Tire

Abstract

According to the present invention, a circumferential main groove 30 disposed in a tread part 2 has a shoulder main groove 35 and a center main groove 31. A plurality of land parts 20 have a center land part 21 and a middle land part 22. A plurality of groove units 50 are repeatedly disposed in the tire circumferential direction in the middle land part 22, each of the groove units 50 having: a first groove 51 in which an inner end part in the tire width direction communicates with the center main groove 31 and an outer end part in the tire width direction terminates in the middle land part 22; a second groove 52 which extends in the tire circumferential direction and in which an end part communicates with the first groove 51; and a third groove 53 in which an inner end part in the tire width direction communicates with the second groove 52 and an outer end part in the tire width direction communicates with the shoulder main groove 35. A notch part 60 which extends in the tire width direction and of which one end communicates with the center main groove 31 and the other end terminates in the center land part 21 is disposed in the center land part 21. Consequently, it is possible to improve on-ice performance while suppressing a reduction in on-snow performance and wet performance.

Description

Tire

[0001] The present invention relates to a tire.

[0002] Grooves are formed in the tread portion of a tire mounted on a vehicle for the purpose of ensuring various performances according to the usage mode of the tire, and the performance is improved by devising the shape of the grooves. For example, the pneumatic tire described in Patent Document 1 partitions a center rib that continuously extends in the tire circumferential direction between a pair of circumferential main grooves on the center side, and on both sides of the center rib, first cutouts with tips facing the tire indentation side and second cutouts with tips facing the tire kick-out side are alternately arranged along the tire circumferential direction.

[0003] In addition, the tire described in Patent Document 2 has a circumferential groove extending in the tire circumferential direction, a circumferential fine groove extending in the tire circumferential direction, and a plurality of lug grooves extending in the tire width direction, and a block-shaped land portion is partitioned. The circumferential groove and the circumferential fine groove are formed in a zigzag shape having long portions and short portions with relatively different lengths by oscillating in the tire width direction while extending in the tire circumferential direction. Further, the pneumatic tire described in Patent Document 3 has a central lug groove formed in a zigzag shape so as to fold back within the center region of the tread portion, and one end of either the ground contact front end side or the ground contact rear end side of the central lug groove is located within a block constituting a second block row.

[0004] Japanese Patent No. 5045383 International Publication No. 2022 / 025172 Japanese Patent No. 5276104

[0005] Conventionally, studless tires have emphasized ice performance. To improve ice performance, it is effective to improve the adhesion friction force, so a method of improving the actual contact area by reducing the groove area ratio has been adopted. However, when the groove area ratio is reduced to increase the actual contact area, the amount of snow and water that can enter the grooves during driving on a snow-covered road surface or a wet road surface decreases, so there is a risk that the snow performance and wet performance will easily deteriorate. Therefore, there has been room for improvement in conventional tires considering use on an ice road surface from the perspective of achieving both snow performance and wet performance and ice performance.

[0006] The present invention has been made in view of the above, and aims to provide a tire that can improve ice performance while suppressing a decrease in snow performance and wet performance.

[0007] To solve the above-mentioned problems and achieve the objective, the tire according to the present invention comprises a plurality of circumferential main grooves arranged in the tread portion and extending in the tire circumferential direction, a plurality of widthwise grooves arranged in the tread portion and extending in the tire width direction, and a plurality of land portions partitioned by the circumferential main grooves, wherein the plurality of circumferential main grooves have a shoulder main groove located on the outermost side in the tire width direction and a center main groove adjacent to the shoulder main groove, and the plurality of land portions have a center land portion whose both sides in the tire width direction are partitioned by the center main groove, and a middle land portion whose both sides in the tire width direction are partitioned by the shoulder main groove and the center main groove, wherein the middle land portion has a groove that extends in the tire width direction and whose inner end in the tire width direction is adjacent to the center main groove The present invention relates to a multi-groove system that is repeatedly arranged in the circumferential direction of a tire, each having a first groove which is a widthwise groove whose outer end in the tire width direction terminates within the middle land portion, a second groove which extends in the circumferential direction of the tire and whose end communicates with the first groove, and a third groove which extends in the tire width direction and whose inner end in the tire width direction communicates with the second groove, and whose outer end in the tire width direction communicates with the shoulder main groove. The second groove is characterized in that the end opposite to the end communicating with the first groove communicates with the first groove of an adjacent groove unit in the circumferential direction of the tire, and the center land portion has a multi-groove system that extends in the tire width direction and whose one end communicates with the center main groove and whose other end terminates within the center land portion.

[0008] Furthermore, in the above-described tire, it is preferable that the notch communicates with the center main groove at a position within a range of 20% or less of the pitch length between adjacent first grooves in the tire circumferential direction, relative to the position of the opening of the first groove relative to the center main groove in the tire circumferential direction.

[0009] Furthermore, in the above-mentioned tire, it is preferable that the width Wc of the notch in the tire width direction is within the range of Wb × 0.3 ≤ Wc ≤ Wb × 0.9 with respect to the width Wb of the center land portion in the tire width direction.

[0010] Furthermore, in the above-mentioned tire, it is preferable that the shoulder main groove is formed to extend in the circumferential direction of the tire while swinging in the width direction of the tire.

[0011] Furthermore, in the above-mentioned tire, it is preferable that the second groove has an inclination angle of 3° or more in the tire width direction with respect to the tire circumferential direction.

[0012] Furthermore, in the above-mentioned tire, it is preferable that the second groove has an inclination angle of 30° or less in the tire width direction with respect to the tire circumferential direction.

[0013] Furthermore, in the above-mentioned tire, it is preferable that the groove depth dr1 of the first groove is within the range of D × 0.8 ≤ dr1 ≤ D × 1.0 with respect to the groove depth D of the circumferential main groove.

[0014] Furthermore, in the above-mentioned tire, it is preferable that the groove depth dr3 of the third groove is within the range of D × 0.7 ≤ dr3 ≤ D × 0.9 with respect to the groove depth D of the circumferential main groove.

[0015] Furthermore, in the above-mentioned tire, it is preferable that the groove depth dr2 of the second groove is within the range of D × 0.5 ≤ dr2 ≤ D × 0.7 with respect to the groove depth D of the circumferential main groove.

[0016] Furthermore, in the above-mentioned tire, it is preferable that the center main groove has a groove width within the range of 3.0 mm to 10.0 mm, and the first groove has a groove width within the range of 1.5 mm to 6.0 mm.

[0017] Furthermore, in the above-mentioned tire, it is preferable that the groove width of the second groove is within the range of 1.5 mm to 5.0 mm, and the groove width of the third groove is within the range of 2.0 mm to 7.0 mm.

[0018] Furthermore, in the above-described tire, the middle land portion preferably has a plurality of sipes extending in the tire width direction, and the plurality of sipes have two or more types of sipes with different widths, and include the widest sipe, and the widest sipe is preferably arranged adjacent to the widthwise groove.

[0019] Furthermore, in the above-mentioned tire, it is preferable that the sipe depth ds of the wide sipe is within the range of dr × 0.6 ≤ ds ≤ dr × 0.8 with respect to the groove depth dr of the widthwise groove.

[0020] Furthermore, in the above-mentioned tire, it is preferable that the wide sipe is arranged only on one side in the groove width direction of the adjacent widthwise groove.

[0021] Furthermore, in the above-mentioned tire, it is preferable that the sipe width Wws of the wide sipe is within the range of Ws × 1.3 ≤ Wws ≤ Ws × 3.0 relative to the sipe width ws of the sipes other than the wide sipe.

[0022] Furthermore, in the above-mentioned tire, it is preferable that the tire is a winter tire or an all-season tire in which a plurality of sipes extending in the tire width direction are arranged on the land portion.

[0023] The tire according to the present invention has the effect of improving ice performance while suppressing a decrease in snow performance and wet performance.

[0024] Figure 1 is a meridional cross-sectional view of the tire showing the main part of the pneumatic tire according to the embodiment. Figure 2 is a view taken along the line A-A in Figure 1. Figure 3 is a detailed view of section B in Figure 2. Figure 4 is a detailed view of the groove unit shown in Figure 3. Figure 5 is a cross-sectional view taken along the line C-C in Figure 4. Figure 6 is a cross-sectional view taken along the line E-E in Figure 4. Figure 7 is a cross-sectional view taken along the line F-F in Figure 4. Figure 8 is a cross-sectional view taken along the line G-G in Figure 4. Figure 9 is an explanatory diagram of the notch shown in Figure 4. Figure 10 is a detailed view of section B in Figure 2 and is an explanatory diagram of the middle land portion. Figure 11 is an explanatory diagram showing the state in which the wide sipe is crushed. Figure 12 is an explanatory diagram of a modified example of the pneumatic tire according to the embodiment, showing a form in which the notch intersects the tire equatorial plane. Figure 13A is a chart showing the results of the performance evaluation test of the pneumatic tire. Figure 13B is a chart showing the results of the performance evaluation test of the pneumatic tire.

[0025] [Embodiment] In the following description, a pneumatic tire 1 will be used as an example of a tire according to the present invention. The pneumatic tire 1, which is an example of a tire, can be filled with air, an inert gas such as nitrogen, and other gases.

[0026] Furthermore, in the following explanation, the tire radial direction refers to the direction perpendicular to the tire rotation axis (not shown), which is the rotation axis of the pneumatic tire 1. The inner side of the tire radial direction refers to the side toward the tire rotation axis in the tire radial direction, and the outer side of the tire radial direction refers to the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotation axis as the central axis. The tire width direction refers to the direction parallel to the tire rotation axis. The inner side of the tire width direction refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the outer side of the tire width direction refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane perpendicular to the tire rotation axis and passing through the center of the tire width of the pneumatic tire 1. The position of the tire equatorial plane CL in the tire width direction coincides with the center line in the tire width direction, which is the center position of the pneumatic tire 1 in the tire width direction. The tire width is the distance in the tire width direction between the outermost parts in that direction, that is, the distance between the parts furthest from the tire equatorial plane CL in that direction. The tire equatorial line is a line on the tire equatorial plane CL that runs along the circumferential direction of the pneumatic tire 1. In the following explanation, the tire meridional section refers to the cross-section obtained when the tire is cut by a plane containing the tire's axis of rotation.

[0027] Figure 1 is a meridional cross-sectional view of a pneumatic tire 1 according to this embodiment, showing the main parts of the tire. In this embodiment, the pneumatic tire 1, when viewed in the meridional cross-section of the tire, has a tread portion 2 located at the outermost part in the radial direction of the tire, and the tread portion 2 has a tread rubber 4 made of a rubber composition. The surface of the tread portion 2, that is, the part that comes into contact with the road surface when the vehicle (not shown) equipped with the pneumatic tire 1 is running, is formed as a tread contact surface 3, and the tread contact surface 3 constitutes a part of the contour of the pneumatic tire 1.

[0028] Shoulder portions 5 are located at both outer ends of the tread portion 2 in the tire width direction, and sidewall portions 8 are positioned on the inner side of the shoulder portions 5 in the tire diameter direction. In other words, the sidewall portions 8 are located on both sides of the tread portion 2 in the tire width direction. To put it another way, the sidewall portions 8 are located at two locations on both sides of the pneumatic tire 1 in the tire width direction, forming the outermost exposed portion of the pneumatic tire 1 in the tire width direction.

[0029] A bead portion 10 is located on the radially inner side of each sidewall portion 8, which is located on both sides in the tire width direction. The bead portion 10 is located at two locations on both sides of the tire equatorial plane CL, similar to the sidewall portion 8. That is, a pair of bead portions 10 are located on both sides of the tire equatorial plane CL in the tire width direction. A bead core 11 is provided in each bead portion 10, and a bead filler 12 is provided on the radially outer side of the bead core 11. The bead core 11 is an annular member formed by bundling steel wires called bead wires into a ring shape, and the bead filler 12 is a rubber member located on the radially outer side of the bead core 11.

[0030] Furthermore, a belt layer 14 is arranged in the tread portion 2. The belt layer 14 is composed of a multilayer structure in which a plurality of belts 141, 142 and a belt cover 143 are laminated, and in this embodiment, two layers of belts 141, 142 are laminated. The belts 141, 142 that make up the belt layer 14 are made by coating a plurality of belt cords made of steel or organic fiber material such as polyester, rayon, or nylon with coating rubber and rolling them, and the belt angle, which is defined as the inclination angle of the belt cords with respect to the circumferential direction of the tire, is within a predetermined range (for example, 20° or more and 55° or less). Also, the belt angles of the two layers of belts 141, 142 are different from each other. For this reason, the belt layer 14 is configured as a so-called cross-ply structure in which the two layers of belts 141, 142 are laminated with the inclination directions of the belt cords intersecting each other. In other words, the two layers of belts 141, 142 are provided as so-called cross belts, in which the belt cords of each belt 141, 142 are arranged in a direction that intersects each other.

[0031] Furthermore, the belt cover 143 is constructed by covering multiple belt cover cords made of steel or organic fiber materials such as polyester, rayon, or nylon with coated rubber and then rolling them, so that the belt angle, defined as the inclination angle of the belt cover cords with respect to the circumferential direction of the tire, is within a predetermined range (for example, 0° or more and 10° or less). Also, the belt cover 143 is, for example, a strip material made by covering one or more belt cover cords with coated rubber, and this strip material is constructed by winding it spirally around the tire rotation axis from the outside of the two layers of belts 141 and 142 in the radial direction of the tire.

[0032] A carcass layer 13 containing the cords of radial ply is continuously provided on the inner side of the belt layer 14 in the tire radial direction and on the tire equatorial plane CL side of the sidewall portion 8. Therefore, the pneumatic tire 1 according to this embodiment is configured as a so-called radial tire. The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass ply stacked together, and is toroidally stretched between a pair of bead portions 10 arranged on both sides in the tire width direction to form the tire's skeleton.

[0033] More specifically, the carcass layer 13 is positioned from one of a pair of bead portions 10 located on both sides in the tire width direction to the other bead portion 10, and is wrapped around the bead core 11 in the tire width direction outward along the bead core 11 so as to enclose the bead core 11 and the bead filler 12. The bead filler 12 is a rubber material that is placed in the space formed on the radially outer side of the bead core 11 when the carcass layer 13 is folded back at the bead portion 10. The belt layer 14 is positioned on the radially outer side of the portion of the carcass layer 13 located in the tread portion 2 that spans between the pair of bead portions 10. The carcass ply of the carcass layer 13 is constructed by covering multiple carcass cords made of steel or organic fiber materials such as aramid, nylon, polyester, or rayon with a coating rubber and then rolling them. The carcass cords that make up the carcass ply are arranged in parallel, with an angle in the tire's circumferential direction that aligns with the tire's meridian, while also maintaining an angle in the circumferential direction of the tire.

[0034] In the bead portion 10, rim cushion rubber 17 is arranged on the inner side in the tire radial direction and the outer side in the tire width direction of the bead core 11 and the reversal portion of the carcass layer 13, forming the contact surface of the bead portion 10 with the rim flange. In addition, an inner liner 16 is formed along the carcass layer 13 on the inside of the carcass layer 13, or on the inner side of the carcass layer 13 in the pneumatic tire 1. The inner liner 16 forms the inner surface 18 of the tire, which is the inner surface of the pneumatic tire 1.

[0035] Figure 2 is a view taken along the line A-A in Figure 1. The tread portion 2 has a plurality of circumferential main grooves 30 extending in the tire circumferential direction and a plurality of widthwise grooves 40 extending in the tire width direction arranged on the tread contact surface 3. These circumferential main grooves 30 and widthwise grooves 40 divide the surface of the tread portion 2 into a plurality of land areas 20. In this embodiment, four circumferential main grooves 30 are arranged in the tire width direction. Specifically, the circumferential main grooves 30 consist of two center main grooves 31 arranged on both sides of the tire equatorial plane CL in the tire width direction, and two shoulder main grooves 35, one on each side of the two center main grooves 31 in the tire width direction.

[0036] The circumferential main groove 30 referred to here is a longitudinal groove extending in the circumferential direction of the tire, and has a wear indicator (slip sign) inside that indicates the end of wear. The circumferential main groove 30 formed in this way has a groove width in the range of 3.0 mm to 15.0 mm and a groove depth in the range of 6.0 mm to 10.0 mm.

[0037] The land area 20, which is divided by the circumferential main groove 30, has a center land area 21, a middle land area 22, and a shoulder land area 23. Of these, the center land area 21 is a land area 20 located between two center main grooves 31, and both sides in the tire width direction are divided by the center main groove 31. The middle land area 22 is a land area 20 located between adjacent center main grooves 31 and shoulder main grooves 35 in the tire width direction, and both sides in the tire width direction are divided by the center main groove 31 and the shoulder main groove 35. That is, the middle land area 22 has an inner portion in the tire width direction divided by the center main groove 31, and an outer portion in the tire width direction divided by the shoulder main groove 35. The shoulder land area 23 is a land area 20 located outside the shoulder main groove 35 in the tire width direction, and its inner portion in the tire width direction is divided by the shoulder main groove 35. Furthermore, the middle land section 22 and the shoulder land section 23 are positioned on both sides of the tire equatorial plane CL in the tire width direction, respectively.

[0038] Of the four circumferential main grooves 30, the two shoulder main grooves 35 are both positioned on the outermost side in the tire width direction and extend in the tire circumferential direction. Also, of the four circumferential main grooves 30, the two center main grooves 31 are both positioned adjacent to the shoulder main grooves 35, inside the shoulder main grooves 35 in the tire width direction, and extend in the tire circumferential direction. These shoulder main grooves 35 and center main grooves 31 are formed with a shape that extends in the tire circumferential direction while also oscillating in the tire width direction.

[0039] Figure 3 is a detailed view of section B in Figure 2. The shoulder main groove 35 has a wide section 35a and a narrow section 35b with different groove widths, where the wide section 35a is wider than the narrow section 35b. The wide section 35a and the narrow section 35b of the shoulder main groove 35 are arranged alternately in the tire circumferential direction, and both extend in the tire circumferential direction while being inclined in the tire width direction relative to the tire circumferential direction.

[0040] The edges on both sides of the wide portion 35a in the groove width direction are formed continuously with respect to the edges of the narrow portions 35b located on both sides of the wide portion 35a in the tire circumferential direction. Furthermore, the outer and inner edges of the wide portion 35a in the tire width direction are formed continuously with respect to the edges of the narrow portions 35b on opposite sides of the wide portion 35a in the tire circumferential direction. In other words, the outer edge of the wide portion 35a in the tire width direction is formed continuously with respect to the edge of the narrow portion 35b located on one side in the tire circumferential direction, and the inner edge of the wide portion 35a in the tire width direction is formed continuously with respect to the edge of the narrow portion 35b located on the other side in the tire circumferential direction. As a result, the shoulder main groove 35 is formed to extend in the tire circumferential direction while oscillating in the tire width direction.

[0041] Further, the center main groove 31 has a plurality of inclined portions 31a that extend in the tire circumferential direction and are inclined in the tire width direction with respect to the tire circumferential direction, and the plurality of inclined portions 31a are arranged side by side in the tire circumferential direction. At that time, the inclined portions 31a are connected to each other such that the end portions of adjacent inclined portions 31a in the tire circumferential direction are displaced from each other in the tire width direction. Thereby, the center main groove 31 is formed while extending in the tire circumferential direction and having an amplitude in the tire width direction.

[0042] The center main groove 31 formed in this way has a groove width W within a range of 3.0 mm or more and 10.0 mm or less. That is, the inclined portion 31a of the center main groove 31 has a groove width W within a range of 3.0 mm or more and 10.0 mm or less.

[0043] In the middle land portion 22 partitioned by the shoulder main groove 35 and the center main groove 31, a plurality of groove units 50 having a first groove 51, a second groove 52, and a third groove 53 are arranged, and the plurality of groove units 50 are repeatedly arranged in the tire circumferential direction.

[0044] The first groove 51 included in the groove unit 50 extends in the tire width direction, and the inner end portion in the tire width direction communicates with the center main groove 31, and the outer end portion in the tire width direction terminates within the middle land portion 22. The first groove 51 communicates with the center main groove 31 at a position near the end portion of the inclined portion 31a in the center main groove 31, and extends in the tire width direction while being inclined in the tire circumferential direction with respect to the tire width direction. The first groove 51 extending in the tire width direction is arranged in the middle land portion 22 as the width direction groove 40.

[0045] Further, the second groove 52 extends in the tire circumferential direction, and the end portion in the tire circumferential direction communicates with the first groove 5, and extends in the tire circumferential direction while being inclined in the tire width direction with respect to the tire circumferential direction, and communicates with the first groove 51 near the end portion on the side where the first groove 51 terminates within the middle land portion 22 with respect to the first groove 51 of the same groove unit 50. The inclination direction of the second groove 52 in the tire width direction with respect to the tire circumferential direction is opposite to the inclination direction of the inclined portion 31a of the center main groove 31 in the tire width direction with respect to the tire circumferential direction.

[0046] Further, the third groove 53 is arranged at a position different from that of the first groove 51 in the tire circumferential direction and extends in the tire width direction. The inner end in the tire width direction communicates with the second groove 52, and the outer end in the tire width direction communicates with the shoulder main groove 35. The third groove 53 communicates with the second groove 52 at a position near the center in the length direction of the second groove 52, and communicates with the shoulder main groove 35 at a position near the end of the wide portion 35a of the shoulder main groove 35. The third groove 53 extends in the tire width direction while being inclined in the tire circumferential direction with respect to the tire width direction, and the inclination direction in the tire circumferential direction with respect to the tire width direction is the same as the inclination direction of the first groove 51 in the tire circumferential direction with respect to the tire width direction. The third groove 53 extending in the tire width direction is arranged in the middle land portion 22 as the width direction groove 40.

[0047] The groove unit 50 having the first groove 51, the second groove 52, and the third groove 53 formed as described above has a plurality of groove units 50 repeatedly arranged in the tire circumferential direction in the middle land portion 22. Also, the second groove 52 of each groove unit 50 has an end opposite to the end communicating with the first groove 51 communicating with the first groove 51 of the groove unit 50 adjacent in the tire circumferential direction.

[0048] Specifically, the second groove 52 communicates with the first groove 51 of the groove unit 50 adjacent thereto from the opposite side of the direction in which the second groove 52 of the groove unit 50 extends from the first groove 51, and communicates with the first groove 51 at a position near the center in the length direction of the first groove 51. Thereby, the plurality of groove units 50 arranged in the middle land portion 22 are repeatedly arranged in the tire circumferential direction while communicating with each other.

[0049] The groove unit 50 having the first groove 51, the second groove 52, and the third groove 53 has the groove width W1 of the first groove 51 within the range of 1.5 mm or more and 6.0 mm or less, the groove width W2 of the second groove 52 within the range of 1.5 mm or more and 5.0 mm or less, and the groove width W3 of the third groove 53 within the range of 2.0 mm or more and 7.0 mm or less.

[0050] Figure 4 is a detailed view of the groove unit 50 shown in Figure 3. The first groove 51 has an inclination angle θ1 in the tire circumferential direction relative to the tire width direction that is within the range of 0° to 30°, and the third groove 53 has an inclination angle θ3 in the tire circumferential direction relative to the tire width direction that is within the range of 0° to 30°. The inclination directions of the first groove 51 and the third groove 53 in the tire circumferential direction relative to the tire width direction are the same.

[0051] Furthermore, the inclination angle θ2 of the second groove 52 in the tire width direction with respect to the tire circumferential direction is within the range of 0° to 30°. Preferably, the inclination angle θ2 of the second groove 52 in the tire width direction with respect to the tire circumferential direction is 3° or more. More preferably, the inclination angle θ2 of the second groove 52 in the tire width direction with respect to the tire circumferential direction is within the range of 10° to 20°. The inclination direction of the second groove 52 in the tire width direction with respect to the tire circumferential direction is in the opposite direction to the inclination direction of the inclined portion 31a of the center main groove 31 in the tire width direction with respect to the tire circumferential direction.

[0052] Furthermore, the relative angle θa between the first groove 51 and the second groove 52 is within the range of 70° to 110°, and the relative angle θb between the second groove 52 and the third groove 53 is within the range of 70° to 110°.

[0053] Figure 5 is a cross-sectional view taken along line C-C in Figure 4. Figure 6 is a cross-sectional view taken along line E-E in Figure 4. Figure 7 is a cross-sectional view taken along line F-F in Figure 4. Figure 8 is a cross-sectional view taken along line G-G in Figure 4. Preferably, the groove depth dr1 of the first groove 51 is within the range of D × 0.8 ≤ dr1 ≤ D × 1.0 with respect to the groove depth D of the circumferential main groove 30, and preferably the groove depth dr1 of the first groove 51 is within the range of D × 0.85 ≤ dr1 ≤ D × 0.95 with respect to the groove depth D of the circumferential main groove 30.

[0054] The groove depth dr2 of the second groove 52 is within the range of D × 0.5 ≤ dr2 ≤ D × 0.7 with respect to the groove depth D of the circumferential main groove 30. Preferably, the groove depth dr2 of the second groove 52 is within the range of D × 0.55 ≤ dr2 ≤ D × 0.65 with respect to the groove depth D of the circumferential main groove 30.

[0055] The groove depth dr3 of the third groove 53 is within the range of D × 0.7 ≤ dr3 ≤ D × 0.9 with respect to the groove depth D of the circumferential main groove 30. Preferably, the groove depth dr3 of the third groove 53 is within the range of D × 0.75 ≤ dr3 ≤ D × 0.85 with respect to the groove depth D of the circumferential main groove 30. Furthermore, the relationship between the groove depth dr3 of the third groove 53 and the groove depth dr1 of the first groove 51 satisfies dr1 > dr3.

[0056] Figure 9 is an explanatory diagram of the notch 60 shown in Figure 4. The notch 60 is located in the center land area 21, which is demarcated on both sides in the tire width direction by the center main groove 31. The notch 60 extends in the tire width direction, with one end communicating with the center main groove 31 and the other end terminating within the center land area 21. The width of the notch 60 narrows in the tire circumferential direction from the end communicating with the center main groove 31 towards the end terminating within the center land area 21. In other words, the shape of the notch 60 when viewed in the tire diameter direction, that is, the shape of the notch 60 in plan view, is approximately triangular. In this embodiment, the notch 60 communicates with the center main groove 31 at a position near the end of the inclined portion 31a in the center main groove 31.

[0057] The number of notches 60 located in the center land portion 21 is the same as the number of first grooves 51 that communicate with the center main groove 31 from the outside in the tire width direction. The notches 60 communicate with the center main groove 31 at a position within a range of 20% or less of the pitch length P between adjacent first grooves 51 in the tire circumferential direction, relative to the position of the opening of the first groove 51 relative to the center main groove 31 in the tire circumferential direction. In other words, the distance in the tire circumferential direction between the portion of the notch 60 that communicates with the center main groove 31 and the opening of the first groove 51 relative to the center main groove 31 is within a range of 20% or less of the pitch length P between adjacent first grooves 51 in the tire circumferential direction. Furthermore, it is preferable that the notch 60 communicates with the center main groove 31 at a position within a range of 10% or less of the pitch length P between adjacent first grooves 51 in the tire circumferential direction, relative to the position of the opening of the first groove 51 relative to the center main groove 31 in the tire circumferential direction.

[0058] In this embodiment, the notch 60 is positioned on the extension line of the first groove 51 in the inward direction in the tire width direction. That is, the opening of the notch 60 to the center main groove 31 is positioned opposite to the opening of the first groove 51 to the center main groove 31. Furthermore, the inclination direction of the notch 60 in the tire circumferential direction relative to the tire width direction is the same as that of the first groove 51, and the inclination angle of the notch 60 in the tire width direction is approximately the same as the inclination angle of the first groove 51 in the tire width direction.

[0059] The width Wc of the notch 60 in the tire width direction is within the range of Wb × 0.3 ≤ Wc ≤ Wb × 0.9 relative to the width Wb of the center base 21 in the tire width direction where the notch 60 is located. In this case, the width Wb of the center base 21 in the tire width direction is the maximum width Wb of the center base 21 at the position in the tire circumferential direction where the notch 60 communicates with the center main groove 31. Preferably, the width Wc of the notch 60 in the tire width direction relative to the width Wb of the center base 21 in the tire width direction is within the range of Wb × 0.45 ≤ Wc ≤ Wb × 0.8.

[0060] In this embodiment, the notch 60 does not straddle the tire equatorial plane CL in the tire width direction, and the end of the notch 60 that terminates within the center land portion 21 is located between the center main groove 31 and the tire equatorial plane CL.

[0061] Furthermore, the depth of the notch 60 is the same as the groove depth dr1 of the first groove 51 located in the middle land portion 22. That is, the depth of the notch 60 is within the range of D × 0.8 or more and D × 1.0 or less, relative to the groove depth D of the circumferential main groove 30.

[0062] The notches 60 located in the center land portion 21 include a notch 60 that communicates with one of the two center main grooves 31 that demarcate both sides of the center land portion 21 in the tire width direction, and a notch 60 that communicates with the other center main groove 31. The notches 60 communicating with one of the two center main grooves 31 and the notches 60 communicating with the other center main groove 31 are located at different positions in the tire circumferential direction and are arranged alternately in the tire circumferential direction.

[0063] Furthermore, a middle notch 65 (see Figure 4) is provided in the middle land portion 22. The middle notch 65 is located at the end of the first groove 51 that terminates within the middle land portion 22, and is formed extending outward in the tire width direction from the first groove 51 to terminate within the middle land portion 22. The width of the middle notch 65 in the groove width direction of the first groove 51 is approximately the same as the width of the first groove 51 in the portion communicating with the first groove 51, and the width of the first groove 51 in the groove width direction narrows as it extends outward in the tire width direction from the side where the first groove 51 is located. In other words, the middle notch 65 is formed in a roughly triangular shape in plan view.

[0064] The middle notch 65 is such that the distance Wn from the point where the first groove 51 and the second groove 52 intersect on the extension of the first groove 51 outward in the tire width direction to the shoulder main groove 35 is within the range of Wm × 0.1 ≤ Wn ≤ Wm × 0.8. In this case, the point where the first groove 51 and the second groove 52 intersect is the point where the outer edge of the second groove 52 in the tire width direction intersects with the edge of the first groove 51 on the side where the second groove 52 communicates.

[0065] In this embodiment, the distance Wn from the point where the first groove 51 and the second groove 52 intersect to the end of the middle notch 65 is 50% or less of the distance Wm between the point where the first groove 51 and the second groove 52 intersect on the extension of the first groove 51 and the shoulder main groove 35.

[0066] Thus, the depth of the middle notch 65, which is in communication with the first groove 51 and positioned in the middle land portion 22, is the same as the groove depth dr1 of the first groove 51. That is, the depth of the middle notch 65 is within the range of D × 0.8 or more and D × 1.0 or less, relative to the groove depth D of the circumferential main groove 30.

[0067] Furthermore, shoulder widthwise grooves 45 (see Figure 2) are provided on the shoulder land portion 23. The shoulder widthwise grooves 45 are located on the outside of the shoulder main groove 35 in the tire width direction, and their inner ends in the tire width direction are widthwise grooves 40 that communicate with the shoulder main groove 35. The shoulder widthwise grooves 45 communicate with the shoulder main groove 35 from the outside of the shoulder main groove 35 in the tire width direction at a position near the end of the wide portion 35a of the shoulder main groove 35. The shoulder widthwise grooves 45 communicate with the shoulder main groove 35 at a position different in the tire circumferential direction from the third groove 53, which is located on the middle land portion 22 and communicates with the shoulder main groove 35 from the inside in the tire width direction.

[0068] The outer end of the shoulder widthwise groove 45 in the tire width direction terminates at the so-called design end, which is the end of the tread pattern of the tread portion 2 in the tire width direction. The shoulder widthwise groove 45 formed between the shoulder main groove 35 and the design end is a widthwise groove 40 that defines the shoulder land portion 23 located on the outer side of the shoulder main groove 35 in the tire width direction. As a result, the shoulder land portion 23 is a block-shaped land portion 20, with the inner side in the tire width direction defined by the shoulder main groove 35 and both sides in the tire circumferential direction defined by the shoulder widthwise groove 45.

[0069] Furthermore, the shoulder land portion 23 is provided with shoulder grooves 80 that extend in the circumferential direction of the tire. One end of the shoulder grooves 80 that extend in the circumferential direction of the tire communicates with the shoulder width direction groove 45, and the other end terminates within the shoulder land portion 23. For shoulder grooves 80 provided on the shoulder land portion 23, all shoulder grooves 80 located on the same side in the tire width direction with respect to the tire equatorial plane CL have the same end on the side communicating with the shoulder width direction groove 45 in the circumferential direction of the tire. In other words, all shoulder grooves 80 provided on the shoulder land portion 23, which is partitioned by the same shoulder main groove 35, have the same orientation in the circumferential direction of the tire.

[0070] Furthermore, each of the land sections 20, including the center land section 21, the middle land section 22, and the shoulder land section 23, is provided with a plurality of sipes 70 extending in the tire width direction. The pneumatic tire 1 according to this embodiment, by providing sipes 70 on each land section 20, is applicable to studless tires, which are winter tires that ensure driving performance on icy and snowy roads, or to all-season tires that ensure driving performance in winter.

[0071] The sipes 70 referred to here are formed in the shape of narrow grooves on the tread contact surface 3. When a pneumatic tire 1 is mounted on a specified rim and under specified internal pressure conditions, the walls constituting the narrow grooves do not come into contact with each other when unloaded. However, when a vertical load is applied on a flat plate, and the narrow grooves are located on the contact surface formed on the flat plate, or when the land portion 20 on which the narrow grooves are formed collapses, the walls constituting the narrow grooves, or at least a portion of the parts provided on the walls, come into contact with each other due to the deformation of the land portion 20.

[0072] The term "specified rim" here refers to the "standard rim" specified by JATMA, the "Design Rim" specified by TRA, or the "Measuring Rim" specified by ETRTO. The specified internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "INFLATION PRESSURES" specified by ETRTO.

[0073] Furthermore, the sipe 70 may be a so-called three-dimensional sipe or a two-dimensional sipe. A three-dimensional sipe, as used here, is a sipe 70 having a curved wall surface with amplitude in the width direction of the sipe 70 in both a cross-sectional view with the length direction of the sipe 70 as the normal direction (a cross-sectional view including the width direction and depth direction of the sipe 70) and a cross-sectional view with the depth direction of the sipe 70 as the normal direction (a cross-sectional view including the width direction and depth direction of the sipe 70). A two-dimensional sipe, on the other hand, is a sipe 70 having a straight wall surface in any cross-sectional view with the length direction of the sipe 70 as the normal direction (a cross-sectional view including the width direction and depth direction of the sipe 70).

[0074] It is preferable that the sipes 70 arranged on each land portion 20 are inclined in the same direction as the widthwise grooves 40 which are at the same position in the tire width direction, and in the direction of inclination in the tire circumferential direction with respect to the tire width direction. That is, it is preferable that each sipe 70 is arranged in a direction that extends substantially parallel to the widthwise grooves 40 which are at the same position in the tire width direction.

[0075] For example, a sipe 70 whose position in the tire width direction is the same as that of the first groove 51 preferably has an inclination direction in the tire circumferential direction with respect to the tire width direction that is the same as that of the first groove 51, and a sipe 70 whose position in the tire width direction is the same as that of the third groove 53 preferably has an inclination direction in the tire circumferential direction with respect to the tire width direction that is the same as that of the third groove 53. Similarly, a sipe 70 whose position in the tire width direction is the same as that of the shoulder width direction groove 45 preferably has an inclination direction in the tire circumferential direction with respect to the tire width direction that is the same as that of the shoulder width direction groove 45.

[0076] Of the sipes 70 arranged in each land section 20, the multiple sipes 70 arranged in the middle land section 22 have two or more types of sipes 70 with different widths. Of the multiple sipes 70 arranged in the middle land section 22, the widest sipe 70 is provided as a wide sipe 71 (see Figure 4). The sipes 70 other than the wide sipe 71 arranged in the land section 20 are arranged in a zigzag shape, for example, by extending in the tire width direction and repeatedly bending and oscillating in the tire circumferential direction. The ends of each sipe 70 other than the wide sipe 71 may terminate within the land section 20, or they may communicate with other grooves.

[0077] The wide sipes 71 located in the middle land section 22 are positioned adjacent to the first groove 51 and the third groove, which are widthwise grooves 40 located in the middle land section 22. The wide sipes 71 are positioned only on one side in the groove width direction of the first groove 51 or the third groove to which the wide sipes 71 are adjacent. For example, the wide sipe 71 adjacent to the first groove 51 is positioned near the first groove 51 on the side where the second groove 52, which communicates with the end of the first groove 51, is located. Similarly, the wide sipe 71 adjacent to the third groove 53 is positioned in the tire circumferential direction relative to the third groove 53 on the opposite side from the wide sipe 71 adjacent to the first groove 51 in the tire circumferential direction relative to the first groove 51.

[0078] Of the wide sipes 71 arranged in the middle land section 22, the wide sipes 71 adjacent to the first groove 51 are formed substantially parallel to the first groove 51, and the wide sipes 71 adjacent to the third groove 53 are formed substantially parallel to the third groove 53. Furthermore, the inner end of the wide sipe 71 adjacent to the first groove 51 communicates with the center main groove 31 in the tire width direction, and the outer end in the tire width direction terminates within the middle land section 22, and its length is shorter than that of the first groove 51. Similarly, the outer end of the wide sipe 71 adjacent to the third groove 53 communicates with the shoulder main groove 35 in the tire width direction, and the inner end in the tire width direction terminates within the middle land section 22, and its length is shorter than that of the third groove 53.

[0079] The wide sipes 71, which are positioned adjacent to the first groove 51 and the third groove 53, are formed to extend in a straight line when viewed from above. The sipe width Wws of the wide sipes 71 is within the range of Ws × 1.3 ≤ Wws ≤ Ws × 3.0 relative to the sipe width ws of the sipes 70 other than the wide sipes 71. Specifically, the sipe width ws of the sipes 70 other than the wide sipes 71 is 1.0 mm or less, and the sipe width Wws of the wide sipes 71 is within the range of 0.5 mm to 1.5 mm. In addition, the depth of each sipe 70 is within the range of 2.0 mm to 10.0 mm in maximum depth from the tread contact surface 3.

[0080] Furthermore, the sipe depth ds (see Figures 6 and 8) of the wide sipe 71 is within the range of dr × 0.6 ≤ ds ≤ dr × 0.8 relative to the groove depth dr of the widthwise groove 40. In other words, the sipe depth ds of the wide sipe 71 adjacent to the first groove 51 is within the range of dr1 × 0.6 ≤ ds ≤ dr1 × 0.8 relative to the groove depth dr1 of the first groove 51, and the sipe depth ds of the wide sipe 71 adjacent to the third groove 53 is within the range of dr3 × 0.6 ≤ ds ≤ dr3 × 0.8 relative to the groove depth dr3 of the third groove 53.

[0081] Furthermore, the distance B1 between the wide sipe 71 adjacent to the first groove 51 and the first groove 51 is within the range of W1 × 0.7 ≤ B1 ≤ W1 × 1.2 with respect to the groove width W1 of the first groove 51. Similarly, the distance B3 between the wide sipe 71 adjacent to the third groove 53 and the third groove 53 is within the range of W3 × 0.8 ≤ B3 ≤ W3 × 1.6 with respect to the groove width W3 of the third groove 53.

[0082] Figure 10 is a detailed view of section B in Figure 2 and is an explanatory diagram of the middle land section 22. The middle land section 22 has a first block section 22a and a second block section 22b, as multiple groove units 50 having a first groove 51, a second groove 52, and a third groove 53 are repeatedly arranged in the circumferential direction of the tire.

[0083] The first block section 22a is a block-shaped portion in the middle land section 22 where the inner portion in the tire width direction is demarcated by the center main groove 31, the outer portion in the tire width direction is demarcated by the second groove 52, and both sides in the tire circumferential direction are demarcated by the first groove 51. The second block section 22b is a block-shaped portion in the middle land section 22 where the inner portion in the tire width direction is demarcated by the second groove 52 and the first groove 51, the outer portion in the tire width direction is demarcated by the shoulder main groove 35, and both sides in the tire circumferential direction are demarcated by the third groove 53.

[0084] In the middle track section 22, the first block section 22a and the second block section 22b are partitioned in this manner, and the area of ​​the tread contact surface 3 of the first block section 22a and the area of ​​the tread contact surface 3 of the second block section 22b are approximately the same size. In this embodiment, the middle track section 22 satisfies the relationship A2 × 0.9 ≤ A1 ≤ A2 × 1.1 between the area A1 of the tread contact surface 3 of the first block section 22a and the area A2 of the tread contact surface 3 of the second block section 22b.

[0085] Furthermore, the second groove 52 that defines the outer portion of the first block portion 22a in the tire width direction communicates with one of the two first grooves 51 that define the end of the first block portion 22a in the tire circumferential direction, near the end of the first groove 51, and communicates with the other first groove 51 near the center of the first groove 51.

[0086] Therefore, the first block portion 22a is formed in a substantially trapezoidal shape, such that the edge length is longer in the portion of the first groove 51 on the side where the second groove 52 communicates with the end than in the portion of the first groove 51 on the side where the second groove 52 communicates with the center. In the first block portion 22a formed in this substantially trapezoidal shape, the relationship between the length La of the short edge portion 22aa, which is the shorter edge portion of the first block portion 22a, and the length Lb of the long edge portion 22ab, which is the longer edge portion, is within the range of Lb × 0.4 ≤ La ≤ Lb × 0.6.

[0087] When mounting the pneumatic tire 1 according to this embodiment onto a vehicle, the pneumatic tire 1 is mounted onto a rim wheel, and then inflated by filling it with air before mounting it to the vehicle. When a vehicle equipped with the pneumatic tire 1 is driven, the pneumatic tire 1 rotates while the lower part of the tread contact surface 3 of the tread portion 2 contacts the road surface. When a vehicle equipped with the pneumatic tire 1 is driven on a dry road surface, it mainly operates by transmitting driving force and braking force to the road surface and generating turning force through the frictional force between the tread contact surface 3 and the road surface.

[0088] Furthermore, when driving on a wet road surface, water between the tread contact surface 3 and the road surface enters grooves such as the circumferential main grooves 30 and the widthwise grooves 40, as well as sipes 70, and these grooves drain the water between the tread contact surface 3 and the road surface as the vehicle drives. As a result, the tread contact surface 3 makes contact with the road surface more easily, and the frictional force between the tread contact surface 3 and the road surface allows the vehicle to drive.

[0089] Furthermore, when driving on a snowy road surface, the pneumatic tire 1 compacts the snow on the road surface with its tread contact surface 3, and the snow on the road surface enters the circumferential main grooves 30 and the widthwise grooves 40, compacting these snow within the grooves as well. In this state, when driving force or braking force is applied to the pneumatic tire 1, or when a force is applied in the tire width direction due to the vehicle turning, a shear force, known as a snow column shear force, is generated between the pneumatic tire 1 and the snow. When driving on a snowy road surface, this snow column shear force creates resistance between the pneumatic tire 1 and the road surface, allowing driving force and braking force to be transmitted to the road surface and ensuring snow traction. As a result, the vehicle can drive on snowy road surfaces.

[0090] Furthermore, when driving on snowy or icy surfaces, the edge effect of the circumferential main grooves 30, the lateral grooves 40, and the sipes 70 is also utilized. In other words, when driving on snowy or icy surfaces, the resistance created by the edges of the circumferential main grooves 30, the lateral grooves 40, and the sipes 70 catching on the snow or ice surface is also utilized. Additionally, when driving on icy surfaces, the sipes 70 absorb water from the surface of the icy surface, removing the water film between the icy surface and the tread contact surface 3, thereby making it easier for the icy surface and the tread contact surface 3 to make contact. As a result, the tread contact surface 3 experiences increased resistance with the icy surface due to adhesive friction and the edge effect, ensuring the driving performance of the vehicle equipped with the pneumatic tire 1.

[0091] In recent years, with studless tires and all-season tires designed to ensure winter driving performance, ice performance—the driving performance on icy roads—has become a crucial factor. Improving adhesive friction is effective in enhancing ice performance, and one possible method is to increase the actual contact area by reducing the groove area ratio. However, if the groove area ratio is reduced to increase the actual contact area, the amount of snow or water that can enter the grooves when driving on snowy or wet roads decreases. In this case, there is a risk that snow performance (driving performance on snowy roads) and wet performance (driving performance on wet roads) will deteriorate.

[0092] In contrast, in the pneumatic tire 1 according to this embodiment, a plurality of groove units 50 are repeatedly arranged in the circumferential direction of the tire in the middle land portion 22, each having a first groove 51 extending in the tire width direction and communicating with the center main groove 31, a second groove 52 extending in the tire circumferential direction and having its end communicating with the first groove 51, and a third groove 53 extending in the tire width direction and communicating with the shoulder main groove 35. Therefore, the first groove 51 and the third groove 53 extending in the tire width direction can secure an edge component in the tire circumferential direction, and the second groove 52 extending in the tire circumferential direction can also secure an edge component in the tire width direction. As a result, both the edge effect during driving and braking, and the edge effect during turning can be improved, thereby enhancing ice and snow performance.

[0093] Furthermore, since the first groove 51 communicates with the center main groove 31 and the third groove 53 communicates with the shoulder main groove 35, the first groove 51 and the third groove 53 are positioned in different ranges in the tire width direction. This suppresses the reduction in rigidity of the middle land portion 22 when the edge component in the tire circumferential direction is secured by the first groove 51 and the third groove 53. As a result, it is possible to suppress the middle land portion 22 from deforming significantly due to the load during driving on icy roads, and the contact pressure of the middle land portion 22 can be secured, thereby improving ice performance.

[0094] Furthermore, since the first groove 51 communicates with the center main groove 31 and the third groove 53 communicates with the shoulder main groove 35, water that enters the first groove 51 when driving on a wet road surface can be directed to the center main groove 31, and water that enters the third groove 53 can be directed to the shoulder main groove 35. In addition, since the second groove 52 communicates with both the first groove 51 and the third groove 53, water that enters the second groove 52 when driving on a wet road surface can be directed to the center main groove 31 via the first groove 51 or to the shoulder main groove 35 via the third groove 53. As a result, water on the road surface can be efficiently drained when driving on a wet road surface, making it easier for the tread contact surface 3 to make contact, and thus improving wet performance.

[0095] Furthermore, the center base 21 has multiple notches 60 that extend in the tire width direction, with one end communicating with the center main groove 31 and the other end terminating within the center base 21. Therefore, the notches 60 increase the amount of edge, improving ice and snow performance. Also, because the notches 60 increase the amount of edge in the center base 21, a decrease in the rigidity of the center base 21 is suppressed, ensuring sufficient ground pressure on the center base 21, thus improving ice performance. As a result, ice performance can be improved while minimizing a decrease in snow and wet performance.

[0096] Furthermore, the notch 60 communicates with the center main groove 31 at a position within 20% or less of the pitch length of the first groove 51, relative to the position of the opening of the first groove 51 relative to the center main groove 31 in the tire circumferential direction. This allows the first groove 51 and the notch 60 to communicate with the center main groove 31 at a close position in the tire circumferential direction. As a result, the opening area of ​​the center main groove 31 relative to the tread contact surface 3 near the portion of the center main groove 31 where the first groove 51 and the notch 60 communicate can be increased. Consequently, when driving on a snowy road surface, a large amount of snow can enter the portion of the center main groove 31 where the first groove 51 and the notch 60 communicate, and the snow column shear force can be increased by the large amount of snow that has entered the center main groove 31. As a result, snow performance can be improved.

[0097] Furthermore, since the width Wc of the notch 60 in the tire width direction is within the range of Wb × 0.3 ≤ Wc ≤ Wb × 0.9 relative to the width Wb of the center base 21 in the tire width direction, snow performance and ice performance can be improved. In other words, if the width Wc of the notch 60 is Wc < Wb × 0.3 relative to the width Wb of the center base 21, the width Wc of the notch 60 is too small, and there is a risk that even if the notch 60 is placed on the center base 21, it will be difficult to increase the amount of edge. In this case, even if the notch 60 is placed on the center base 21, there is a risk that it will be difficult to effectively improve ice performance and snow performance. Also, if the width Wc of the notch 60 is Wc > Wb × 0.9 relative to the width Wb of the center base 21, the width Wc of the notch 60 is too large, and there is a risk that the rigidity of the center base 21 will be easily reduced by the notch 60. In this case, the reduced rigidity of the center land portion 21 may make it difficult to secure ground pressure on the center land portion 21, potentially making it difficult to improve ice performance.

[0098] In contrast, if the width Wc of the notch 60 is within the range of Wb × 0.3 ≤ Wc ≤ Wb × 0.9 relative to the width Wb of the center land portion 21, the amount of edge can be increased while suppressing a decrease in the rigidity of the center land portion 21. As a result, snow performance and ice performance can be improved more reliably.

[0099] Furthermore, since the shoulder main groove 35 is formed extending in the circumferential direction of the tire while oscillating in the width direction of the tire, the amount of edge of the shoulder main groove 35 can be increased, and the shear force of the snow column due to the snow that enters the shoulder main groove 35 can be increased. As a result, snow performance and ice performance can be improved more reliably.

[0100] Furthermore, since the second groove 52 has an inclination angle θ2 in the tire width direction relative to the tire circumferential direction of 3° or more, it can more reliably improve snow and ice performance. In other words, if the inclination angle θ2 of the second groove 52 is less than 3°, the inclination angle θ2 of the second groove 52 is too small, which may make it difficult to secure the edge component of the second groove 52 in the tire circumferential direction. In this case, it may be difficult to enhance the edge effect of the second groove 52 when driving or braking on icy or snowy roads.

[0101] In contrast, when the inclination angle θ2 of the second groove 52 is 3° or more, it becomes easier to secure the edge component of the second groove 52 in the circumferential direction of the tire, thereby enhancing the edge effect of the second groove 52 during driving and braking on icy and snowy roads. As a result, snow performance and ice performance can be improved more reliably.

[0102] Furthermore, since the inclination angle θ2 of the second groove 52 in the tire width direction relative to the tire circumferential direction is 30° or less, ice performance can be improved more reliably. In other words, if the inclination angle θ2 of the second groove 52 is greater than 30°, there is a risk that there will be parts where the distance between the second groove 52 and the center main groove 31 or shoulder main groove 35 becomes too small. In this case, the middle land section 22 where the second groove 52 is located may have excessively low rigidity in some areas, which may make it difficult to improve ice performance as the contact pressure when driving on an icy road surface tends to decrease.

[0103] In contrast, if the inclination angle θ2 of the second groove 52 is 30° or less, it is possible to suppress the occurrence of areas where the distance between the second groove 52 and the center main groove 31 or shoulder main groove 35 becomes too small. This prevents the rigidity of the middle land section 22 from becoming too low in certain areas, and ensures sufficient ground pressure when the middle land section 22 makes contact with the ground. As a result, ice performance can be improved more reliably.

[0104] Furthermore, since the groove depth dr1 of the first groove 51 is within the range of D × 0.8 ≤ dr1 ≤ D × 1.0 relative to the groove depth D of the circumferential main groove 30, it is possible to improve ice performance while more reliably suppressing the decrease in wet performance. In other words, if the groove depth dr1 of the first groove 51 is dr1 < D × 0.8 relative to the groove depth D of the circumferential main groove 30, the groove depth dr1 of the first groove 51 is too shallow, which may reduce the amount of water that enters the first groove 51 when driving on a wet road surface. In this case, it becomes difficult to ensure drainage by the first groove 51, which may make it difficult to improve wet performance. Also, if the groove depth dr1 of the first groove 51 is dr1 > D × 1.0 relative to the groove depth D of the circumferential main groove 30, the groove depth dr1 of the first groove 51 is too deep, which may easily reduce the rigidity of the middle land section 22 where the first groove 51 is located. In this case, the middle ground section 22 is more susceptible to deformation due to the load at ground contact, which may lead to a decrease in ground pressure when driving on an icy surface, making it difficult to improve performance on ice.

[0105] In contrast, if the groove depth dr1 of the first groove 51 is within the range of D × 0.8 ≤ dr1 ≤ D × 1.0 relative to the groove depth D of the circumferential main groove 30, then the rigidity of the middle land portion 22 can be ensured, and the ground pressure when the middle land portion 22 makes contact with the ground can be ensured, while at the same time, when driving on a wet road surface, water on the road surface can be more reliably drawn into the first groove 51 to ensure drainage. As a result, the deterioration of wet performance can be more reliably suppressed while improving ice performance.

[0106] Furthermore, since the groove depth dr3 of the third groove 53 is within the range of D × 0.7 ≤ dr3 ≤ D × 0.9 relative to the groove depth D of the circumferential main groove 30, it is possible to improve ice performance while more reliably suppressing the deterioration of wet performance and snow performance. In other words, if the groove depth dr3 of the third groove 53 is dr3 < D × 0.7 relative to the groove depth D of the circumferential main groove 30, the groove depth dr3 of the third groove 53 is too shallow, which may result in less water entering the third groove 53 when driving on a wet road surface, or less snow entering the third groove 53 when driving on a snowy road surface. In this case, it may become difficult to ensure drainage by the third groove 53, making it difficult to improve wet performance, or it may become difficult to generate snow column shear force in the third groove 53, making it difficult to improve snow performance. Furthermore, if the groove depth dr3 of the third groove 53 is dr3 > D × 0.9 with respect to the groove depth D of the circumferential main groove 30, the groove depth dr3 of the third groove 53 is too deep, which may easily reduce the rigidity of the middle land section 22 where the third groove 53 is located. In this case, the middle land section 22 is more susceptible to deformation due to the load at ground contact, which may easily reduce the ground pressure when driving on an icy road surface, making it difficult to improve ice performance.

[0107] In contrast, if the groove depth dr3 of the third groove 53 is within the range of D × 0.7 ≤ dr3 ≤ D × 0.9 relative to the groove depth D of the circumferential main groove 30, it is possible to ensure the rigidity of the middle land portion 22 and the ground pressure when the middle land portion 22 makes contact with the ground, while also ensuring drainage by more reliably allowing water on the road surface to enter the third groove 53 when driving on a wet road surface, and making it easier to generate snow column shear force in the third groove 53 more reliably when driving on a snowy road surface. As a result, it is possible to improve ice performance while more reliably suppressing the deterioration of wet performance and snow performance.

[0108] Furthermore, since the groove depth dr2 of the second groove 52 is within the range of D × 0.5 ≤ dr2 ≤ D × 0.7 relative to the groove depth D of the circumferential main groove 30, it is possible to improve ice performance while more reliably suppressing the decrease in wet performance. In other words, if the groove depth dr2 of the second groove 52 is dr2 < D × 0.5 relative to the groove depth D of the circumferential main groove 30, the groove depth dr2 of the second groove 52 is too shallow, which may reduce the amount of water that enters the second groove 52 when driving on a wet road surface. In this case, it becomes difficult to ensure drainage by the second groove 52, which may make it difficult to improve wet performance. Also, if the groove depth dr2 of the second groove 52 is dr2 > D × 0.7 relative to the groove depth D of the circumferential main groove 30, the groove depth dr2 of the second groove 52 is too deep, which may easily reduce the rigidity of the middle land section 22 where the second groove 52 is located. In this case, the middle ground section 22 is more susceptible to deformation due to the load at ground contact, which may lead to a decrease in ground pressure when driving on an icy surface, making it difficult to improve performance on ice.

[0109] In contrast, if the groove depth dr2 of the second groove 52 is within the range of D × 0.5 ≤ dr2 ≤ D × 0.7 relative to the groove depth D of the circumferential main groove 30, the rigidity of the middle land portion 22 is ensured, and the ground pressure when the middle land portion 22 makes contact with the ground is secured, while at the same time, when driving on a wet road surface, water on the road surface can be more reliably drawn into the second groove 52 to ensure drainage. As a result, the deterioration of wet performance can be more reliably suppressed while improving ice performance.

[0110] Furthermore, since the groove width W of the center main groove 31 is within the range of 3.0 mm to 10.0 mm, and the groove width W1 of the first groove 51 is within the range of 1.5 mm to 6.0 mm, it is possible to improve ice performance while more reliably suppressing the deterioration of wet performance. In other words, if the groove width W of the center main groove 31 is less than 3.0 mm, or the groove width W1 of the first groove 51 is less than 1.5 mm, the groove width W of the center main groove 31 and the groove width W1 of the first groove 51 are too narrow, which may reduce the amount of water that enters the center main groove 31 and the first groove 51 when driving on a wet road surface. In this case, it becomes difficult to ensure drainage by the center main groove 31 and the first groove 51, which may make it difficult to improve wet performance. Furthermore, if the groove width W of the center main groove 31 is greater than 10.0 mm, or if the groove width W1 of the first groove 51 is greater than 6.0 mm, the groove width W of the center main groove 31 and the groove width W1 of the first groove 51 are too wide, which may easily reduce the rigidity of the center land area 21 and the middle land area 22 partitioned by the center main groove 31, as well as the rigidity of the middle land area 22 where the first groove 51 is located. In this case, the center land area 21 and the middle land area 22 are more susceptible to deformation due to the load when in contact with the ground, which may easily reduce the ground pressure when driving on an icy road surface, making it difficult to improve performance on ice.

[0111] In contrast, if the groove width W of the center main groove 31 is within the range of 3.0 mm to 10.0 mm, and the groove width W1 of the first groove 51 is within the range of 1.5 mm to 6.0 mm, the rigidity of the center land portion 21 and the middle land portion 22 can be ensured, and while ensuring the ground pressure when these land portions 20 make contact with the ground, when driving on a wet road surface, water on the road surface can be more reliably drawn into the center main groove 31 and the first groove 51 to ensure drainage. As a result, the deterioration of wet performance can be more reliably suppressed while improving ice performance.

[0112] Furthermore, since the groove width W2 of the second groove 52 is within the range of 1.5 mm to 5.0 mm, and the groove width W3 of the third groove 53 is within the range of 2.0 mm to 7.0 mm, it is possible to improve ice performance while more reliably suppressing the deterioration of wet performance. In other words, if the groove width W2 of the second groove 52 is less than 1.5 mm, or the groove width W3 of the third groove 53 is less than 2.0 mm, the groove width W2 of the second groove 52 and the groove width W3 of the third groove 53 are too narrow, which may reduce the amount of water that enters the second groove 52 and the third groove 53 when driving on a wet road surface. In this case, it becomes difficult to ensure drainage by the second groove 52 and the third groove 53, which may make it difficult to improve wet performance. Furthermore, if the groove width W2 of the second groove 52 is greater than 5.0 mm, or the groove width W3 of the third groove 53 is greater than 7.0 mm, the groove width W2 of the second groove 52 and the groove width W3 of the third groove 53 are too wide, which may easily reduce the rigidity of the middle land section 22 where the second groove 52 and the third groove 53 are located. In this case, the middle land section 22 is more susceptible to deformation due to the load at ground contact, which may easily reduce the ground pressure when driving on an icy road surface, making it difficult to improve ice performance.

[0113] In contrast, if the groove width W2 of the second groove 52 is within the range of 1.5 mm to 5.0 mm, and the groove width W3 of the third groove 53 is within the range of 2.0 mm to 7.0 mm, then the rigidity of the middle land section 22 is ensured, and the ground pressure when the middle land section 22 makes contact with the ground is secured, while at the same time, when driving on a wet road surface, water on the road surface can be more reliably drawn into the second groove 52 and the third groove 53 to ensure drainage. As a result, the deterioration of wet performance can be more reliably suppressed while improving ice performance.

[0114] Furthermore, since wide sipes 71 are placed adjacent to the first groove 51 and third groove 53, which are widthwise grooves 40 located in the middle land section 22, it is possible to suppress the crushing of the first groove 51 and third groove 53 during braking and driving. In other words, when the part of the middle land section 22 where the widthwise grooves 40, the first groove 51 and third groove 53, are located makes contact with the ground, the middle land section 22 deforms due to the load at the time of contact. If the middle land section 22 deforms without the wide sipes 71, the first groove 51 and third groove 53 will deform in a direction that narrows the groove width due to the deformation of the middle land section 22, and it is conceivable that the opposing groove walls will come into contact with each other and the grooves will close. In this case, it will be difficult for water or snow to enter the first groove 51 and third groove 53 when driving on wet roads or snowy roads, which may make it difficult to improve wet performance and snow performance.

[0115] Figure 11 is an explanatory diagram showing a state in which the wide sipe 71 is crushed. In contrast, in this embodiment, the wide sipe 71 is positioned adjacent to the first groove 51 and the third groove 53, which are widthwise grooves 40, on the middle land section 22. Therefore, when the middle land section 22 deforms due to the portion of the middle land section 22 where the first groove 51 and the third groove 53 are located making contact with the ground, the wide sipe 71 deforms and closes in the sipe width direction, as shown in Figure 11, thereby absorbing the deformation of the middle land section 22 when it makes contact with the ground. As a result, even when the middle land section 22 deforms due to the load when it makes contact with the ground, the crushing of the first groove 51 and the third groove 53, which are widthwise grooves 40, can be suppressed. Consequently, when driving on wet roads or snowy roads, water and snow on the road surface can be more reliably allowed to enter the first groove 51 and the third groove 53. As a result, wet performance and snow performance can be more reliably improved.

[0116] Furthermore, since the sipe depth ds of the wide sipe 71 is within the range of dr × 0.6 ≤ ds ≤ dr × 0.8 relative to the groove depth dr of the widthwise groove 40, it is possible to improve ice performance while more reliably suppressing the deterioration of snow performance and wet performance. In other words, if the sipe depth ds of the wide sipe 71 is ds < dr × 0.6 relative to the groove depth dr of the adjacent widthwise groove 40, the sipe depth ds is too shallow, and even if the wide sipe 71 is placed adjacent to the widthwise groove 40, it may be difficult to suppress the collapse of the widthwise groove 40, that is, the collapse of the first groove 51 and the third groove 53, when the middle land section 22 makes contact with the ground. In this case, when driving on a wet road surface or a snowy road surface, it may be difficult for water or snow on the road surface to enter the first groove 51 and the third groove 53, and it may be difficult to improve wet performance and snow performance. Furthermore, if the sipe depth ds of the wide sipe 71 is ds > dr × 0.8 with respect to the groove depth dr of the adjacent widthwise groove 40, the sipe depth ds is too deep, which may easily reduce the rigidity of the middle land section 22 where the wide sipe 71 is located. In this case, the middle land section 22 is more susceptible to deformation due to the load at ground contact, which may easily reduce the ground pressure when driving on an icy road surface, making it difficult to improve ice performance.

[0117] In contrast, if the sipe depth ds of the wide sipe 71 is within the range of dr × 0.6 ≤ ds ≤ dr × 0.8 with respect to the groove depth dr of the adjacent widthwise groove 40, the deformation of the middle land section 22 when it makes contact with the ground can be absorbed by the wide sipe 71 while suppressing a decrease in the rigidity of the middle land section 22. As a result, the ground pressure when the middle land section 22 makes contact with the ground can be secured while the wide sipe 71 can suppress the collapse of the first groove 51 and the third groove 53, which are widthwise grooves 40, when the middle land section 22 makes contact with the ground. As a result, the ice performance can be improved while more reliably suppressing a decrease in snow performance and wet performance.

[0118] Furthermore, since the wide sipes 71 are positioned only on one side in the groove width direction of the adjacent widthwise grooves 40, it is possible to prevent the rigidity of the middle land section 22 where the wide sipes 71 are positioned from becoming too low. This suppresses deformation of the middle land section 22 when driving on an icy road surface and ensures sufficient ground pressure on the middle land section 22. As a result, ice performance can be improved more reliably.

[0119] Furthermore, the wide sipe 71 has a sipe width Wws that is within the range of Ws × 1.3 ≤ Wws ≤ Ws × 3.0 compared to the sipe width ws of the other sipes 70. This allows for a more reliable reduction in the decrease of snow and wet performance while improving ice performance. In other words, if the sipe width Wws of the wide sipe 71 is Wws < Ws × 1.3 compared to the sipe width ws of the other sipes 70, the sipe width Wws of the wide sipe 71 is too narrow, and there is a risk that the wide sipe 71 will collapse prematurely when the middle land section 22 makes contact with the ground. In this case, the deformation of the middle section 22 when it makes contact with the ground becomes difficult to absorb by the wide sipe 71. Therefore, even if the wide sipe 71 is placed adjacent to the widthwise groove 40, it may become difficult to suppress the collapse of the widthwise groove 40 when the middle section 22 makes contact with the ground, i.e., the collapse of the first groove 51 and the third groove 53. Also, if the sipe width Wws of the wide sipe 71 is Wws > Ws × 3.0 compared to the sipe width ws of the other sipes 70, the sipe width Wws of the wide sipe 71 is too wide, which may easily reduce the rigidity of the middle section 22 where the wide sipe 71 is placed. In this case, the middle section 22 becomes more susceptible to deformation due to the load when it makes contact with the ground, which may easily reduce the ground pressure when driving on an icy surface, making it difficult to improve performance on ice.

[0120] In contrast, if the sipe width Wws of the wide sipe 71 is within the range of Ws × 1.3 ≤ Wws ≤ Ws × 3.0 relative to the sipe width ws of the sipes 70 other than the wide sipe 71, then the deformation of the middle land section 22 when it makes contact with the ground can be absorbed by the wide sipe 71 while suppressing the decrease in rigidity of the middle land section 22. As a result, the ground pressure when the middle land section 22 makes contact with the ground can be secured while the first groove 51 and the third groove 53, which are widthwise grooves 40, can be suppressed by the wide sipe 71 when the middle land section 22 makes contact with the ground. As a result, the decrease in snow performance and wet performance can be suppressed more reliably while improving ice performance.

[0121] Furthermore, since multiple sipes 70 extending in the tire width direction are arranged on the land portion 20, the amount of edge can be increased by the multiple sipes 70, and the increased edge effect can improve driving performance on snowy and icy surfaces. As a result, it is possible to improve ice performance while more reliably suppressing the deterioration of snow performance.

[0122] [Modification] In the above-described embodiment, the notch 60 located in the center land portion 21 does not intersect the tire equatorial plane CL, but the notch 60 may be formed to straddle the tire equatorial plane CL in the tire width direction.

[0123] Figure 12 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the embodiment, in which the notch 60 intersects the tire equatorial plane CL. The notch 60, which is located in the center land portion 21, is formed to straddle the tire equatorial plane CL in the tire width direction, as shown in Figure 12, for example, and the end that terminates within the center land portion 21 may be located near a different center main groove 31 from the center main groove 31 through which the notch 60 communicates.

[0124] Furthermore, in the embodiment described above, the notch 60 is positioned on the extension of the first groove 51, but the notch 60 may be positioned at a location other than the extension of the first groove 51. For example, as shown in Figure 12, the opening of the notch 60 to the center main groove 31 may be offset in the tire circumferential direction from the opening of the first groove 51 to the center main groove 31. The notch 60 only needs to communicate with the center main groove 31 at a position within 20% or less of the pitch length P (see Figure 9) between adjacent first grooves 51 in the tire circumferential direction, relative to the position of the opening of the first groove 51 to the center main groove 31 in the tire circumferential direction.

[0125] Furthermore, in the above-described embodiment, the distance Wn from the point where the first groove 51 and the second groove 52 intersect to the end of the middle notch 65 is 50% or less of the distance Wm between the point where the first groove 51 and the second groove 52 intersect on the extension of the first groove 51 and the shoulder main groove 35. However, the distance Wn may be greater than 50% of the distance Wm. That is, the outer end of the middle notch 65 in the tire width direction may be located near the shoulder main groove 35, as shown in Figure 12.

[0126] Furthermore, in the above-described embodiment, the center main groove 31 and the shoulder main groove 35 are formed in a zigzag shape by extending in the circumferential direction of the tire and oscillating in the width direction of the tire. However, the center main groove 31 and the shoulder main groove 35 may be formed in a shape other than a zigzag shape. That is, the center main groove 31 and the shoulder main groove 35 may extend in a straight line in the circumferential direction of the tire.

[0127] Furthermore, the embodiments and modifications described above may be combined as appropriate. In addition, although the embodiments described above used pneumatic tire 1 as an example of a tire according to the present invention, the tire according to the present invention may be other than pneumatic tire 1. The tire according to the present invention may be, for example, a so-called airless tire that can be used without filling with gas.

[0128] [Examples] Figures 13A and 13B are charts showing the results of performance evaluation tests of pneumatic tires. Below, we will describe the performance evaluation tests conducted on the above-mentioned pneumatic tire 1, comparing it to a conventional pneumatic tire and the pneumatic tire 1 according to the present invention. The performance evaluation tests included tests for snow performance, wet performance, and ice performance.

[0129] The performance evaluation test was conducted by mounting a pneumatic tire (195 / 65R15 91Q size, as defined by JATMA) onto a JATMA standard rim wheel with a rim size of 15 x 6.5J, and then mounting the test tire on a front-wheel-drive evaluation vehicle with an engine displacement of 1800cc, adjusting the air pressure to 240kPa, and driving the evaluation vehicle.

[0130] The evaluation method for each test item was as follows: For snow performance, a braking test was conducted on a test course with a snow-covered road surface using an evaluation vehicle equipped with the test tires. The reciprocal of the braking distance was expressed as an index with the conventional example described later set to 100. A higher index indicates shorter braking distance on snow-covered roads and superior snow performance.

[0131] Furthermore, wet performance was evaluated by conducting braking tests on an asphalt road test course with the test tires fitted to an evaluation vehicle, where the tires were sprayed with water to a depth of 1.0 mm. The reciprocal of the braking distance was expressed as an index with the conventional example described later set to 100. A higher index indicates a shorter braking distance on a wet road surface and superior wet performance.

[0132] Furthermore, ice performance was evaluated by conducting braking tests on an icy test course using evaluation vehicles equipped with test tires, and expressing the reciprocal of the braking distance as an index with the conventional example described later set to 100. A higher index indicates shorter braking distance on icy surfaces and superior ice performance.

[0133] Performance evaluation tests were conducted on 24 types of pneumatic tires, including a conventional pneumatic tire, which is an example of a conventional pneumatic tire, and Examples 1 to 23, which are pneumatic tires 1 according to the present invention. Of these, the conventional example has a notch in the center land area, but does not have a groove unit having a first groove, a second groove, and a third groove in the middle land area.

[0134] In contrast, in all of the examples of the pneumatic tire 1 according to the present invention, the notch 60 is arranged in the center land portion 21, and the groove unit 50 having a first groove 51, a second groove 52, and a third groove 53 is arranged in the middle land portion 22. Furthermore, the pneumatic tire 1 according to Examples 1 to 23 differs in the width Wc of the notch 60 relative to the width Wb of the center land portion 21, whether or not the shoulder main groove 35 extends in the tire circumferential direction and oscillates in the tire width direction, the inclination angle θ2 of the second groove 52 relative to the tire circumferential direction, the groove depth dr1 of the first groove 51 relative to the groove depth D of the circumferential main groove 30, the groove depth dr2 of the second groove 52 relative to the groove depth D of the circumferential main groove 30, the presence or absence of a wide sipe 71 adjacent to the width direction groove 40, and the sipe depth ds of the wide sipe 71 relative to the groove depth dr of the width direction groove 40.

[0135] Performance evaluation tests were conducted using these pneumatic tires 1, and as shown in Figures 13A and 13B, it was found that the pneumatic tires 1 according to Examples 1 to 23 can improve ice performance without reducing snow performance or wet performance compared to conventional examples. In other words, the pneumatic tires 1 according to Examples 1 to 23 can improve ice performance while suppressing the decline in snow performance and wet performance.

[0136] This disclosure encompasses the following inventions: Invention [1] A tread portion comprising a plurality of circumferential main grooves extending in the circumferential direction of the tire, a plurality of widthwise grooves extending in the width direction of the tire, and a plurality of land portions partitioned by the circumferential main grooves, wherein the plurality of circumferential main grooves comprises a shoulder main groove located on the outermost side in the width direction of the tire, and a center main groove adjacent to the shoulder main groove, and the plurality of land portions comprising a center land portion whose both sides in the width direction of the tire are partitioned by the center main groove, and a middle land portion whose both sides in the width direction of the tire are partitioned by the shoulder main groove and the center main groove, wherein the middle land portion comprises a first groove which is a widthwise groove extending in the width direction of the tire, with its inner end in the width direction of the tire communicating with the center main groove, and its outer end in the width direction of the tire terminating within the middle land portion, and a second groove which extends in the circumferential direction of the tire, with its end communicating with the first groove, A tire characterized in that a plurality of groove units are repeatedly arranged in the circumferential direction of the tire, each having a third groove which is a widthwise groove that extends in the tire width direction, with its inner end in the tire width direction communicating with the second groove and its outer end in the tire width direction communicating with the shoulder main groove, wherein the end of the second groove opposite to the end communicating with the first groove communicates with the first groove of an adjacent groove unit in the circumferential direction of the tire, and the center land portion has a plurality of notches which extend in the tire width direction, with one end communicating with the center main groove and the other end terminating within the center land portion. Invention [2] The tire according to Invention [1], wherein the notches communicate with the center main groove at a position within a range of 20% or less of the pitch length between adjacent first grooves in the circumferential direction of the tire, with respect to the position of the opening of the first groove relative to the center main groove in the tire circumferential direction. Invention [3] The tire according to Invention [1] or Invention [2], wherein the width Wc in the tire width direction of the notch is within the range of Wb × 0.3 ≤ Wc ≤ Wb × 0.9 with respect to the width Wb of the center land portion in the tire width direction. Invention [4] The tire according to any one of Inventions [1] to [3], wherein the shoulder main groove is formed extending in the tire circumferential direction and swinging in the tire width direction.Invention [5] A tire according to any one of Inventions [1] to [4], wherein the second groove has an inclination angle of 3° or more in the tire width direction with respect to the tire circumferential direction. Invention [6] A tire according to any one of Inventions [1] to [5], wherein the second groove has an inclination angle of 30° or less in the tire width direction with respect to the tire circumferential direction. Invention [7] A tire according to any one of Inventions [1] to [6], wherein the groove depth dr1 of the first groove is within the range of D × 0.8 ≤ dr1 ≤ D × 1.0 with respect to the groove depth D of the circumferential main groove. Invention [8] A tire according to any one of Inventions [1] to [7], wherein the groove depth dr3 of the third groove is within the range of D × 0.7 ≤ dr3 ≤ D × 0.9 with respect to the groove depth D of the circumferential main groove. Invention [9] The tire according to any one of Inventions [1] to [8], wherein the groove depth dr2 of the second groove is in the range of D × 0.5 ≤ dr2 ≤ D × 0.7 with respect to the groove depth D of the circumferential main groove. Invention

[10] The tire according to any one of Inventions [1] to [9], wherein the groove width of the center main groove is in the range of 3.0 mm or more and 10.0 mm or less, and the groove width of the first groove is in the range of 1.5 mm or more and 6.0 mm or less. Invention

[11] The tire according to any one of Inventions [1] to

[10] , wherein the groove width of the second groove is in the range of 1.5 mm or more and 5.0 mm or less, and the groove width of the third groove is in the range of 2.0 mm or more and 7.0 mm or less. Invention

[12] The middle land portion has a plurality of sipes extending in the tire width direction, the plurality of sipes having two or more types of sipes with different widths and including the widest sipe, the widest sipe is arranged adjacent to the widthwise groove, the tire according to any one of Inventions [1] to

[11] . Invention

[13] The widest sipe is the tire according to Invention

[12] , wherein the sipe depth ds is within the range of dr × 0.6 ≤ ds ≤ dr × 0.8 with respect to the groove depth dr of the widthwise groove. Invention

[14] The widest sipe is the tire according to Invention

[12] or Invention

[13] , wherein the widest sipe is arranged only on one side in the groove width direction of the adjacent widthwise groove.Invention

[15] The tire according to any one of Inventions

[12] to

[14] , wherein the wide sipe has a sipe width Wws within the range of Ws × 1.3 ≤ Wws ≤ Ws × 3.0 with respect to the sipe width ws of the sipes other than the wide sipe. Invention

[16] The tire according to any one of Inventions [1] to

[15] , wherein the tire is a winter tire or an all-season tire having a plurality of sipes extending in the tire width direction arranged on the land portion.

[0137] 1. Pneumatic tire 2. Tread section 3. Tread contact surface 4. Tread rubber 5. Shoulder section 8. Sidewall section 10. Bead section 11. Bead core 12. Bead filler 13. Carcass layer 14. Belt layer 16. Inner liner 17. Rim cushion rubber 18. Inner surface of tire 20. Land section 21. Center land section 22. Middle land section 23. Shoulder land section 30. Circumferential main groove 31. Center main groove 35. Shoulder main groove 40. Width direction groove 45. Shoulder width direction groove 50. Groove unit 51. First groove 52. Second groove 53. Third groove 60. Notch section 65. Middle notch section 70. Sipe 71. Wide sipe

Claims

1. A tire comprising: a plurality of circumferential main grooves arranged in the tread portion and extending in the circumferential direction of the tire; a plurality of widthwise grooves arranged in the tread portion and extending in the width direction of the tire; and a plurality of land portions partitioned by the circumferential main grooves, wherein the plurality of circumferential main grooves include: a shoulder main groove located on the outermost side in the width direction of the tire; and a center main groove adjacent to the shoulder main groove; and the plurality of land portions include: a center land portion partitioned on both sides in the width direction of the tire by the center main groove; and a middle land portion partitioned on both sides in the width direction of the tire by the shoulder main groove and the center main groove; wherein the middle land portion includes: a first groove which is a widthwise groove extending in the width direction of the tire, with its inner end in the width direction of the tire communicating with the center main groove and its outer end in the width direction of the tire terminating within the middle land portion; and a second groove which extends in the circumferential direction of the tire and whose end communicates with the first groove. A tire characterized in that a plurality of groove units are repeatedly arranged in the circumferential direction of the tire, each having a third groove which is a widthwise groove that extends in the tire width direction, with its inner end in the tire width direction communicating with the second groove and its outer end in the tire width direction communicating with the shoulder main groove, and the end of the second groove opposite to the end communicating with the first groove is communicating with the first groove of an adjacent groove unit in the circumferential direction of the tire, and the center land portion has a plurality of notches which extend in the tire width direction, with one end communicating with the center main groove and the other end terminating within the center land portion.

2. The tire according to claim 1, wherein the notch communicates with the center main groove at a position within a range of 20% or less of the pitch length between adjacent first grooves in the tire circumferential direction, with respect to the position of the opening of the first groove relative to the center main groove in the tire circumferential direction.

3. The tire according to claim 1, wherein the width Wc of the notch in the tire width direction is within the range of Wb × 0.3 ≤ Wc ≤ Wb × 0.9 with respect to the width Wb of the center land portion in the tire width direction.

4. The tire according to claim 1, wherein the shoulder main groove is formed extending in the circumferential direction of the tire and swinging in the width direction of the tire.

5. The tire according to claim 1, wherein the second groove has an inclination angle of 3° or more in the tire width direction with respect to the tire circumferential direction.

6. The tire according to claim 1, wherein the second groove has an inclination angle of 30° or less in the tire width direction with respect to the tire circumferential direction.

7. The tire according to claim 1, wherein the groove depth dr1 of the first groove is within the range of D × 0.8 ≤ dr1 ≤ D × 1.0 with respect to the groove depth D of the circumferential main groove.

8. The tire according to claim 1, wherein the groove depth dr3 of the third groove is within the range of D × 0.7 ≤ dr3 ≤ D × 0.9 with respect to the groove depth D of the circumferential main groove.

9. The tire according to claim 1, wherein the groove depth dr2 of the second groove is within the range of D × 0.5 ≤ dr2 ≤ D × 0.7 with respect to the groove depth D of the circumferential main groove.

10. The tire according to claim 1, wherein the center main groove has a groove width in the range of 3.0 mm to 10.0 mm, and the first groove has a groove width in the range of 1.5 mm to 6.0 mm.

11. The tire according to claim 1, wherein the second groove has a groove width in the range of 1.5 mm to 5.0 mm, and the third groove has a groove width in the range of 2.0 mm to 7.0 mm.

12. The tire according to claim 1, wherein the middle land portion has a plurality of sipes extending in the tire width direction, the plurality of sipes having two or more types of sipes with different widths and including the widest sipe, and the widest sipe is arranged adjacent to the widthwise groove.

13. The tire according to claim 12, wherein the wide sipe has a sipe depth ds within the range of dr × 0.6 ≤ ds ≤ dr × 0.8 with respect to the groove depth dr of the widthwise groove.

14. The tire according to claim 12, wherein the wide sipe is arranged only on one side in the groove width direction of adjacent widthwise grooves.

15. The tire according to claim 12, wherein the wide sipe has a sipe width Wws within the range of Ws × 1.3 ≤ Wws ≤ Ws × 3.0 with respect to the sipe width ws of the sipes other than the wide sipe.

16. The tire according to claim 1, wherein the tire is a winter tire or an all-season tire having a plurality of sipes extending in the tire width direction arranged on the land portion.

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