified examples described below.

[0033] In addition, in this specification, the terms wet road surface, snowy road surface, and dry road surface are used. Wet road surface means a road surface wetted by rainwater and a road surface wetted by melted ice and snow. Snowy road surface means a road surface covered with snow. In addition, dry road surface means a dry road surface without ice or snow. In the following, for the sake of convenience, wet road surfaces and snowy road surfaces are sometimes collectively referred to as "ice and snow road surfaces." In addition, although the driving performance on frozen roads (ice performance) is not specifically described below, the pneumatic tire as an example of an embodiment has good ice performance in addition to good wet road performance, snow performance, and dry road performance.

[0034] Figure 1 It is a perspective view of a pneumatic tire 1 as an example of the embodiment. Figure 2 FIG. 1 is a top view of the pneumatic tire 1, showing a portion of the tread portion. Figure 1 , Figure 2 As shown in FIG. 1 , the pneumatic tire 1 includes a tread portion 10 as a portion that contacts the road surface. Hereinafter, the "pneumatic tire 1" will be referred to as "tire 1". The tread portion 10 has a tread pattern including a plurality of pattern blocks and is formed in a ring shape along the tire circumferential direction. The tire 1 does not limit the rotation direction of the vehicle equipped with the tire 1 when it is moving forward, i.e., the "main rotation direction". Figure 1 The case where the direction of arrow α is the main rotation direction is described below.

[0035] In this specification, the terms "left and right" are used for convenience of explanation with respect to the tire 1 and its structural elements. The "right side" of the tire 1 means the right side when the tire 1 is mounted on the vehicle as viewed from the front of the vehicle, and the "left side" means the left side when the tire 1 is mounted on the vehicle as viewed from the front of the vehicle.

[0036] Regarding the tire 1 of the embodiment, the mounting direction of the front and back surfaces of the tire 1 relative to the vehicle is specified. That is, the lateral directions of the outer side and the inner side in the vehicle width direction are respectively specified for the tire 1. Figure 1In the embodiment, the tire 1 is mounted on the vehicle in such a manner that the right side is the outer side (OUT side) in the width direction of the vehicle and the left side is the inner side (IN side) in the width direction of the vehicle. Regarding the tire 1, when it is used for the right wheel of the vehicle and when it is used for the left wheel, the main rotation direction and the left-right direction of the tire 1 are opposite, and a tire 1 common to the left and right wheels may be used.

[0037] The tread portion 10 has: a plurality of circumferential grooves 20, 21, 22; and a plurality of lug grooves 25, 26, which extend while curving from a first side, i.e., the left side, to a second side, i.e., the right side, in the tire width direction. The tread portion 10 includes a plurality of pattern blocks, which are divided by the plurality of circumferential grooves 20, 21, 22 and the plurality of lug grooves 25, 26, and are separated in the tire circumferential direction and in the tire width direction.

[0038] The pattern block is an island-shaped area that rises toward the outer side of the tire radial direction. Figure 2 As shown, the tread portion 10 has a plurality of center blocks 50, a plurality of middle blocks 60, 70, and a plurality of shoulder blocks 80, 90, which will be described later, as the pattern blocks. The tire equator CL, which will be described later, passes through the center block 50. The middle block 60 and the shoulder block 80 are arranged on the left side in the width direction of the tread portion 10, and the middle block 70 and the shoulder block 90 are arranged on the right side in the width direction of the tread portion 10.

[0039] The plurality of circumferential grooves 20, 21, 22 include: a first circumferential groove 20 formed near the center in the width direction of the tread portion 10; and a second circumferential groove 21 and a third circumferential groove 22 provided on the left and right sides of the first circumferential groove 20. In addition, a plurality of inclined circumferential grooves 31 described later are formed between the first circumferential groove 20 and the second circumferential groove 21 of the tread portion 10. The "tire width direction" and the "width direction of the tread portion 10" are the same direction, and the two expressions are used appropriately below.

[0040] The first circumferential groove 20 and the second circumferential groove 21 are arranged across the center of the tire width direction. Among the plurality of circumferential grooves 20, 21, 22, the first circumferential groove 20 is arranged closest to the tire equator CL in the center of the tire width direction. The tire equator CL means a line passing through the center of the tire width direction along the tire circumference.

[0041] In addition, the tread portion 10 is provided with a central region 40 which is a predetermined region in the tire width direction divided by the first circumferential groove 20 and the second circumferential groove 21. The central region 40 is divided into a central block 50 and an intermediate block 60 which are separately arranged on the left and right sides by a plurality of inclined circumferential grooves 31 described later at a plurality of positions in the tire circumferential direction. The central block 50 is arranged adjacent to the central side of the first circumferential groove 20 in the tire width direction. The central block 50 corresponds to the first land portion which is a central land portion. A central block row 41 is formed by a plurality of central blocks 50 arranged in the tire circumferential direction.

[0042] The middle block 60 corresponds to the second land portion. The middle block row 44 is formed by a plurality of middle blocks 60 arranged in the tire circumferential direction.

[0043] In addition, a shoulder block row 45 including a plurality of shoulder blocks 80 whose inner ends in the tire width direction are determined by the second circumferential groove 21 is formed in the tread portion 10. In addition, an intermediate block row 46 including a plurality of intermediate blocks 70 divided by the first circumferential groove 20 and the third circumferential groove 22 is formed in the tread portion 10. In addition, a shoulder block row 47 including a plurality of shoulder blocks 90 whose inner ends in the tire width direction are determined by the third circumferential groove 22 is formed in the tread portion 10. The shoulder block 80 is equivalent to the third land portion as the shoulder land portion. The intermediate block 70 is equivalent to the fourth land portion. The shoulder block 90 is equivalent to the fifth land portion as the shoulder land portion. The circumferential grooves 20, 21, 22 are substantially the same in width along the tire circumferential direction.

[0044] The plurality of transverse grooves 25, 26 extend from the left side to the right side in the tire width direction while being curved, and are arranged at intervals from each other in the tire circumferential direction. The plurality of transverse grooves 25, 26 are inclined toward the same side relative to the tire width direction between adjacent blocks in the tire circumferential direction in the plurality of block rows 41, 44 to 47. The transverse grooves 25, 26 in the central block row 41 and the middle block row 44 are more inclined relative to the tire width direction than the transverse grooves 25, 26 in the other block rows 45 to 47. As a result, it is easy to achieve improved snow traction performance in the lateral direction in the central portion in the tire width direction. In addition, the plurality of transverse grooves 25, 26 are shallower in depth than each of the plurality of circumferential grooves 20 to 22.

[0045] Furthermore, the plurality of lug grooves 25 and 26 include a plurality of first lug grooves 25 and a plurality of second lug grooves 26 separated in the tire circumferential direction. In the tread portion 10, one or more first lug grooves 25 and second lug grooves 26 are alternately arranged in the tire circumferential direction. Hereinafter, a case where the first lug grooves 25 and the second lug grooves 26 are alternately arranged one by one in the tread portion 10 and in the tire circumferential direction is described, but a plurality of first lug grooves 25 may be alternately arranged with one second lug groove 26, respectively. The first lug groove 25 is a lug groove that crosses the tire circumferential direction from the middle portion of the inclined circumferential groove 31 described later in the central region 40. On the other hand, the second lug groove 26 is a lug groove that connects two second lug grooves 26 from both ends of the inclined circumferential groove 21. The widths of the respective lug grooves 25 and 26 are substantially the same, but the first circumferential groove 20 side end of each lug groove 25 and 26 in the middle block row 46 is thinner than the other portions.

[0046] In the present embodiment, the same type of pattern blocks marked with the same reference numerals are arranged in a row along the tire circumferential direction. In addition, the same number of pattern blocks are separated at multiple positions in the tire circumferential direction and arranged along the multiple lug grooves 25 and 26 of the tread portion 10. That is, the same number of central pattern blocks 50, middle pattern blocks 60 and 70, and shoulder pattern blocks 80 and 90 are formed in the tread portion 10.

[0047] A plurality of thin linear sipes extending approximately in the tire width direction or approximately in the tire circumferential direction are formed on the contact surface of each pattern block. Each sipe is a thin linear groove having a width thinner than the circumferential grooves 20 to 22 and the transverse grooves 25 and 26, which can improve the edge effect of hooking on snow and ice, and can achieve good braking drivability and handling stability on icy and snowy roads. The tire 1 having such a tread pattern is suitable for all-season tires, for example.

[0048] The tire 1 has sidewall portions 12 formed in an annular shape along the tire circumferential direction similarly to the tread portion 10 , on both sides in the width direction of the tread portion 10 .

[0049] On the other hand, the shoulder blocks 80 and 90 arranged at both ends in the width direction of the tread portion 10 include the ground contact edge T ( Figure 2 The end of each shoulder pattern block 80, 90 in the tire width direction is exposed further outward in the tire width direction than the ground contact end T, and the outer peripheral surface is gently curved inward in the tire radial direction in a manner that bulges outward. The portion of each shoulder pattern block 80, 90 that is exposed further outward in the tire width direction than the ground contact end T is called a buttress.

[0050] In this specification, the ground contact edge T refers to the two ends in the tire width direction of the portion that contacts a flat road surface when a load of 70% of the regular load (maximum load capacity) at the regular internal pressure is applied when an unused tire 1 is mounted on a regular rim and filled with air to reach the regular internal pressure.

[0051] Here, the "regular rim" is a rim determined according to the tire specifications. If it is a JATMA specification, it is a "measurement rim", if it is a TRA specification, it is a "design rim", and if it is an ETRTO specification, it is a "measurement rim". Regarding the "regular internal pressure", if it is a JATMA specification, it is the "maximum air pressure", if it is a TRA specification, it is the maximum value recorded in the table "Tire load limit at various cold inflation pressures", and if it is an ETRTO specification, it is the "inflation pressure". Regarding the "regular load", if it is a JATMA specification, it is the "maximum load capacity", if it is a TRA specification, it is the maximum value recorded in the table "Tire load limit at various cold inflation pressures", and if it is an ETRTO specification, it is the "load capacity".

[0052] A reinforcement structure (not shown) is provided on the inner circumference of the tire 1. The reinforcement structure includes: a carcass portion, which is a cord layer covered with rubber; and a belt, which is arranged between the tread pattern and the carcass portion. The carcass portion is composed of, for example, two layers of carcass cords, forming a tire skeleton that withstands loads, impacts, air pressure, etc. The belt is a reinforcement belt extending along the circumferential direction of the tire, which strongly tightens the carcass portion and improves the rigidity of the tread portion 10. A rubber layer, i.e., an inner liner, is attached to the inner circumference of the carcass portion to maintain air pressure.

[0053] In addition, the tire 1 is provided with a bead portion 13, which is provided to be connected to the inner peripheral end of the sidewall portion 12 and is curved in a manner extending inwardly in the tire radial direction and convexly toward the inner side of the tire 1. The bead portion 13 is located at a position closer to the inner side (the tire equator CL side) in the width direction of the tire 1 than the sidewall portion 12. The bead portion 13 is a portion fixed to the rim of the wheel, and a bead core and a bead outer rubber are provided inside.

[0054] Furthermore, in the embodiment, inclined circumferential grooves 31 are formed at a plurality of locations in the tire circumferential direction in the central region 40. The inclined circumferential grooves 31 improve the snow traction performance of the tire 1. The inclined circumferential grooves 31 will be described in detail later.

[0055] And, if Figure 2As shown, bridge portions 100, 101 as protrusions are formed in the lug grooves 25, 26 between the center blocks 50 in the center block row 41. The bridge portions 100, 101 improve the rigidity of the center blocks 50 adjacent in the tire circumferential direction. Protrusions 102, 103, 104, 105 are also provided in the lug grooves 25, 26 between the blocks of the middle block row 44, the shoulder block row 45, the middle block row 46, and the shoulder block row 47. The protrusions 102 to 105 improve the rigidity of the blocks adjacent in the tire circumferential direction.

[0056] Furthermore, tapered surfaces that are inclined so as to decrease toward the corresponding ends are formed at both ends of the bridge portion 100 of the second lug groove 26 formed between the center blocks 50. As described below, the rigidity of the center block 50 can be improved, and the influence in the tire rotation direction can be suppressed, and the reduction in drainage performance in the center portion in the tire width direction can be suppressed.

[0057] In addition, two protrusions 106 and 107 are formed as first protrusions at the groove bottom of the second circumferential groove 21 and at both sides of the second circumferential groove 21 side ends of the lug grooves 25 and 26 between the shoulder blocks 80 of the shoulder block row 45. In addition, a protrusion 108 is formed as a third protrusion at the groove bottom of the intersection of the second circumferential groove 21 and the extension of the lug grooves 25 and 26 and in the portion surrounded in three directions by the two protrusions 106 and 107 and the protrusion 103 as the second protrusion. As described later, the snow traction performance can be improved and the rolling resistance can be reduced, and the air pumping sound can be reduced.

[0058] In addition, thin grooves 109 and 110 described later are formed in the portion of the shoulder block 90 that is closer to the tire width direction outside than the ground contact end T. This can improve the snow traction performance. In addition, the thin grooves 109 and 110 are connected to the sipes 81 and 82 that are transverse sipes, and are not connected to the lug grooves 25 and 26, so that drainage can be improved and the rigidity of the shoulder block 90 can be improved.

[0059] Next, the structures of the inclined circumferential groove 31, the first circumferential groove 20 side portion of the second lug groove 26, the connecting portion of the first circumferential groove 20, the second and third circumferential grooves 21, 22 and the lug grooves 25, 26, and the fine grooves 109, 110 of the shoulder block 90 are described in detail. Figure 3 to Figure 6 The inclined circumferential groove 31 will be described.

[0060] Figure 3 It is a plan view showing a part of the central region 40 of the tread portion 10 in an enlarged manner. Figure 4 yes Figure 3 An enlarged perspective view of the recessed portion 31a of the inclined circumferential groove 31. Figure 5 It is a plan view showing the recessed portion 31 a in an enlarged manner. Figure 6 It is shown Figure 5 Figure 2 is a cross-section of the A1-A1 line in FIG.

[0061] The inclined circumferential grooves 31 are provided at a plurality of positions in the tire circumferential direction in the central region 40. Each inclined circumferential groove 31 is a groove that crosses the first lug groove 25 in the tire circumferential direction and is inclined relative to the tire circumferential direction in such a manner that the first end K1 in the longitudinal direction is closer to the tire equator CL in the center of the tire width direction than the second end K2 in the longitudinal direction. The inclined circumferential groove 31 crosses the first lug groove 25 and connects two second lug grooves 26.

[0062] At a position where the first end K1 of the inclined circumferential groove 31 penetrates the second lug groove 26, a wall surface 50a ( Figure 5 The recessed portion 31a is: extending along the second lug groove 26, and has a shape when viewed from the outside of the tire radial direction, that is, in a top view, Figure 5 As shown, it is a portion that is substantially isosceles triangle and is more recessed than the ground contact surface of the center block 50 .

[0063] More specifically, the shape of the concave portion 31a when viewed from above is a shape in which one corner corresponding to the vertex P1 of 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 is rounded. The lengths of the first long side L1 and the second long side L2 are substantially the same and are greater than the length of the short side L3. The first long side L1 is along the length direction of the second lug groove 26. In addition, the vertex P1 of the isosceles triangle as the intersection of the second long side L2 and the short side L3 is further inward than the wall surface 50a. In addition, the vertices P1 and P3 are located at a position farther away from the tire equator CL in the center of the tire width direction than the vertex P2 of the isosceles triangle as the intersection of the first long side L1 and the second long side L2. One corner corresponding to the vertex P1 of the isosceles triangle is located at the intersection of the two long sides L2 and the short side L3.

[0064] Furthermore, an inclined surface 31b is formed on the bottom surface of the recessed portion 31a so as to be closer to the contact surface 50b of the central block 50 and to the inner side of the central block 50. Figure 4 As shown in FIG. 1 , the bottom surface of the recess 31a is inclined near the left end of the lower edge DL adjacent to the second lug groove 26 so as to slightly approach the contact surface toward the left end of the recess 31a. Furthermore, the left end of the recess 31a is slightly recessed toward the inner side of the center block 50, and an inclined surface 31b is formed so as to connect the upper edge UL and the lower edge DL on the contact surface 50b. As a result, as shown in FIG. Figure 6As shown in the cross-sectional view of FIG. 1 , the cross section of the bottom surface of the recessed portion 31a is formed to be directed toward the inner side ( Figure 6 The center block 50 is formed so as to be straightly inclined so as to be close to the contact surface 50b of the center block 50 (left side). Therefore, a large space is formed inside the recessed portion 31a recessed from the wall surface 50a of the center block 50, into which water can flow from the second lug groove 26 and the inclined circumferential groove 31. In addition, in this specification, when the words "upper" and "lower" are used, the side of the raised part such as the block and the protrusion that rises in the raised direction is referred to as "upper", and the side that falls is referred to as "lower".

[0065] Although not shown in the figure, even in Figure 5 The A2-A2 line section and the A3-A3 line section are also Figure 6 Similarly, the cross section of the bottom surface of the recessed portion 31 a is formed in a straight line shape that is inclined linearly toward the inner side of the center block 50 and approaches the ground contact surface 50 b of the center block 50 .

[0066] Moreover, if Figure 2 As shown, the plurality of inclined circumferential grooves 31 are formed in a zigzag shape by connecting a portion of the second lug grooves 26 formed at a plurality of positions in the tire circumferential direction. Figure 4 As shown, the portion of each inclined circumferential groove 31 excluding the recessed portion 31a is deeper than the portion of each lug groove 25, 26 excluding the intersection portion intersecting the inclined circumferential groove 31. The depth of the portion of the inclined circumferential groove 31 excluding the recessed portion 31a can be set to be substantially the same as the depth of each lug groove 25, 26.

[0067] Thus, an inclined circumferential groove 31 is formed which crosses the first lug groove 25 provided in the central area 40 of the tread portion 10 and is inclined relative to the tire circumferential direction. In addition, the recessed portion 31a provided at the first end K1 of the inclined circumferential groove 31 enters the central pattern block 50, and the first end K1 is closer to the tire equator CL in the center of the tire width direction than the second end K2. Therefore, the handling stability and cornering performance of the vehicle on snow can be improved. For example, the portion other than the recessed portion 31a of the inclined circumferential groove 31 is inclined relative to the tire circumferential direction, so that snow and ice are easily caught and clamped in the circumferential and lateral directions of the tire. In addition, the portion of the left end of the recessed portion 31a of the inclined circumferential groove 31 close to the center of the tire width direction is easily caught and clamped in the lateral direction of the tire 1. Thus, the snow traction performance of the tire 1 in the circumferential and lateral directions can be improved. Furthermore, the first end K1 of the inclined circumferential groove 31 having the recessed portion 31a is closer to the tire widthwise center than the second end K2, thereby improving the steering stability and cornering performance on snow compared to a case where the recessed portions are widely spaced outward in the tire widthwise direction.

[0068] Furthermore, the recessed portion 31a of the inclined circumferential groove 31 disposed at the first end K1 extends along the second transverse groove 26. Thus, when the vehicle is running on a wet road surface, when the tire 1 rotates and causes water to flow from the second end K2 side toward the first end K1 side in the inclined circumferential groove 31, the space between the recessed portion 31a and the road surface is expanded, thereby preventing the wall surface or bottom surface of the recessed portion 31a from blocking the water flow. Furthermore, an inclined surface 31b is formed on the bottom surface of the recessed portion 31a in a manner that tends toward the inner side of the central tread block 50 and approaches the contact surface 50b of the central tread block 50, thereby preventing water from being retained in the recessed portion 31a. Furthermore, as described above, Figure 6 Unlike the case where the inside of the recessed portion 31c is set as a right angle corner as shown by the double-dashed line in the figure, it is possible to suppress the reduction in rigidity of the central pattern block 50. As a result, the drainage performance from the groove of the tire 1 is excellent, so the effect of suppressing hydroplaning is excellent, and the tire 1 in which the reduction in rigidity of the central pattern block 50 can be suppressed can be realized.

[0069] For example, it can be imagined that when the vehicle is running, the tire 1 is facing Figure 3 When rotating in the direction of arrow α, Figure 3 The water flows along the second lug groove 26 from the center in the tire width direction toward the outer side in the tire width direction as shown by the arrow β in FIG. Figure 3 As shown by arrow γ, water flows along the inclined circumferential groove 31 toward the rear side in the rotation direction of the tire 1 merge. In this case, the volume of the space at the merging portion can be expanded by the recessed portion 31a, so the resistance of the water flow can be suppressed and the drainage performance can be improved.

[0070] In addition, regarding the tire 1, the shape of the recessed portion 31a when viewed from above is a shape in which one corner corresponding to the vertex P1 of the isosceles triangle is rounded, so that the turbulence of the water flow inside the recessed portion 31a can be suppressed, and the water flow in the groove connected to the recessed portion 31a can be made smoother to improve drainage. In addition, unlike the case where the shape of the recessed portion 31a when viewed from above is set to a rectangular shape, the resistance of the water flow at the confluence of the water flow can be suppressed, and the recessed portion 31a can be prevented from being excessively enlarged, so that the rigidity of the central pattern block 50 can be suppressed from being reduced.

[0071] Fig. 7A A first example of other examples of the concave portion is shown. Fig. 7A In the structure shown in the figure, the upper end position of the inclined surface 31e formed on the bottom surface of the recessed portion 31d is located further inward in the tire radial direction than the ground contact surface 50b ( Fig. 7A In this structure, Figure 3 to Figure 6 Compared with the case of the structure shown, the rigidity of the center block 50 may be slightly reduced, but since the space in the recessed portion 31a can be expanded, the effect of suppressing hydroplaning can be further improved.

[0072] Figure 7B A second example of another example of a concave portion is shown. Figure 7B In the structure shown, the bottom surface of the recessed portion 31f is formed with: a convex surface 31g with a curved cross section that convexes outwardly so as to approach the contact surface 50b of the central pattern block 50 toward the inner side of the central pattern block 50; and a concave surface 31h with a circular arc cross section that is continuous with the inner end of the convex surface 31g and has rounded corners. Figure 3 to Figure 6 Compared with the structure shown in the figure, the rigidity of the central block 50 may be slightly reduced, but since the space in the recess 31a can be expanded, the hydroplaning suppression effect can be improved. In addition, the water flow between the recess 31a and the groove can be smoothed to achieve improved drainage.

[0073] Figure 8 A third example of another example of a concave portion is shown. Figure 8 In the structure shown, Figure 3 to Figure 6 Unlike the structure shown in the figure, the shape of the concave portion 31i in a plan view is a shape in which each corner of the isosceles triangle is not rounded, and an inclined surface 31j is formed on the bottom surface of the concave portion 31a in such a manner that the second long side L2 connecting the vertex P1 and the vertex P2 is set as the upper edge UL, and the upper edge UL is connected to the lower edge DL on the bottom surface side of the groove. In the case of this structure, since the area of ​​the wall surface 31k at the left end of the concave portion 31i can be expanded, the lateral snow traction performance can be further improved.

[0074] Next, use Figures 9 to 14 The first circumferential groove 20 side portion of the second lug groove 26 and the structure of the first circumferential groove 20 will be described in detail. Fig. 9 It is a plan view showing a part of the central region 40 of the tread portion 10 in an enlarged manner. Fig.10 It is enlarged to show Fig. 9 A three-dimensional view of the connecting portion of the first circumferential groove 20 and the second lug groove 26 between the central pattern block 50. Fig.11 BB line pair Fig. 9 An enlarged perspective view showing a cutaway view. Fig.12 It is enlarged to show Fig. 9 Top view of section C. Fig.13 It is shown Fig.12 Figure 2. DD line cross section of FIG. Fig.14 yes Fig. 9 Enlarged view of the EE line cross section.

[0075] like Figures 9 to 14As shown in FIG. 1 , a plurality of central blocks 50 are arranged adjacent to each other on the central side of the first circumferential groove 20 in the tire width direction. The lug grooves 25 and 26 between the central blocks 50 extend to the right side in the tire width direction and open to the first circumferential groove 20. A bridge portion 100 with a raised bottom surface is formed on the first circumferential groove 20 side portion of the second lug groove 26 between the central blocks 50. Fig.12 In FIG. 1 , the bridge portion 100 is shown by a sand-like portion.

[0076] The bridge portion 100 is provided to improve the rigidity of the adjacent central pattern blocks 50. Fig.12 , Fig.13 As shown, the cross section of the bridge portion 100 is roughly trapezoidal. Specifically, the bridge portion 100 has an upper surface 100a that is approximately flat along the tire circumference and has tapered surfaces 100b and 100c that are inclined in such a way that the side ends of the central side ends of the second lug groove 26 in the longitudinal direction and the side ends of the first circumferential groove 20 are respectively lowered toward the corresponding ends in the longitudinal direction of the bridge portion 100. Fig.12 In FIG. 1 , arrows J1 and J2 shown on the side surfaces of the bridge portion 100 indicate that the corresponding side surfaces are inclined in a direction decreasing from the upper surface toward the front end of the arrows.

[0077] The second lug groove 26 has a wide portion 111 formed therein. The wide portion 111 is formed at the side end of the first circumferential groove 20 and at the Fig.12 The tire circumferential range W is formed as a substantially triangular space in a plan view, the width of which is larger on the first circumferential groove 20 side than on the lug groove center side. The tapered surface 100c of the bridge portion 100 on the first circumferential groove 20 side is provided in the wide portion 111.

[0078] like Fig.10 As shown, the end of the bridge portion 100 in the width direction is connected to the wall surface of the central pattern block 50 by means of a chamfered portion 123 having an arc-shaped cross section. On the other hand, the end of the bridge portion 100 in the width direction may also be formed into a structure that is directly connected to the wall surface without the chamfered portion. Fig.13 As shown, the maximum height HB of the bridge portion 100 can be set to a range of, for example, 30% to 40% of the depth HL of the second lug groove 26 .

[0079] In addition, although detailed description is omitted, Fig. 9 As shown, a bridge portion 101 with a raised bottom surface is also formed in the middle portion of the first lug groove 25 between the center blocks 50 adjacent to the second lug groove 26. The shape of the bridge portion 101 is also the same as that of the bridge portion 100, and is formed in a trapezoidal shape in cross section with side surfaces at both ends having tapered surfaces that are inclined so as to decrease toward the corresponding ends in the length direction of the bridge portion 101.

[0080] And, if Figures 9 to 11 , Fig.14 As shown, the bottom surface of the first circumferential groove 20 is aligned with the first side ( Fig. 9 The lower side of Fig.10 A conical convex portion 112 is formed adjacent to the left side of the tire. The conical convex portion 112 is generally triangular in plan view and is formed to bulge outward in the tire radial direction. Fig.11 , Fig.14 As shown, on the upper surface of the tapered convex portion 112, a first inclined surface 113 is provided which is higher on the left side of the lug grooves 25 and 26 between the central blocks 50 than on the right side of the middle blocks 70.

[0081] And, if Fig. 9 , Fig.10 As shown, on the second side ( Fig. 9 The upper side of Fig.10 The entire side surface (right side) is formed with a second inclined surface 114 that is inclined toward the wide width portion 111 in the tire width direction and toward the second side in the tire circumferential direction. Fig. 9 As shown, the second inclined surface 114 is substantially along the wall surface 111 a of the wide portion 111 on the tapered convex portion 112 side.

[0082] Furthermore, on the conical convex portion 112, and on the first side ( Fig. 9 The lower side of Fig.10 A third inclined surface 115 is formed on the side surface of the first tread (left side) that is inclined toward the central pattern block 50 in the tire width direction as a whole and toward the second side in the tire circumferential direction. The third inclined surface 115 is arranged adjacent to a position closer to the second side in the tire circumferential direction than the opening of the first circumferential groove 20 side of the first lug groove 25. The third inclined surface 115 is inclined with respect to the tire circumferential direction in a manner that is substantially along the length direction of the first lug groove 25.

[0083] According to the above structure, the bridge portions 100 and 101 are provided in the lug grooves 25 and 26 between the center blocks 50, so that the rigidity of the center blocks 50 can be improved. In addition, when the vehicle is running on a wet road, even if the tire rotates in a direction that causes water to flow from the first circumferential groove 20 close to the center in the tire width direction to the lug grooves 25 and 26 between the center blocks 50, the tapered surface 100c of each bridge portion 100 and 101 makes it easy for water to flow from the first circumferential groove 20 to the lug grooves 25 and 26.

[0084] Specifically, when the tire 1 is Fig. 9 When the bridge portion 100 is rotated in the direction of arrow α, the conical surface 100c ( Fig.12 ) makes the water edge Fig. 9The direction indicated by the arrow M1 in the figure flows from the first circumferential groove 20 to the second lug groove 26. Fig. 9 When the bridge portion 100 is rotated in the opposite direction to the direction of arrow α, the bridge portion 100 can be easily rotated by using the tapered surface 100b ( Fig.12 ) so that water flows from the second transverse groove 26 to the first circumferential groove 20, i.e., along Fig. 9 Thus, a tire 1 can be realized which can improve the rigidity of the center block 50, suppress the influence of the tire rotation direction, and suppress the reduction in drainage performance in the center portion in the tire width direction.

[0085] Furthermore, a conical convex portion 112 is formed on the bottom surface of the first circumferential groove 20, and has a first inclined surface 113 higher on the side of the lug grooves 25 and 26 between the central pattern blocks 50 on the upper surface, so that when the tire 1 is turned toward Fig. 9 When the tire rotates in the direction of arrow α, water can more easily flow along the first inclined surface 113 from the first circumferential groove 20 to the second lug groove 26 between the center blocks 50. This can further suppress the reduction in drainage performance in the tire width direction center portion.

[0086] Furthermore, a wide portion 111 is formed at the side end of the first circumferential groove 20 of the second lug groove 26, a tapered convex portion 112 is arranged adjacent to the first side of the wide portion 111 in the tire circumferential direction, and a second inclined surface 114 is formed on the side surface of the tapered convex portion 112 on the second side in the tire circumferential direction. Fig. 9 When rotating in the direction opposite to the direction of arrow α in the figure, regardless of the presence or absence of the tapered convex portion 112, the inclination of the first inclined surface 113 and the inclination of the second inclined surface 114 of the tapered convex portion 112 can enable the water flowing from the second transverse groove 26 into the first circumferential groove 20 to flow more toward the first circumferential groove 20 through the right side of the first circumferential groove 20 in the tire width direction for drainage.

[0087] Furthermore, a third inclined surface 115 is formed on the side surface of the first side of the conical convex portion 112 in the tire circumferential direction. The third inclined surface 115 is inclined relative to the tire circumferential direction in a manner along the length direction of the first lug groove 25. Fig. 9 When the tire rotates in the direction of arrow α, the third inclined surface 115 of the tapered convex portion 112 facilitates water to flow from the first circumferential groove 20 to the first lug groove 25. Therefore, it is possible to further suppress a reduction in drainage performance in the tire width direction center portion.

[0088] In this example, the rigidity of the center blocks 50 on both sides of the tire circumferential direction can be improved by using the bridge portion 101 having a trapezoidal cross section provided in the middle of the first lug groove 25 between the center blocks 50. In addition, similarly to the bridge portion 100, the drainage performance from the first circumferential groove 20 to the first lug groove 25 can be improved.

[0089] Next, the structures of the connection portions between the second and third circumferential grooves 21 and 22 and the lug grooves will be described in detail. Fig.15 In one example of implementation, FF line pairs are used. Fig. 9 An enlarged perspective view showing a cutaway view. Fig.16 It is shown Fig. 9 FIG. 1 is an enlarged cross-sectional view of the second protrusion of the G portion, namely the protrusion 103 . Fig.17 yes Fig.15 Magnified view of the HH line cross section.

[0090] Refer to the above Fig. 9 and Fig.15 In the second circumferential groove 21, at the groove bottoms on both sides of the side ends of the second circumferential groove 21 of each lug groove 25, 26, two protrusions 106, 107 as first protrusions are formed corresponding to each lug groove 25, 26. Each protrusion 106, 107 is formed to bulge outward in the tire radial direction. Fig. 9 As shown, the shape of each protrusion 106, 017 in a plan view is a substantially triangular shape whose base is connected to the wall surface of the shoulder block 80 and whose vertex is connected to the wall surface on the middle block 60 side.

[0091] And, if Fig.15 , Fig.16 As shown in FIG. 1 , the upper surface of each protrusion 106, 107 is formed as an inclined surface S that is inclined in a manner that rises toward the outer side of the tire radial direction toward the shoulder pattern block 80. Thus, when the vehicle is running on a wet road, the tire 1 is inclined toward the outer side of the tire 1. Fig. 9 When the tire rotates in the direction of arrow α in the tread or in the opposite direction of arrow α, the inclined surface S of each protrusion 106, 107 can easily make water flow from the second circumferential groove 21 to the lug grooves 25, 26 between the shoulder blocks 80. Therefore, as described later, even when the lug grooves 25, 26 are provided with the protrusion 103 as the second protrusion, the drainage performance can be improved.

[0092] Specifically, if Fig. 9 , Fig.16As shown in the figure, a protrusion 103 that bulges outward in the tire radial direction is provided at the groove bottom of each lug groove 25, 26 between the shoulder blocks 80 on the side of the second circumferential groove 21. Like the bridges 100, 101 provided on the lug grooves 25, 26 between the center blocks 50, the cross section of the protrusion 103 is roughly trapezoidal. Specifically, the upper surface of the protrusion 103 is approximately flat along the tire circumferential direction, and has two tapered surfaces 103a, 103b that are inclined in a manner that the side surfaces on both sides of the longitudinal direction of the lug grooves 25, 26 are respectively lowered toward the corresponding ends of the protrusion 103. The protrusion 103 is provided in order to improve the rigidity of the shoulder block 80, and both ends of the protrusion 103 in the width direction are connected to the wall surface of the shoulder block 80 adjacent in the tire circumferential direction.

[0093] As described above, the upper surfaces of the protrusions 106 and 107 in the second circumferential groove 21 are formed with inclined surfaces S. Therefore, when the vehicle travels on a wet road, water can easily flow from the second circumferential groove 21 to the lug grooves 25 and 26, regardless of the presence or absence of the bridge portion 100, thereby improving drainage.

[0094] On the other hand, when the two protrusions 106 and 107 are formed in the second circumferential groove 21 and the protrusions 103 are provided in the lug grooves 25 and 26, if the space of the intersection of the second circumferential groove 21 and the extension of the lug grooves 25 and 26 is large, air is likely to be retained in the space. Therefore, when a vehicle equipped with the tire 1 runs on a dry road, air pumping sound is likely to be generated by the air retained in the space of the above-mentioned intersection.

[0095] In this case, in order to eliminate this undesirable situation, such as Fig. 9 , Fig.15 , Fig.17 As shown in FIG. 1 , a protrusion 108 as a third protrusion is formed at the groove bottom of the portion of the second circumferential groove 21 that intersects the extended portions of the lug grooves 25 and 26, which is surrounded in three directions by the two protrusions 106 and 107 and the protrusion 103. The protrusion 108 uses the lowest portion of the second circumferential groove 21 as a reference surface 21a ( Fig.15 , Fig.17 ) and bulges radially outward in a manner higher than the reference surface 21a.

[0096] exist Fig. 9 In the figure, the protrusion 108 is represented by the portion marked as the sand-like portion in the second circumferential groove 21. Fig. 9 As shown, the protrusion 108 is substantially trapezoidal in plan view, and both end edges in the tire circumferential direction are connected to the wall surfaces of the two protrusions 106 and 107 on both sides at the ends in the tire circumferential direction.

[0097] In addition, if Fig.17As shown in FIG. 1 , the upper surface of the protrusion 108 is formed into a substantially flat surface with a constant height in the vertical direction relative to the reference surface 21a. Both end edges of the protrusion 108 in the tire width direction are connected to the wall surface of the second circumferential groove 21. Fig.15 As shown, the upper surface of the protrusion 108 is lower than the upper surfaces of the protrusions 106 and 107. In this example, the lowest ends of the inclined surfaces S of the protrusions 106 and 107 are substantially aligned with the height position of the upper surface of the protrusion 108.

[0098] And, if Fig. 9 As shown, the side ends of the second circumferential grooves 21 of the lug grooves 25, 26 between the shoulder blocks 80 are opposite to the wall surface of the end in the tire width direction of the middle block 60 on the extension line of the lug grooves 25, 26, separated by the part of the second circumferential groove 21 where the protrusion 108 is set at the groove bottom.

[0099] According to the above structure, two protrusions 106 and 107 are formed at the groove bottom of the second circumferential groove 21 and at both sides of the second circumferential groove 21 side ends of the lug grooves 25 and 26. In addition, the protrusion 103 is formed at the groove bottom of the second circumferential groove 21 side portion of the lug grooves 25 and 26. As a result, the rigidity of the shoulder block 80 adjacent to the protrusions 106 and 107 of the second circumferential groove 21 and the shoulder block 80 adjacent to the protrusions 103 of the lug grooves 25 and 26 can be improved. Therefore, the rigidity of the shoulder block 80 can be improved by one of the protrusions 106 and 107 and the protrusion 103. Therefore, the energy loss caused by the deformation of the block during the vehicle running can be reduced, and thus the rolling resistance of the tire 1 can be reduced. In addition, the shear force acting on the snow compacted in the groove when running on the snowy road surface can be used to increase the resistance between the tire 1 and the road surface, thereby improving the snow traction performance.

[0100] Furthermore, at the intersection of the second circumferential groove 21 and the extension of the lug grooves 25 and 26 between the shoulder blocks 80, a protrusion 108 is formed at the groove bottom of the portion surrounded in three directions by the two protrusions 106 and 107 and the protrusion 103. As a result, the volume of the space at the intersection is reduced, so the amount of trapped air can be reduced. Therefore, the air pumping sound during running can be reduced.

[0101] Furthermore, the side ends of the second circumferential grooves 21 of the lug grooves 25 and 26 between the shoulder blocks 80 are opposite to the wall surface of the middle block 60 on the extension lines of the lug grooves 25 and 26, across the portion of the second circumferential grooves 21 where the protrusions 108 are provided at the groove bottom. Thus, the above-mentioned intersection of the second circumferential grooves 21 is surrounded in four directions by the three protrusions 106, 107, and 108 and the wall surface of the middle block 60. Therefore, although it tends to be more difficult to discharge the air at the intersection when the vehicle is running, the amount of trapped air can be reduced in the protrusions 108, so the effect brought by providing the protrusions 108 is more significant.

[0102] In addition, in this example, Fig. 9 As shown in the figure, two protrusions 116 and 117 having a substantially triangular shape in a plan view are also formed at the groove bottom of the third circumferential groove 22 and at both sides of the third circumferential groove 22 side ends of the lug grooves 25 and 26 between the shoulder blocks 90. In addition, a protrusion 105 is formed at the groove bottom on the third circumferential groove 22 side of the lug grooves 25 and 26 between the shoulder blocks 90. The protrusion 105 has a tapered surface that decreases toward the end only on the side surface of the central side end in the longitudinal direction of the lug grooves 25 and 26, and the side end of the third circumferential groove 22 is consistent with the wall surface of the third circumferential groove 22, and no tapered surface is formed.

[0103] Furthermore, at the intersection of the third circumferential groove 22 and the extension of the lug grooves 25 and 26 between the shoulder blocks 90, a protrusion 118 is formed at the groove bottom of the portion surrounded in three directions by the three protrusions 116, 117, and 105. Fig. 9 In FIG. 1 , the portion marked as a sandy area in the third circumferential groove 22 represents the protrusion 118 .

[0104] Fig.18 FIG. 2 is an enlarged cross-sectional view of the protrusion 118 of the third circumferential groove 22. Fig.18 As shown, the upper surface of the protrusion 118 is also formed into a substantially flat surface with a constant vertical height relative to the reference surface 22a of the third circumferential groove 22, similarly to the protrusion 108 in the second circumferential groove 21. Both end edges of the protrusion 118 in the tire width direction are connected to the wall surface of the second circumferential groove 21.

[0105] Thus, the amount of trapped air in the intersection of the third circumferential groove 22 and the extension of the lug groove between the shoulder blocks 90 can also be reduced. Therefore, the air pumping sound during driving can be reduced. Fig. 9As shown, at this intersection, unlike the intersection of the second circumferential groove 21, the second circumferential groove 21 side end of the lug groove between the shoulder pattern blocks 90 and the second circumferential groove 21 side end of the lug groove between the middle pattern blocks 70 are opposite to each other on the extension line of the lug groove. Therefore, at the intersection of the third circumferential groove 22, it is easier to discharge air than at the intersection of the second circumferential groove 21. The effect of providing the protrusion 108 is higher at the intersection of the second circumferential groove 21.

[0106] Fig.19 is a diagram showing another example of the third protrusion. Fig. 9 The corresponding figure of part I. Fig.19 The protrusion 119 shown as the third protrusion is in the shape of a thin line extending in the tire width direction when viewed from above, and its two ends in the tire circumferential direction are not connected to the wall surfaces of the two protrusions 106 and 107. Fig. 9 The effect of the protrusion 108 is relatively poor, but since the volume of the space of the intersection portion of the second circumferential groove 21 intersecting with the extension of the lug grooves 25 and 26 between the shoulder blocks 80 can be reduced, the effect of reducing the air pumping sound during running can be achieved. In this way, the following structure can be formed: the intersection portion of the circumferential groove intersecting with the extension of the lug groove is formed only at a part of the groove bottom of the portion surrounded by the two first protrusions and the second protrusion in three directions.

[0107] Next, use Figures 20-22 The narrow grooves 109 and 110 of the shoulder block 90 will be described. Fig. 20 It is enlarged to show Figure 2 FIG. 9 is a diagram of a portion of a shoulder block 90 . Fig.21 It is an enlarged perspective view of the outer end portion of the shoulder block 90 in the tire width direction. Fig. 22 This is a perspective view showing the shoulder block 90 cut along a plane including the ground contact end T.

[0108] A plurality of lug grooves 25, 26 are formed between the plurality of shoulder blocks 90 of the shoulder block row 47, which are separated in the tire circumferential direction and extend from the left side to the right side in the tire width direction. The plurality of shoulder blocks 90 are divided 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 portions located on the outer side in the vehicle width direction.

[0109] Two sipes 81, 82 as transverse sipes 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, 82 is provided between two lug grooves 25, 26 adjacent in the tire circumferential direction. In the shoulder block 90, the width of each sipe 81, 82 is the same in the entire length direction and is smaller than the maximum width of the two lug grooves 25, 26 provided at both sides of the sipe 81, 82.

[0110] The end portions 81a and 82a of each sipe 81 and 82, which are the inner ends in the tire width direction, open on the wall surface of the inner end in the tire width direction of the shoulder pattern block 90. ​​The end portions 81b and 82b of each sipe 81 and 82, which are the outer ends in the tire width direction, terminate in the shoulder pattern block 90 and do not open on the wall surface of the shoulder pattern block 90. ​​A meandering extension portion is provided in a part of the sipes 81 and 82, but the meandering extension portion may be omitted.

[0111] Furthermore, two narrow grooves 109 and 110 are formed between the two lug grooves 25 and 26 sandwiching the sipes 81 and 82 in the shoulder block row 47, that is, at a position further outward in the tire width direction than the ground contact end T of the upper surface of the shoulder block 90. ​​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.

[0112] The narrow groove 110 and the narrow groove 109 are oriented outward in the tire width direction and are inclined toward the same side with respect to the tire circumferential direction. The narrow groove 110 has its inner end in the tire width direction branched from the vicinity of the outer end of the sipe 82 in the tire width direction and connected to the sipe 82 .

[0113] The depth of each narrow groove 109, 110 is shallower than that of each sipe 81, 82, and the width increases toward the opening end in a circular arc cross section, for example. The shape of the narrow groove is not limited thereto, and may be formed in a shape in which the width increases from the upper end to the opening end in a substantially rectangular cross section, or in a substantially flat bottom surface, and the wall surfaces on both sides in the width direction are inclined relative to the bottom surface.

[0114] Each of the narrow grooves 109 and 110 is separated from the two lug grooves 25 and 26 at both ends of the shoulder block 90 in the tire circumferential direction over the entire length thereof.

[0115] Furthermore, the outer ends of the narrow grooves 109 and 110 in the tire width direction do not open on the wall surface of the shoulder block 90, but terminate in the shoulder block 90. ​​Therefore, the narrow grooves 109 and 110 do not open on the wall surface of the shoulder block 90.

[0116] Furthermore, a J-shaped shallow groove 120 is formed in a plan view at a position located outside the tire width direction than the ground contact end T of the upper surface of each shoulder block 90 and at a portion located outside the tire width direction than each narrow groove 109, 110. The straight portion 121 of the shallow groove 120 is located outside the tire width direction than the curved portion 122 and along the tire circumferential direction. The depth of the shallow groove 120 is substantially the same as that of the narrow grooves 109, 110. The width of the shallow groove 120 increases from the end on the curved portion 122 side of both ends in the longitudinal direction toward the end on the straight portion 121 side.

[0117] According to the above structure, narrow grooves 109 and 110 inclined with respect to the tire circumferential direction are formed in the area called buttress on the outer side in the tire width direction of the shoulder block 90 relative to the ground contact end T. In addition, the narrow grooves 109 and 110 are not connected to the sipes 81 and 82 and the two lug grooves 25 and 26 on both sides of the narrow grooves 109 and 110. As a result, the rigidity of the buttress can be increased, and the snow traction performance can be improved.

[0118] Furthermore, the narrow grooves 109 and 110 are connected to the sipes 81 and 82, so that drainage can be improved. Furthermore, the narrow grooves 109 and 110 are inclined toward the same side with respect to the tire circumferential direction over the entire length, so that the sipes 81 and 82, which are easy to improve the drainage of the narrow grooves 109 and 110 and easy to increase in depth, can be extended. Thus, the drainage of the shoulder block 90 can be improved.

[0119] Furthermore, the depth of the narrow grooves 109 and 110 is shallower than that of the sipes 81 and 82. Therefore, although the thickness of the rubber portion of the tire is smaller at the buttresses at the outer ends in the tire width direction, the thickness of the bottom of the narrow grooves 109 and 110 can be prevented from becoming too small by making the narrow grooves 109 and 110 shallower. Thus, it is possible to suppress the occurrence of cracks at the groove bottom of each narrow groove 109 and 110. In particular, the buttresses are easily exposed to sunlight and the rubber hardens, but even in this case, the occurrence of cracks is easily suppressed. Thus, the effect of making the narrow grooves 109 and 110 shallower is significant.

[0120] In the above-described embodiment, two narrow grooves are formed in each shoulder block 90 , but only one narrow groove may be formed in each shoulder block, or three or more narrow grooves may be formed in each shoulder block.

[0121] In the above embodiment, the shoulder land portion is described as a plurality of blocks divided by lug grooves in the tire circumferential direction. However, the shoulder land portion may be formed as follows: lug grooves are not formed in the entire tire width direction, and the shoulder land portion is not divided into a plurality of blocks in the tire circumferential direction. Even in this case, a fine groove may be formed at a position further outward in the tire width direction than the ground contact end: the fine groove is inclined with respect to the tire circumferential direction over the entire length and is connected to the transverse sipe, but is not connected to the lug groove.

Claims

1. A pneumatic tire comprising a tread portion, the tread portion having: a circumferential groove; and a lug groove connected to the circumferential groove and extending from a first side toward a second side in a tire width direction, wherein: The pneumatic tire comprises: Two first protrusions are formed in the circumferential groove at the groove bottom at both sides of the circumferential groove side end of the lug groove; a second protrusion formed at the groove bottom of the circumferential groove side portion of the lug groove; as well as The third protrusion, which intersects the extended portion of the lug groove in the circumferential groove, is formed on at least a portion of the groove bottom of the portion surrounded in three directions by the two first protrusions and the second protrusion. The upper surface of each of the two first protrusions has an inclined surface that is inclined so as to rise toward the outer side in the tire radial direction toward the first land portion on the second protrusion side adjacent to the circumferential groove. The shape of each of the two first protrusions when viewed from the outside in the tire radial direction, i.e., in a plan view, is a substantially triangular shape whose base is connected to the wall surface of the first land portion and whose vertex is arranged on the second land portion side opposite to the first land portion across the circumferential groove. Both end edges of the third protrusion in the tire circumferential direction are connected to wall surfaces of the ends of the two first protrusions in the tire circumferential direction on both sides of the third protrusion.

2. The pneumatic tire according to claim 1, wherein: The circumferential groove side end of the lug groove faces a wall surface of an end portion in the tire width direction of the first land portion across a portion of the circumferential groove where the third protrusion is provided on the groove bottom on an extension line of the lug groove.

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