阅读说明：本技术 充气轮胎 (Pneumatic tire ) 是由 中崎敬介 于 2019-01-07 设计创作，主要内容包括：在充气轮胎中,内侧胎肩主槽(21)的槽开口部和内侧中央主槽(22)的槽开口部具有直线形状的边缘部,并且外侧中央主槽(23)的槽开口部具有被倒角为锯齿形状的边缘部。此外,内侧胎肩主槽(21)的槽宽Wg1、内侧中央主槽(22)的槽宽Wg2以及外侧中央主槽(23)的槽宽Wg3具有Wg1＜Wg3和Wg2＜Wg3的关系。(In the pneumatic tire, the groove opening of the inner shoulder main groove (21) and the groove opening of the inner center main groove (22) have linear edge portions, and the groove opening of the outer center main groove (23) has an edge portion chamfered in a zigzag shape. Further, the groove width Wg1 of the inner shoulder main groove (21), the groove width Wg2 of the inner center main groove (22), and the groove width Wg3 of the outer center main groove (23) have the relationships Wg1< Wg3 and Wg2< Wg 3.)

1. A pneumatic tire is provided with: an attachment direction display portion that displays an attachment direction of the tire with respect to the vehicle; an inner shoulder main groove and an inner center main groove formed in a region on the inner side in the vehicle width direction with respect to the tire equatorial plane as a boundary and extending in the tire circumferential direction; an outer central main groove formed in a region on the outer side in the vehicle width direction and extending in the tire circumferential direction; a circumferential narrow groove formed on the outer side in the tire width direction than the outer center main groove and extending in the tire circumferential direction; and a five-row land portion partitioned by the four grooves, wherein the groove opening portion of the inner-shoulder main groove and the groove opening portion of the inner-center main groove have linear edge portions, the groove opening portion of the outer-center main groove has an edge portion chamfered in a zigzag shape, and the groove width Wg1 of the inner-shoulder main groove, the groove width Wg2 of the inner-center main groove, and the groove width Wg3 of the outer-center main groove have relationships Wg1< Wg3 and Wg2< Wg 3.

2. The pneumatic tire of claim 1 wherein the groove widths Wg1, Wg2, and Wg3 have relationships 0.70 ≦ Wg1/Wg3 ≦ 0.90 and 0.70 ≦ Wg2/Wg3 ≦ 0.90.

3. The pneumatic tire as claimed in claim 1 or 2, wherein the groove widths Wg1, Wg2, and Wg3 have a relationship Wg1< Wg2< Wg 3.

4. The pneumatic tire according to any one of claims 1 to 3,

the groove width Wg4 of the circumferential narrow groove is in the range of 0.10 Wg4/Wg3 to 0.35 with respect to the groove width Wg3 of the outer central main groove.

5. The pneumatic tire as claimed in claim 4, wherein the groove width Wg4 and the groove depth Hg4 of the circumferential fine groove are in the range of 1.5mm ≦ Wg4 ≦ 4.0mm and 5.0mm ≦ Hg4 ≦ 7.5 mm.

6. The pneumatic tire as claimed in claim 5, wherein the groove width Wg4 and the groove depth Hg4 of the circumferential fine groove are in the range of 3.0mm ≦ Wg4 and 6.7mm ≦ Hg 4.

7. The pneumatic tire according to any one of claims 1 to 6, wherein a distance Dg1 from the tire equatorial plane to the inner shoulder main groove, a distance Dg2 from the tire equatorial plane to the inner center main groove, and a distance Dg3 from the tire equatorial plane to the outer center main groove have relationships of 0.26. ltoreq. Dg 1/TW. ltoreq.0.33, 0.10. ltoreq. Dg 2/TW. ltoreq.0.15, and 0.10. ltoreq. Dg 3/TW. ltoreq.0.15 with respect to the tire ground contact width TW.

8. The pneumatic tire as claimed in any one of claims 1 to 7, wherein the zigzag shape of the outer side center main groove is formed by a plurality of chamfered portions formed at the edge portion of the groove opening portion, and a depth Hc of the chamfered portions has a relationship of 0.30 ≦ Hc/Hg3 ≦ 0.50 with respect to a groove depth Hg3 of the outer side center main groove.

9. The pneumatic tire according to any one of claims 1 to 8, wherein the land portion defined by the outer central main groove and the circumferential narrow groove includes: and a curved lug groove extending inward in the tire width direction from the circumferential narrow groove, curved in a hook shape in the tire circumferential direction, and terminating in the land portion.

10. The pneumatic tire according to any one of claims 1 to 9, wherein a land portion on the outer side in the tire width direction defined by the inner-shoulder main groove includes: an inner shoulder lug groove extending from the tire ground contact end inward in the tire width direction, terminating in the inner shoulder land portion, and inclined at a predetermined inclination angle with respect to the tire circumferential direction,

the zigzag shape of the outer central main groove is formed by alternately connecting long strip portions and short strip portions,

the inclination direction of the elongated portion of the zigzag shape with respect to the tire circumferential direction is opposite to the inclination direction of the inner shoulder lug groove.

11. The pneumatic tire according to any one of claims 1 to 10, wherein the land portion defined by the inner-side central main groove and the outer-side central main groove includes: a central lug groove extending from the inner central main groove toward the tire equatorial plane side, terminating in the central land portion without intersecting the tire equatorial plane, and,

the distance D3 between the end of the center lug groove and the tire equatorial plane is within the range of 1.0mm < D3.

12. The pneumatic tire according to any one of claims 1 to 11, wherein the land portion defined by the inner-side central main groove and the outer-side central main groove includes: a plurality of center lug grooves extending from the inner center main groove toward the tire equatorial plane side and terminating in the center land portion,

a pitch length P32 of the zigzag shape of the outer central main groove has a relationship P31< P32 with respect to a pitch length P31 of the plurality of central lug grooves.

13. The pneumatic tire according to any one of claims 1 to 10, wherein the inner second land portion includes: an inner second sipe extending outward in the tire width direction from the inner center main groove and terminating in the inner second land portion,

the center land portion includes: and a center lug groove extending from the inner center main groove toward the tire equatorial plane side and terminating in the center land portion.

14. The pneumatic tire of claim 13, wherein all of the central sipes are configured to be offset in the same direction in the tire circumferential direction with respect to an extension line of the inner second sipe.

15. The pneumatic tire according to any one of claims 1 to 14, wherein the land portion on the outer side in the tire width direction divided by the inner-shoulder main groove is a rib having a tread surface continuous in the tire circumferential direction.

Technical Field

The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire capable of achieving both dry performance and wet performance of the tire.

Background

In recent pneumatic tires, there is a demand that the driving stability performance on dry road surfaces should be compatible with the driving stability performance on wet road surfaces. As conventional pneumatic tires for solving this problem, there are known techniques described in patent documents 1 and 2.

Disclosure of Invention

Problems to be solved by the invention

The present invention aims to provide a pneumatic tire that can achieve both dry performance and wet performance of the tire.

Technical scheme

In order to achieve the above object, a pneumatic tire according to the present invention includes: an attachment direction display portion that displays an attachment direction of the tire with respect to the vehicle; an inner shoulder main groove and an inner center main groove formed in a region on the inner side in the vehicle width direction with respect to the tire equatorial plane as a boundary and extending in the tire circumferential direction; an outer central main groove formed in a region on the outer side in the vehicle width direction and extending in the tire circumferential direction; a circumferential narrow groove formed on the outer side in the tire width direction than the outer center main groove and extending in the tire circumferential direction; and a five-row land portion partitioned by the four grooves, wherein the groove opening portion of the inner-shoulder main groove and the groove opening portion of the inner-center main groove have linear edge portions, the groove opening portion of the outer-center main groove has an edge portion chamfered in a zigzag shape, and the groove width Wg1 of the inner-shoulder main groove, the groove width Wg2 of the inner-center main groove, and the groove width Wg3 of the outer-center main groove have relationships Wg1< Wg3 and Wg2< Wg 3.

Effects of the invention

In the pneumatic tire of the present invention, (1) two main grooves are arranged in the vehicle width direction inner region, and one main groove and one circumferential narrow groove are arranged in the vehicle width direction outer region, so that it is possible to ensure the water drainage property in the vehicle width direction inner region having a high contribution to wet performance, and to ensure the rigidity in the vehicle width direction outer region having a high contribution to dry performance. Further, (2) the two main grooves in the vehicle width direction inner region have a straight line shape, and the main groove in the vehicle width direction outer region has a chamfered portion having a zigzag shape, so that the groove volume of the main groove in the vehicle width direction outer region can be relatively enlarged. This ensures the groove volume in the region outside the vehicle width direction, and ensures the wet performance of the tire. Further, (3) the groove width Wg3 of the main groove in the vehicle width direction outer region is larger than the groove widths Wg1 and Wg2 of the two main grooves in the vehicle width direction inner region, and therefore the groove volume in the vehicle width direction outer region can be secured, and the wet performance of the tire can be secured. This provides an advantage of properly satisfying both wet performance and dry performance of the tire.

Drawings

Fig. 1 is a cross-sectional view showing a tire meridian direction of a pneumatic tire according to an embodiment of the present invention.

Fig. 2 is a plan view showing a tread surface of the pneumatic tire shown in fig. 1.

Fig. 3 is an enlarged view showing a main portion of a region on the tread surface shown in fig. 2 on the inner side in the vehicle width direction.

FIG. 4 is a top view showing an inboard shoulder sipe and an inboard second lug.

FIG. 5 is a cross-sectional view in the depth direction of the inboard shoulder sipe and the inboard second lug groove illustrated in FIG. 4.

Fig. 6 is an enlarged view showing a main portion of a region on the tread surface shown in fig. 2, the region being on the inner side in the vehicle width direction.

Fig. 7 is an enlarged view showing the inner second land portion and the central land portion shown in fig. 6.

Fig. 8 is a perspective view showing a chamfered portion of the center land portion shown in fig. 6.

Fig. 9 is an enlarged view showing a main portion of an area on the tread surface shown in fig. 2, the area being located on the outer side in the vehicle width direction.

Fig. 10 is an enlarged view showing the outer second land portion and the outer shoulder land portion shown in fig. 9.

Fig. 11 is a sectional view in the depth direction of the curved lug groove and the first outer shoulder lug groove shown in fig. 10.

Fig. 12 is an explanatory view showing a modification of the lug groove shown in fig. 4 and 7.

Fig. 13 is an explanatory view showing a modification of the inner second lug groove shown in fig. 4.

Fig. 14 is an explanatory view showing a modification of the first outer shoulder lug groove shown in fig. 9.

Fig. 15 is a graph showing the results of a performance test of the pneumatic tire according to the embodiment of the present invention.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings. The present invention is not limited to the embodiments. The constituent elements of the present embodiment include those that can be replaced or obviously replaced while maintaining the identity of the invention. Further, a plurality of modification examples described in the present embodiment can be arbitrarily combined within a range which is obvious to those skilled in the art.

[ pneumatic tires ]

Fig. 1 is a cross-sectional view showing a tire meridian direction of a pneumatic tire according to an embodiment of the present invention. This figure shows a cross-sectional view of one side region in the tire radial direction. In the figure, a radial tire for a passenger car is shown as an example of the pneumatic tire.

In fig. 1, the cross section in the tire meridian direction is a cross section when the tire is cut on a plane including a tire rotation axis (not shown). Note that the symbol CL is a tire equatorial plane and refers to a plane that passes through the center point of the tire in the tire rotation axis direction and is perpendicular to the tire rotation axis. The tire width direction means a direction parallel to the tire rotation axis, and the tire radial direction means a direction perpendicular to the tire rotation axis.

Further, the vehicle width direction inner side and the vehicle width direction outer side are defined as the orientations with respect to the vehicle width direction when the tire is attached to the vehicle. Further, left and right regions bounded by the tire equatorial plane are defined as a vehicle width direction outer region and a vehicle width direction inner region, respectively. Further, the pneumatic tire is provided with an attachment direction display portion (not shown) that displays the attachment direction of the tire to the vehicle. The attachment direction display portion is constituted by, for example, a mark or a projection and a recess attached to a sidewall portion of the tire. For example, ECER30 (article 30 of the european economic commission regulation) specifies that a display portion of a vehicle attachment direction must be provided to a side wall portion that becomes the outer side in the vehicle width direction in a vehicle attached state.

The pneumatic tire 10 has an annular structure centered on a tire rotation axis, and includes: a pair of bead cores 11, 11; a pair of bead cores 12, 12; a carcass layer 13; a belt layer 14; a tread rubber 15; a pair of sidewall rubbers 16, 16; and a pair of rim cushion rubbers 17, 17 (see fig. 1). In fig. 1, reference numeral 20 denotes a rim of a wheel.

The pair of bead cores 11, 11 are formed by annularly and multiply winding one or more bead wires made of steel, and are embedded in the bead portions to constitute cores of the left and right bead portions. The pair of bead fillers 12, 12 are disposed on the outer peripheries of the pair of bead cores 11, 11 in the tire radial direction, respectively, to reinforce the bead portions.

The carcass layer 13 has a single-layer structure including a single ply or a multilayer structure in which a plurality of plies are laminated, and is annularly disposed between the left and right bead cores 11, 11 to constitute a carcass of the tire. Both ends of the carcass layer 13 are locked by being wound around the outside in the tire width direction so as to wrap the bead core 11 and the bead filler 12. The carcass layer 13 is formed by applying a rubber coating to a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon, or the like) and rolling the cords, and has a carcass angle (defined as an inclination angle of the longitudinal direction of the carcass cord with respect to the tire circumferential direction) of 80(deg) to 95(deg) in absolute value.

The belt layer 14 is formed by laminating a pair of intersecting belts 141 and 142 and a belt cover layer 143, and is disposed so as to surround the outer periphery of the carcass layer 13. The pair of cross belts 141, 142 are formed by coating a plurality of belt cords made of steel or an organic fiber material with a rubber coating and rolling the coated cords, and have a belt angle of 20(deg) or more and 55(deg) or less in absolute value. Further, the pair of intersecting belts 141, 142 have belt layer angles (defined as the inclination angle of the long dimension direction of the belt cord with respect to the tire circumferential direction) of mutually different signs, and the long dimension directions of the belt cords are alternately laminated with each other (so-called an oblique crossing structure). The belt cover layer 143 is formed by covering a belt cord made of steel or an organic fiber material with a coating rubber, and has a belt angle of 0(deg) or more and 10(deg) or less in absolute value. The belt cover layer 143 is a tape formed by covering one or more belt cords with a coating rubber, for example, and is formed by spirally winding the tape a plurality of times in the tire circumferential direction with respect to the outer circumferential surfaces of the cross belts 141, 142.

The tread rubber 15 is disposed on the outer periphery of the carcass layer 13 and the belt layer 14 in the tire radial direction, and constitutes a tread portion of the tire. The pair of sidewall rubbers 16, 16 are disposed on the outer sides of the carcass layer 13 in the tire width direction, respectively, and constitute left and right sidewall portions. The pair of rim cushion rubbers 17, 17 are disposed on the inner sides in the tire radial direction of the turnback portions of the left and right bead cores 11, 11 and the carcass layer 13, respectively, and constitute rim fitting surfaces of the bead portions.

[ Tread pattern ]

Fig. 2 is a plan view showing a tread surface of the pneumatic tire shown in fig. 1. The figure shows the tread pattern of a tire for all seasons. In the figure, the tire circumferential direction refers to a direction around the tire rotation axis. Note that, symbol T is a tire ground contact end, and a size TW is a tire ground contact width.

As shown in FIG. 2, the pneumatic tire 10 has a plurality of circumferential grooves 21 to 24 extending in the tire circumferential direction on the tread surface, and a plurality of land portions 31 to 35 defined by the circumferential grooves 21 to 24.

The main groove means a groove having a display function of a wear indicator specified by JATMA (Japan automatic Tire Manufacturers association). The cross-groove described later is a cross-groove extending in the tire width direction, and is opened when the tire contacts the ground to function as a groove. The sipe described later is a cut groove formed in the tread surface and is closed when the tire contacts the ground.

In a no-load state in which the tire is attached to a predetermined rim and a predetermined internal pressure is applied, the groove width is measured as the maximum value of the distance between the left and right groove walls of the groove opening. In the configuration in which the land portion has the notch portion and the chamfered portion at the edge portion, the groove width is measured with an intersection point of extension lines of the tread surface and the groove wall as a measurement point when viewed in a cross-section with the groove longitudinal direction as a normal direction. In the configuration in which the groove extends in a zigzag or wavy manner in the tire circumferential direction, the groove width is measured with the center line of the amplitude of the groove wall as a measurement point.

In a no-load state where the tire is attached to a predetermined rim and a predetermined internal pressure is applied, the groove depth is measured as the maximum value of the distance from the tread surface to the groove bottom. In the structure in which the groove bottom has a partial uneven portion or sipe, the groove depth was measured except for these.

The predetermined Rim is a "standard Rim" defined by JATMA, a "Design Rim" defined by TRA, or a "Measuring Rim" defined by ETRTO. The predetermined internal pressure is the maximum value of "maximum air pressure" defined by JATMA, "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined by TRA, or "INFLATION PRESSURES" defined by ETRTO. The predetermined LOAD is a "maximum LOAD CAPACITY" defined by JATMA, a maximum value of "LOAD conditions AT variaous COLD stability requirements" defined by TRA, or "LOAD CAPACITY" defined by ETRTO. However, in JATMA, in the case of a passenger tire, the predetermined internal pressure is 180(kPa) in pressure and the predetermined load is 88 (%) of the maximum load capacity at the predetermined internal pressure.

For example, in the configuration of fig. 2, the pneumatic tire 10 has a tread pattern that is asymmetric in the left and right directions with respect to the tire equatorial plane CL as the center. The inner region in the vehicle width direction, which is bounded by the tire equatorial plane CL, has two circumferential main grooves 21, 22, and the outer region in the vehicle width direction has one circumferential main groove 23 and one circumferential narrow groove 24. The circumferential grooves 21 to 24 are arranged symmetrically with respect to the tire equatorial plane CL. Five rows of land portions 31 to 35 are defined by the circumferential grooves 21 to 24. The one-row land portion 33 is disposed on the tire equatorial plane CL. Here, of the two circumferential main grooves 21, 22 located in the vehicle width direction inner region, the circumferential main groove 21 located on the tire ground contact edge T side is referred to as an inner shoulder main groove. The circumferential main groove 23 located on the tire equatorial plane CL side is referred to as an outer center main groove.

Further, the groove width Wg1 of the inner-shoulder main groove 21, the groove width Wg2 of the inner-center main groove 22, and the groove width Wg3 of the outer-center main groove 23 have a relationship of Wg1< Wg3 and Wg2< Wg3, preferably, a relationship of Wg1< Wg2< Wg 3. Specifically, the groove widths Wg1, Wg2, and Wg3 have the relationships 0.70. ltoreq. Wg1/Wg 3. ltoreq.0.90 and 0.70. ltoreq. Wg2/Wg 3. ltoreq.0.90. Further, the groove width Wg3 of the outer center main groove 23 having the widest width is in the range of 10.0(mm) Wg3 (mm) to 14.0 (mm). The main grooves 21 to 23 have groove depths Hg1 to Hg3 within a range of 6.0(mm) to 9.0 (mm).

The width Wg4 of the narrow circumferential groove 24 is narrower than the widths Wg 1-Wg 3 of the main grooves 21-23, and is in the range of 1.5(mm) to Wg4 (mm) to 4.0 (mm). The groove width Wg4 of the circumferential narrow groove 24 is in the range of 0.10. ltoreq. Wg4/Wg 3. ltoreq.0.35 with respect to the groove width Wg3 of the outer center main groove 23. Further, the groove depth Hg4 of the circumferential narrow groove 24 is in the range of 5.0 (mm). ltoreq.Hg 4.ltoreq.7.5 (mm). When the groove width Wg4 and the groove depth Hg4 of the circumferential narrow groove 24 are in the ranges of 3.0 (mm). ltoreq.Wg 4 and 6.7 (mm). ltoreq.Hg 4, the wear indicator may be formed with the circumferential narrow groove 24 as a main groove.

In the above configuration, (1) the two main grooves 21, 22 are arranged in the vehicle width direction inside region, and the one main groove 23 and the one circumferential narrow groove 24 are arranged in the vehicle width direction outside region, so that the water drainage property of the vehicle width direction inside region having a high contribution to the wet performance can be ensured, and the rigidity of the vehicle width direction outside region having a high contribution to the dry performance can be ensured. Further, (2) since the two main grooves 21, 22 in the vehicle width direction inside region have a straight line shape and the main groove 23 in the vehicle width direction outside region has the chamfered portions 332, 343 (see fig. 6 and 9) having a zigzag shape, the groove volume of the main groove 23 in the vehicle width direction outside region can be relatively enlarged. This ensures the groove volume in the region outside the vehicle width direction, and ensures the wet performance of the tire. Further, (3) the groove width Wg3 of the main groove 23 in the vehicle width direction outer region is larger than the groove widths Wg1 and Wg2 of the two main grooves 21 and 22 in the vehicle width direction inner region, and therefore the groove volume in the vehicle width direction outer region can be secured, and the wet performance of the tire can be secured. This provides an advantage of properly satisfying both wet performance and dry performance of the tire.

In addition, in FIG. 2, the distance Dg1 from the tire equatorial plane CL to the inner shoulder main groove 21, the distance Dg2 from the tire equatorial plane CL to the inner center main groove 22, and the distance Dg3 from the tire equatorial plane CL to the outer center main groove 23 have the relationships of 0.26. ltoreq. Dg 1/TW. ltoreq.0.33, 0.10. ltoreq. Dg 2/TW. ltoreq.0.15, and 0.10. ltoreq. Dg 3/TW. ltoreq.0.15 with respect to the tire ground contact width TW. Further, the distance Dg4 from the tire equatorial plane CL to the circumferential narrow groove 24 has a relationship of 0.26. ltoreq. Dg 4/TW. ltoreq.0.33 with respect to the tire ground contact width TW.

In a no-load state where the tire is attached to a prescribed rim and filled with a prescribed internal pressure, the distances Dg1 to Dg3 of the main grooves are measured as the distances from the equatorial plane of the tire to the groove center line of the main groove.

The groove center line of the circumferential main groove is defined as: the center point of the left and right measurement points across the groove width of the circumferential main groove is a straight line parallel to the tire circumferential direction.

The tire ground contact width TW was determined as: the maximum linear distance in the tire axial direction of the contact surface of the tire and the flat plate when the tire is attached to a prescribed rim and a prescribed internal pressure is applied while being placed vertically with respect to the flat plate in a stationary state and a load corresponding to a prescribed load is applied.

The tire ground contact end T is defined as: the tire has a maximum width position in the tire axial direction of a contact surface of the tire and the flat plate when the tire is attached to a prescribed rim and a prescribed internal pressure is applied while being placed vertically with respect to the flat plate in a stationary state and a load corresponding to a prescribed load is applied.

Further, a region located on the tire equatorial plane CL side with the shoulder main groove 21 and the circumferential narrow groove 24 as a boundary is referred to as a center region, and regions located on the left and right sides of the tire ground contact edge T side are referred to as shoulder regions.

The land portions 31 and 35 on the outer side in the tire width direction defined by the shoulder main groove 21 and the circumferential narrow groove 24 are defined as shoulder land portions. The shoulder land portions 31 and 35 are the outermost land portions in the tire width direction and are located on the tire ground contact end T. The shoulder land portion 31 located in the vehicle width direction inner side region is defined as an inner shoulder land portion, and the shoulder land portion 35 located in the vehicle width direction outer side region is defined as an outer shoulder land portion.

The land portions 32 and 34 on the inner side in the tire width direction defined by the shoulder main groove 21 and the circumferential narrow groove 24 are defined as second land portions. Therefore, the second land portions 32 and 34 are adjacent to the shoulder land portions 31 and 35 via the shoulder main grooves 21 and 24. The second land portion 32 located in the vehicle width direction inside region is defined as an inside second land portion, and the second land portion 34 located in the vehicle width direction outside region is defined as an outside second land portion.

Further, the land portion 33 located between the second land portions 32, 34 is defined as a central land portion. The central land portion 33 is disposed on the tire equatorial plane CL.

In the configuration of fig. 2, the groove area ratio in the tire contact patch is in the range of 18% to 30%. Thus, the dry performance and wet performance of the tire can be balanced.

The slot area ratio is defined by slot area/(slot area + ground area). The slot area refers to the open area of the slot of the ground plane. The grooves refer to circumferential grooves and cross grooves of the tread portion, and do not include sipes, cuts, notches, and the like. The contact area was measured as the contact area between the tire and the road surface. Further, the groove area and the ground contact area are measured by a contact surface between the tire and the flat plate when the tire is attached to a predetermined rim and a predetermined internal pressure is applied, while the tire is placed vertically with respect to the flat plate in a stationary state, and a load corresponding to a predetermined load is applied.

Inner tire shoulder ring bank part

Fig. 3 is an enlarged view showing a main portion of a region on the tread surface shown in fig. 2 on the inner side in the vehicle width direction. The figure shows the inboard shoulder land 31 and the inboard second land 32 in particular in an enlarged scale. FIG. 4 is a top view showing an inboard shoulder sipe and an inboard second lug. FIG. 5 is a cross-sectional view in the depth direction of the inboard shoulder sipe and the inboard second lug groove illustrated in FIG. 4.

As shown in fig. 3, the inboard shoulder land portion 31 includes a plurality of inboard shoulder rib grooves 311 and a plurality of inboard shoulder sipes 312.

The inner shoulder lug groove 311 extends inward in the tire width direction from the tire ground contact edge T, is not connected to the inner shoulder main groove 21, and terminates in the ground contact surface of the inner shoulder land portion 31. Further, the plurality of inner shoulder lug grooves 311 are arranged at a predetermined pitch length in the tire circumferential direction. In the configuration of fig. 3, the inner shoulder lug groove 311 has an arc shape gently curved in the tire circumferential direction, but the inner shoulder lug groove 311 is not limited thereto, and may have a straight shape or a curved shape (not shown). The groove width Wg11 (see FIG. 3) of the inner-shoulder lug grooves 311 is in the range of 1.5 (mm). ltoreq.Wg 11. ltoreq.4.5 (mm), and the groove depth Hg11 (not shown) is in the range of 0.55. ltoreq. Hg11/Hg 1. ltoreq.0.80 with respect to the groove depth Hg1 (see FIG. 5) of the inner-shoulder main grooves 21. The inclination angle θ 11 (see FIG. 3) of the inner shoulder lug grooves 311 with respect to the tire circumferential direction is in the range of 75 (deg). ltoreq.θ 11. ltoreq.105 (deg). This reduces pattern noise of the tire.

The groove width and groove depth of the shoulder lug groove were measured as: maximum slot width and maximum slot depth in the ground plane.

The inclination angle of the lug groove was measured as: an angle formed by a straight line connecting both end portions of the lug groove in the tire ground contact surface and the tire circumferential direction.

The inner shoulder sipes 312 extend outward in the tire width direction from the inner shoulder main groove 21, do not intersect the tire ground contact edge T, and terminate in the ground contact surface of the inner shoulder land portion 31. Further, a single inboard shoulder sipe 312 is disposed between the adjacent inboard shoulder sipes 311, 311. Therefore, the inboard shoulder lug grooves 311 and the inboard shoulder sipes 312 are alternately arranged in the tire circumferential direction. As a result, compared with a configuration in which only the lug grooves or only the sipes are arranged in the tire circumferential direction, it is possible to balance wet performance and dry performance of the tire and reduce pattern noise of the tire.

In the configuration of fig. 3, the inner shoulder sipes 312 have a straight shape or a gently curved arc shape, and extend obliquely in parallel to the inner shoulder sipes 311. The sipe width Wg12 (see FIG. 4) of the inner shoulder sipe 312 is in the range of 0.6 (mm). ltoreq.Wg 12.ltoreq.1.8 (mm), and the sipe depth Hg12 (see FIG. 5) is in the range of 3.0 (mm). ltoreq.Hg 12.ltoreq.7.0 (mm). Thus, the inboard shoulder sipes 312 are appropriately closed when the tire is grounded. The inclination angle θ 12 of the inner shoulder sipe 312 (see FIG. 4) with respect to the tire circumferential direction is set to 55 (deg). ltoreq.θ 12. ltoreq.80 (deg).

In a no-load state where the tire was attached to a prescribed rim and filled with a prescribed internal pressure, the sipe width was measured as: the maximum value of the opening width of the sipe on the tread surface of the land portion.

In a no-load state where the tire was attached to a prescribed rim and filled with a prescribed internal pressure, the sipe depth was measured as: the maximum distance from the tread surface to the sipe bottom. In the configuration in which the sipe has a partial uneven portion at the groove bottom, the sipe depth is measured excluding the uneven portion.

Further, the extension length L12 (see FIG. 3) of the inside shoulder sipe 312 in the tire width direction and the ground contact width W1 (see FIG. 3) of the inside shoulder land portion 31 preferably have a relationship of 0.35. ltoreq.L 12/W1. ltoreq.0.60, and more preferably have a relationship of 0.40. ltoreq.L 12/W1. ltoreq.0.55. The lower limit ensures the water removal function of the shoulder sipes 312 and improves the wet performance of the tire, and the upper limit ensures the rigidity of the shoulder land portion 31 and ensures the dry performance of the tire.

The ground width of the land portion was measured as: a maximum linear distance in a tire axial direction of a contact surface of the land portion and the flat plate when the tire is attached to a predetermined rim and a predetermined internal pressure is applied while being placed vertically with respect to the flat plate in a stationary state and a load corresponding to a predetermined load is applied.

In the configuration of fig. 3, the inner-shoulder land portion 31 is a rib continuous in the tire circumferential direction, and is cut in the tire circumferential direction or the tire width direction by a groove or a sipe, specifically, as described above, the inner-shoulder rib groove 311 and the inner-shoulder sipe 312 do not cross the inner-shoulder land portion 31 and are not connected to each other. Therefore, the ground contact surface of the inner shoulder land portion 31 is continuous in the tire circumferential direction.

In fig. 4, the inner shoulder lug grooves 311 and the inner shoulder sipes 312 are arranged so as to overlap (overlap) each other in the tire width direction. Further, the tire width direction distance D1 at the overlapping portion of the inner shoulder lug groove 311 and the inner shoulder sipe 312 preferably has a relationship of 0.15. ltoreq.D 1/W1. ltoreq.0.35, more preferably 0.20. ltoreq.D 1/W1. ltoreq.0.30, with respect to the ground contact width W1 of the inner shoulder land portion 31. This ensures the rigidity of the inner shoulder land portion 32, and ensures the dry performance of the tire.

Inner second land portion

As shown in fig. 3, the inner second land portion 32 includes a plurality of inner second sipes 322 and a plurality of inner second cross grooves 321.

The inner second lug groove 321 extends from the inner shoulder main groove 21 inward in the tire width direction, does not connect to the inner center main groove 22, and terminates in the inner second land portion 32. Further, a plurality of inner second lug grooves 321 are arranged in the tire circumferential direction at the same pitch as the inner shoulder lug grooves 311 and the inner shoulder sipes 312. In the configuration of fig. 3, the inner second lug groove 321 has an arc shape that is gently curved in the tire circumferential direction, but the present invention is not limited thereto, and the inner second lug groove 321 may have a straight shape or a curved shape (not shown).

In the above configuration, (1) the inner-shoulder sipes 312 open from the tire ground contact edge T side to the inner-shoulder main grooves 21, and the inner-second lug grooves 321 open from the tire equatorial plane CL side to the inner-shoulder main grooves 21 (see fig. 2). Therefore, compared with the configuration in which both are sipes, the water drainage property of the inner region of the tread in the vehicle width direction can be improved, and the wet performance of the tire can be improved. Further, as compared with the configuration in which both are the lug grooves, the rigidity of the inner region of the tread in the vehicle width direction can be secured, and the dry performance of the tire can be improved. Therefore, the wet performance and the dry performance of the tire are considered at the same time. Further, (2) since the inside shoulder sipes 312 and the inside second lug grooves 321 have a semi-closed structure terminating inside the land portions 31 and 32, the rigidity of the land portions 31 and 32 can be secured, and the dry performance of the tire can be improved.

Further, the groove width Wg21 (see FIG. 4) of the inner second lug groove 321 is in the range of 1.5 (mm). ltoreq.Wg 21. ltoreq.4.5 (mm), and the groove depth Hg21 (see FIG. 5) is in the range of 0.55. ltoreq. Hg21/Hg 1. ltoreq.0.80 with respect to the groove depth Hg1 (see FIG. 5) of the inner shoulder main groove 21. Further, the inclination angle θ 21 (see fig. 4) of the inner second lug groove 321 with respect to the tire circumferential direction is in the range of 55(deg) ≦ θ 21 ≦ 80 (deg). The occurrence of chipping wear can be suppressed by the above lower limit, and the wet rotation performance of the tire can be ensured by the above upper limit.

Further, in FIG. 3, the extension length L21 of the inner second lug groove 321 in the tire width direction and the ground contact width W2 of the inner second land portion 32 preferably have a relationship of 0.50. ltoreq.L 21/W2. ltoreq.0.80, and more preferably have a relationship of 0.60. ltoreq.L 21/W2. ltoreq.0.70. The lower limit ensures the water removal performance of the inner second lug groove 321, thereby improving the wet performance of the tire, and the upper limit ensures the rigidity of the inner second land portion 32, thereby ensuring the dry performance of the tire.

In the configuration of fig. 3, the inner second lug groove 321 and the inner shoulder lug groove 311 and the inner shoulder sipe 312 of the inner shoulder land portion 31 are inclined in the same direction with respect to the tire circumferential direction. Thereby, the drainage of the tire is improved. Further, the inner second lug groove 321 is arranged so as not to overlap the inner shoulder lug groove 311 in the tire circumferential direction (see the broken line in fig. 3). Specifically, the inner second lug grooves 321 are arranged so as not to intersect with the inner shoulder lug grooves 311 in a view projected in the tire width direction and so as to be separated from each other in the tire circumferential direction. Thereby, pattern noise of the tire is reduced.

Further, as shown in fig. 3, the inboard second lug groove 321 is arranged to be offset in the tire circumferential direction with respect to an extension of the inboard shoulder sipe 312. In the configuration of fig. 3, all the inside second lug grooves 321 are arranged offset in the tire circumferential direction with respect to the extension of the inside shoulder sipe 312, and are also offset to the opposite side with respect to the inclination direction of the groove center line of the inside shoulder sipe 312. Further, in FIG. 4, the distance G1 in the tire circumferential direction between the opening position of the inner shoulder sipe 312 with respect to the inner shoulder main groove 21 and the opening position of the inner second lug groove 321 with respect to the inner shoulder main groove 21 preferably has a relationship of 1.50. ltoreq.G 1/Wg 21. ltoreq.4.00, more preferably 2.00. ltoreq.G 1/Wg 21. ltoreq.3.50 with respect to the groove width Wg21 of the inner second lug groove 321. Thereby, pattern noise of the tire is reduced.

As shown in fig. 5, the inner second lug groove 321 includes a bottom elevated portion 3211 and a slit 3212.

The raised bottom portion 3211 is formed at an opening of the inner second lug groove 321 with respect to the inner shoulder main groove 21, and raises the bottom of the inner second lug groove 321. Thereby, the rigidity of the inner second land portion 32 is enhanced. Further, the height Hb of the bottom elevated portion 3211 is in the range of 0.30. ltoreq. Hb/Hg 21. ltoreq.0.50 with respect to the groove depth Hg21 of the inner second lug groove 321.

The height Hb of the bottom elevation is determined as: the maximum height from the measurement point of the groove depth Hg21 of the inner second lug groove 321.

The slit 3212 is formed in the bottom elevated portion 3211, and penetrates the bottom elevated portion 3211 in the groove length direction of the inner second lug groove 321. The width (not shown) of the slit 3212 is 1(mm) or less, and the depth (not shown) of the slit 3212 is the height Hb or less of the bottom elevated portion 3211. In the configuration of fig. 5, the depth of the slit 3212 is equal to the height Hb of the bottom elevated portion 3211.

Instead of the inner second sipe 321, a chamfered sipe 321' (see fig. 12) described later may be disposed.

As shown in fig. 3, the inner second sipe 322 extends outward in the tire width direction from the inner central main groove 22, and terminates in the land surface of the inner second land portion 32. Further, a single inner second sipe 322 is disposed between the adjacent inner second sipes 321 and 321. Further, the inner second lateral grooves 321 and the inner second sipes 322 are alternately arranged in the tire circumferential direction. As a result, compared with a configuration in which only the lug grooves or only the sipes are arranged in the tire circumferential direction, the wet performance and the dry performance of the tire can be balanced, and the pattern noise of the tire can be reduced. In particular, the inner second lug groove 321 is disposed at the edge portion of the inner second land portion 32 on the tire contact edge T side, and the inner second sipe 322 is disposed at the edge portion of the inner second land portion 32 on the tire equatorial plane CL side, so that the balance between wet performance and dry performance of the tire can be effectively improved.

Further, the inside second sipe 322 and the inside shoulder sipe 312 of the inside shoulder land portion 31 are inclined in opposite directions to each other with respect to the tire circumferential direction. As a result, compared with a configuration in which both are inclined in the same direction, the edge action in both directions in the tire circumferential direction can be ensured, the wet performance of the tire can be improved, and the pattern noise of the tire can be reduced. Further, the sipe width Wg22 (see FIG. 4) of the inside second sipe 322 is in the range of 0.6 (mm). ltoreq.Wg 22. ltoreq.1.8 (mm), and the sipe depth Hg22 (not shown) is in the range of 3.0 (mm). ltoreq.Hg 22. ltoreq.7.0 (mm). Thus, the inner second sipe 322 is appropriately closed when the tire contacts the ground. Further, the inclination angle θ 22 of the inner second sipe 322 with respect to the tire circumferential direction (see fig. 4) is in the range of 110(deg) ≦ θ 22 ≦ 130 (deg).

Further, in FIG. 3, the extended length L22 of the inner second sipe 322 in the tire width direction and the land width W2 of the inner second land portion 32 preferably have a relationship of 0.15. ltoreq.L 22/W2. ltoreq.0.30, and more preferably have a relationship of 0.20. ltoreq.L 22/W2. ltoreq.0.25. The lower limit ensures the water removal function and the uneven wear suppression function of the inner second sipes 322, and improves the wet performance and uneven wear resistance of the tire, and the upper limit ensures the rigidity of the inner second land portion 32, and ensures the dry performance of the tire.

In particular, in the configuration of fig. 4, the inner second sipe 321 and the inner second sipe 322 are arranged so as not to overlap in the tire width direction. Further, the distance D2 between the inner second lug groove 321 and the inner second sipe 322 in the tire width direction is preferably in the range of 0 (mm). ltoreq.D 2, and more preferably in the range of 2.0 (mm). ltoreq.D 2. As a result, as compared with the structure in which the both are overlapped, the rigidity of the inner second land portion 32 can be ensured, and the dry performance of the tire can be ensured. The upper limit of the distance D2 is not particularly limited, but is limited by the relationship between the extension lengths L21 and L22 (see fig. 3) of the inner second sipe 321 and the inner second sipe 322.

Central ring bank part

Fig. 6 is an enlarged view showing a main portion of a region on the tread surface shown in fig. 2 on the inner side in the vehicle width direction. The figure shows the inboard second land portion 32 and the central land portion 33 particularly enlarged. Fig. 7 is an enlarged view showing the inner second land portion and the central land portion shown in fig. 6. Fig. 8 is a perspective view showing a chamfered portion of the center land portion shown in fig. 6.

As shown in fig. 6, the central land portion 33 includes a plurality of central lug grooves 331 and a plurality of chamfered portions 332.

The central lug groove 331 extends from the inner central main groove 22 toward the tire equatorial plane CL and terminates in the ground contact surface of the central land portion 33. The plurality of central lug grooves 331 are arranged in the tire circumferential direction at a predetermined pitch length P31. In the configuration of fig. 6, the central lug groove 331 has a circular arc shape that is gently curved in the tire circumferential direction, but the configuration is not limited thereto, and the central lug groove 331 may have a linear shape or a curved shape (not shown). The groove width Wg31 (see FIG. 7) of the center lug groove 331 is in the range of 1.5 (mm). ltoreq.Wg 31. ltoreq.4.5 (mm), and the groove depth (not shown) is in the range of 4.5(mm) to 7.0 (mm). The lower limit ensures the drainage function of the center lug 331 to improve the wet performance of the tire, and the upper limit ensures the rigidity of the center land portion 33 to ensure the dry performance of the tire. Further, the inclination angle θ 31 of the center lug groove 331 with respect to the tire circumferential direction (see FIG. 7) is in the range of 110 (deg). ltoreq.θ 31. ltoreq.130 (deg). The occurrence of chipping wear can be suppressed by the lower limit of the inclination angle, and the wet rotation performance of the tire can be ensured by the upper limit.

Further, in FIG. 6, the extended length L31 of the center lug groove 331 in the tire width direction and the ground contact width W3 of the center land portion 33 preferably have a relationship of 0.30. ltoreq.L 31/W3. ltoreq.0.60, and more preferably have a relationship of 0.40. ltoreq.L 31/W3. ltoreq.0.50. The lower limit ensures the drainage function of the center lug 331 to improve the wet performance of the tire, and the upper limit ensures the rigidity of the center land portion 33 to ensure the dry performance of the tire.

In the configuration of fig. 6, the central lug groove 331 and the inner second lug groove 321 of the inner second land portion 32 are inclined in opposite directions with respect to the tire circumferential direction. In this configuration, as compared with a configuration in which both are inclined in the same direction, the edge action in both directions in the tire circumferential direction is ensured, the wet performance of the tire is improved, and the pattern noise of the tire is reduced.

Further, the central lug groove 331 and the inner second sipe 322 of the inner second land portion 32 are inclined in the same direction with respect to the tire circumferential direction. This improves the drainage in the vehicle width direction inner side region.

As shown in fig. 2, the direction of inclination of the zigzag-shaped elongated portion of the outer center main groove 23 with respect to the tire circumferential direction is set to be opposite to the direction of inclination of the inner shoulder lug groove 311 with respect to the tire circumferential direction (see the inclination angle θ 11 in fig. 3). In this configuration, compared to a configuration in which both are inclined in the same direction, the edge action in both directions in the tire circumferential direction can be ensured, and the wet performance of the tire can be improved.

Further, as shown in fig. 6, the central lug groove 331 is arranged to be offset in the tire circumferential direction with respect to an extension line of the inside second sipe 322. In the configuration of fig. 6, all the inside central sipes 331 are arranged offset in the tire circumferential direction with respect to the extension line of the inside second sipes 322, and are arranged offset to the opposite side with respect to the inclination direction of the inside second sipes 322. Further, in FIG. 7, the distance G2 in the tire circumferential direction between the opening position of the inner second sipe 322 with respect to the inner center main groove 22 and the opening position of the center lug groove 331 with respect to the inner center main groove 22 preferably has a relationship of 0. ltoreq.G 2/Wg 31. ltoreq.2.0 with respect to the width Wg31 of the center lug groove 331, more preferably has a relationship of 0.50. ltoreq.G 2/Wg 31. ltoreq.1.50. This reduces pattern noise of the tire.

As shown in fig. 7, the center lug groove 331 does not intersect the tire equatorial plane CL and terminates in the vehicle width direction inner region. Further, the distance D3 in the tire width direction from the tire equatorial plane CL to the termination of the center lug groove 331 is preferably in the range of 1.0 (mm). ltoreq.D 3. Therefore, the wet performance and the pattern noise performance of the tire can be balanced to a higher degree. The upper limit of the distance D3 is not particularly limited, and is restricted by the relationship with the extension length L31 (see fig. 6) of the central lug groove 331.

In fig. 7, the central lug groove 331 includes a bottom raised portion and a slit (reference numeral in the figure is omitted). The configurations of these raised bottom portions and slits are the same as those of the raised bottom portions 3211 and slits 3212 of the inner second lug grooves 321, and therefore, descriptions thereof are omitted.

Instead of the central sipe 331, a chamfered sipe 331' described later may be disposed (see fig. 12).

As shown in fig. 6, the chamfered portion 332 is formed at an edge portion on the vehicle width direction outer side (see fig. 2) of the center land portion 33. In the configuration of fig. 6, the chamfered portion 332 is a triangular pyramid-shaped C-chamfer (see fig. 8) having an L-shape in which a long portion and a short portion are connected to each other on the tread surface of the central land portion 33. Further, the plurality of chamfered portions 332 are continuously formed in the tire circumferential direction. Thus, the edge portion of the central land portion 33 on the outer central main groove 23 side has a zigzag shape in which long portions and short portions are alternately connected. The wet performance of the tire can be improved by the action of the edge portion of the zigzag shape. The ratio of the circumferential length of the short strip portion of the chamfered portion 332 to the circumferential length of the long strip portion (the dimension symbol in the figure is omitted) is preferably in the range of 0.03 to 0.10, and more preferably in the range of 0.04 to 0.06.

Further, in FIG. 6, the pitch length P32 of the zigzag shape of the outer center main groove 23 preferably has a relationship of 0.50. ltoreq. P31/P32. ltoreq.1.00 with respect to the pitch length P31 of the center lug groove 33, more preferably has a relationship of 0.70. ltoreq. P31/P32. ltoreq.0.90. In the configuration of fig. 6, since the plurality of chamfered portions 332 are continuously formed in the tire circumferential direction, the pitch length P32 of the zigzag shape is substantially equal to the circumferential length of the chamfered portion 332. In the configuration of FIG. 6, the pitch length P32 of the zigzag shape is longer than the pitch length P31 of the central lug groove 331 (P31 < P32), and the number N32 of the zigzag shape has a relationship of 1.00. ltoreq.N 32/N31. ltoreq.1.40 with respect to the number N31 of the central lug groove 331.

Further, as shown in fig. 7, the curved portion of the chamfered portion 332 and the terminating portion of the central lug groove 331 are at the same position in the tire circumferential direction. Specifically, as long as the distance D4 in the tire circumferential direction between the curved portion of the chamfered portion 332 and the terminating portion z of the central lug groove 331 is 5.0(mm) or less, it can be said that both are at the same position in the tire circumferential direction. This improves the uneven wear resistance of the tire.

In FIG. 8, the depth Hc of the chamfered portion 332 is in a relationship of 0.30. ltoreq. Hc/Hg 3. ltoreq.0.50 with respect to the groove depth Hg3 of the outer center main groove 23. The improvement of the drainage performance of the chamfered portion 332 can be ensured by the above-described lower limit, and the rigidity of the central land portion 33 can be ensured by the above-described upper limit. Further, the width Wc of the chamfered portion 332 is preferably in the range of 1.0(mm) ≦ Wc ≦ 3.0 (mm). The drainage enhancing action of the chamfered portion 332 can be ensured by the above-described lower limit, and the ground contact area of the central land portion 33 can be ensured by the above-described upper limit.

The depth Hc of the chamfered portion was measured as: distance from the tread of the land portion to the maximum depth position of the chamfered portion.

The width Wc of the chamfered portion is determined as: a distance from a measurement point of the groove width of the main groove to a maximum width position of the chamfered portion.

Outer second land portion

Fig. 9 is an enlarged view showing a main portion of an area on the tread surface shown in fig. 2, the area being located on the outer side in the vehicle width direction. This figure shows the outboard second land portion 34 and the outboard shoulder land portion 35 in particular in enlarged scale. Fig. 10 is an enlarged view showing the outer second land portion and the outer shoulder land portion shown in fig. 9. Fig. 11 is a sectional view in the depth direction of the curved lug groove and the first outer shoulder lug groove shown in fig. 10.

As shown in fig. 9, the outer second land portion 34 includes a plurality of curved traverse grooves 341, a plurality of closed narrow grooves 342, and a plurality of chamfered portions 343.

The curved lug groove 341 extends inward in the tire width direction from the circumferential narrow groove 24, is curved into a hook shape in the tire circumferential direction, and terminates in the ground contact surface of the outer second land portion 34. The curved lug groove 341 has a long-strip structure in the extension portion in the tire width direction and a short-strip structure in the extension portion in the tire circumferential direction. Further, the plurality of curved lug grooves 341 are arranged at a predetermined pitch length in the tire circumferential direction. Further, the curved striated groove 341 has a groove width Wg41 (see FIG. 10) in the range of 1.5 (mm). ltoreq.Wg 41.ltoreq.4.5 (mm), and a groove depth Hg41 (see FIG. 11) has a relationship of 0.50. ltoreq. Hg41/Hg 4. ltoreq.1.50 with respect to the groove depth Hg4 (see FIG. 11) of the circumferential striated groove 24. The drainage function of the curved lug groove 341 can be ensured by the lower limit to improve the wet performance of the tire, and the rigidity of the outer second land portion 34 can be ensured by the upper limit to ensure the dry performance of the tire. The inclination angle θ 41 (see FIG. 10) of the main body portion of the curved lug groove 341 with respect to the tire circumferential direction is in the range of 40 (deg). ltoreq.θ 41.ltoreq.65. The occurrence of chipping wear can be suppressed by the above lower limit, and the wet rotation performance of the tire can be ensured by the above upper limit.

The inclination angle θ 41 of the curved lug groove was measured as: an angle formed between a straight line connecting the end portion of the main body of the curved lug groove and the opening portion of the circumferential narrow groove and the tire circumferential direction.

Further, in FIG. 9, the extended length L41 of the curved lug groove 341 in the tire width direction is in the range of 0.65. ltoreq.L 41/W4. ltoreq.0.85 with respect to the ground contact width W4 of the outer second land portion 34. This improves the dry performance and wet performance of the tire in a well-balanced manner. As shown in fig. 2, the main body portion of the curved lug groove 341 and the inner second lug groove 321 of the inner second land portion 32 are inclined in the same direction with respect to the tire circumferential direction. This enables the wet performance of the tire to be exhibited regardless of the tire rotation direction.

In fig. 10 and 11, the curved groove 341 includes a bottom elevated portion 3411 and a slit 3412. The bottom elevated portions 3411 and the slits 3412 are configured in the same manner as the bottom elevated portions 3211 and the slits 3212 of the inner second striae 321, and therefore, the description thereof will be omitted.

The closed narrow groove 342 is disposed between the adjacent curved cross grooves 341, 341 and extends in the tire circumferential direction. Further, the single closed-end narrow groove 342 is disposed between the adjacent curved cross grooves 341, 341 and is disposed separately from the adjacent curved cross grooves 341, 341. Further, the closed-type narrow groove 342 extends from the terminating portion of the curved lug groove 341 along the extension line of the short bar portion of the curved lug groove 341 in the tire circumferential direction. Further, the closed-end narrow groove 342 has a linear shape, is inclined with respect to the tire circumferential direction, and extends in parallel with a long portion of a chamfered portion 343 described later. This optimizes the arrangement relationship between closed-end narrow groove 342 and curved-cross groove 341, and makes outer second land portion 34 uniform in rigidity.

As shown in fig. 9, the chamfered portion 343 is formed at the edge portion on the tire equatorial plane CL side (see fig. 2) of the outer second land portion 34. Further, the chamfered portion 343 of the outer second land portion 34 has the same configuration as the chamfered portion 332 of the central land portion 33, and is disposed so as to be point-symmetric with respect to the chamfered portion 332 of the central land portion 33. Further, the plurality of chamfered portions 343 are continuously arranged in the tire circumferential direction at the same pitch as the chamfered portions 332 of the central land portion 33, and thus the edge portion of the outer second land portion 34 has a zigzag shape in which long strip portions and short strip portions are alternately connected, and the outer central main groove 23 has a zigzag groove opening portion extending in the tire circumferential direction. The wet performance of the tire can be improved by the action of the edge portion of the zigzag shape.

Outboard tire shoulder land

As shown in fig. 9, the outer shoulder land portion 35 includes a first outer shoulder rib groove 351 and a second outer shoulder rib groove 352.

The first outer shoulder rib groove 351 extends from the tire ground contact edge T inward in the tire width direction, is not connected to the circumferential narrow groove 24, and terminates in the ground contact surface of the outer shoulder land portion 35. The first outer shoulder lug grooves 351 are arranged at a predetermined pitch length in the tire circumferential direction. In the configuration of fig. 9, the first outer shoulder lug groove 351 has an arc shape gently curved in the tire circumferential direction, but the configuration is not limited thereto, and the first outer shoulder lug groove 351 may have a straight shape or a curved shape (not shown). Further, the inclination angle of the first outer shoulder lug groove 351 with respect to the tire circumferential direction (dimension marks in the omitted figure) is in the range of 75(deg) or more and 105(deg) or less. This reduces pattern noise of the tire. As shown in fig. 2, the first outer lug groove 351 and the inner shoulder lug groove 311 of the inner shoulder land portion 31 are inclined in the same direction with respect to the tire circumferential direction. This enables the wet performance of the tire to be exhibited regardless of the tire rotation direction.

The second outer shoulder rib groove 352 extends outward in the tire width direction from the circumferential narrow groove 24, does not intersect the tire ground contact edge T, and terminates in the ground contact surface of the outer shoulder land portion 35. Further, a single second outer shoulder lug groove 352 is disposed between the adjacent first outer shoulder lug grooves 351, 351. Therefore, the first outer shoulder lug grooves 351 and the second outer shoulder lug grooves 352 are alternately arranged in the tire circumferential direction. As a result, compared with a configuration in which only the lug grooves or only the sipes are arranged in the tire circumferential direction, the wet performance and the dry performance of the tire can be balanced, and the pattern noise of the tire can be reduced.

In the configuration of fig. 9, the second outer shoulder lug groove 352 has a straight line shape or a gently curved arc shape, and extends obliquely in parallel to the first outer shoulder lug groove 351. The second outer shoulder rib grooves 352 have a groove width Wg52 (see FIG. 10) of 1.5 (mm). ltoreq.Wg 52. ltoreq.4.5 (mm), and a groove depth Hg52 (see FIG. 11) of 4.0 (mm). ltoreq.Hg 52. ltoreq.7.0 (mm). Thereby, the drainage function of the second outer shoulder lug groove 352 can be ensured. Further, the inclination angle θ 52 (see fig. 10) of the second outer shoulder rib groove 352 with respect to the tire circumferential direction is in the range of 50(deg) ≦ θ 52 ≦ 75 (deg). The inclination angle θ 52 of the second outer shoulder lug 352 is larger than the inclination angle θ 41 of the main body portion of the curved lug 341 (θ 41 < θ 52), and specifically preferably has a relationship of 5 (deg). ltoreq.θ 52- θ 41. ltoreq.10 (deg).

Further, in FIG. 9, the extension L52 of the second outer shoulder lug groove 352 in the tire width direction and the ground contact width W5 of the outer shoulder land portion 35 preferably have a relationship of 0.35. ltoreq.L 52/W5. ltoreq.0.60, more preferably have a relationship of 0.40. ltoreq.L 52/W5. ltoreq.0.55. The lower limit ensures the drainage function of the second outer shoulder rib 352 to improve the wet performance of the tire, and the upper limit ensures the rigidity of the shoulder land portion 31 to ensure the dry performance of the tire.

Further, in FIG. 9, the extension L52 of the second outer shoulder lug 352 in the tire width direction has a relationship of 1.30. ltoreq.L 41/L52. ltoreq.1.80 with respect to the extension L41 of the curved lug 341 of the outer second land portion 34. Therefore, the second outer shoulder rib groove 352 is shorter than the curved rib groove 341. In this configuration, the rigidity of the outer shoulder land portion 35 having a high degree of contribution to the dry performance can be secured while improving the drainage performance of the outer second land portion 34 having a high degree of contribution to the wet performance.

Further, as shown in fig. 9, the second outer shoulder rib 352 is arranged offset in the tire circumferential direction with respect to an extension line of the main body portion of the curved rib 341 of the outer second land portion 34. In the configuration of fig. 9, all the second outer shoulder rib grooves 352 are arranged offset in the tire circumferential direction with respect to the extension line of the curved rib groove 341, and are arranged offset in the same direction from the outside with respect to the inclination direction of the groove center line of the curved rib groove 341. Further, in FIG. 10, the distance G3 in the tire circumferential direction between the position of the opening of the second outer shoulder rib groove 352 relative to the circumferential narrow groove 24 and the position of the opening of the curved rib groove 341 relative to the circumferential narrow groove 24 has preferably a relationship of 2.00. ltoreq.G 3/Wg 52. ltoreq.4.00, more preferably a relationship of 2.50. ltoreq.G 3/Wg 52. ltoreq.3.50, relative to the width Wg52 of the second outer shoulder rib groove 352. This reduces pattern noise of the tire.

As shown in fig. 11, the second outer shoulder rib groove 352 includes: the raised bottom portion 3521 is formed in a groove opening portion corresponding to the circumferential narrow groove 24. This can enhance the rigidity of the shoulder land portion 35. The bottom elevated portion 3521 has the same configuration as the bottom elevated portion 3211 of the inner second lug groove 321, and thus, the description thereof is omitted. However, the bottom elevated portion 3521 of the second outer shoulder rib groove 352 has no slit as compared with the bottom elevated portion 3211 of the inner second rib groove 321.

Further, as shown in fig. 10, the first outer shoulder lug groove 351 and the second outer shoulder lug groove 352 are arranged to overlap each other in the tire width direction. Further, the amount of overlap of the first outer shoulder lug groove 351 and the second outer shoulder lug groove 352 has preferably a relationship of 0.10. ltoreq. D5/W5. ltoreq.0.30, more preferably a relationship of 0.15. ltoreq. D5/W5. ltoreq.0.25, with respect to the ground contact width W5 of the outer shoulder land portion 35. The lower limit ensures the drainage function of the lug grooves 351 and 352 and the wet performance of the tire, and the upper limit ensures the rigidity of the outer shoulder land portion 35 and the dry performance of the tire.

In the configuration of fig. 9, the outer shoulder land portion 35 is a rib continuous in the tire circumferential direction, and is cut in the tire circumferential direction or the tire width direction by a groove or a sipe, whereby the rigidity of the shoulder land portion 35 can be improved.

[ modified examples ]

Fig. 12 is an explanatory view showing a modification of the lug groove shown in fig. 4 and 7. In the figure, the constituent elements described in fig. 4 and 7 are given the same reference numerals, and the description thereof will be omitted.

In the configuration of fig. 2, as shown in fig. 4 and 7, the sipes 312(322) and the lateral grooves 321(331) are open to the main grooves 21(22), respectively, and are disposed so as to face each other with the main grooves 21(22) interposed therebetween. Further, the sipes 312(322) are located on the outer side in the tire width direction with respect to the sipes 321 (331). In this configuration, compared to the configuration in which both are the lug grooves, it is preferable that the rigidity of the land portion 31(32) on the tire ground contact edge T side (see fig. 2) be increased to improve the dry performance of the tire. Further, compared to the configuration in which both are sipes, it is preferable that the land portion 32(33) on the tire equatorial plane CL side (see fig. 2) is provided with the transverse groove 321(331) that opens outward in the tire width direction, so that the wet performance of the tire can be appropriately ensured.

In contrast, in the configuration of fig. 12, a chamfered sipe 321 '(331') is disposed instead of the lug groove 321(331) of fig. 4 and 7. The chamfered sipe 321 '(331') includes: the sipe portion 321 s; and chamfered portions 321c formed along the sipe portion 321 s. The chamfered portion 321c may be formed only at one side edge portion of the sipe portion 321s (see fig. 12), may be formed at both side edge portions of the sipe portion 321s, or may be formed so as to surround the entire circumference of the sipe portion 321s (not shown), and the sipe width of the sipe portion 321s may be in a range of 0.6(mm) to 1.8(mm), and the depth of the sipe portion 321s may be in a range of 3.0(mm) to 7.0 (mm). Thus, the sipe portion 321s is appropriately closed when the tire is grounded.

In this configuration, the rigidity of the land portions 31(32) can be improved as compared with the above-described configurations of fig. 4 and 7, and therefore, the dry performance of the tire can be further improved and the pattern noise of the tire can be reduced. Further, the chamfered portion 321c can ensure a drainage function of the chamfered sipe 321 '(331'), and can ensure the wet performance of the tire.

The chamfered sipe width Wg21(Wg31) was measured as: the total width of the sipe portion and the chamfered portion.

Fig. 13 is an explanatory view showing a modification of the inner second lug groove shown in fig. 4. In this figure, the constituent elements described in fig. 4 are denoted by the same reference numerals, and the description thereof will be omitted.

In the configuration of fig. 4, the opening position of the inside shoulder sipe 312 with respect to the inside shoulder main groove 21 and the opening position of the inside second lug groove 321 with respect to the inside shoulder main groove 21 are significantly offset in the tire circumferential direction.

However, without being limited thereto, the distance G1 in the tire circumferential direction between the opening position of the inside shoulder sipe 312 with respect to the inside shoulder main groove 21 and the opening position of the inside second lug groove 321 with respect to the inside shoulder main groove 21 may have a relationship of 0. ltoreq.G 1/Wg 21. ltoreq.1.00 with respect to the width Wg21 of the inside second lug groove 321. That is, the opening position of the inner second lug groove 321 may be arranged at the same position in the tire circumferential direction with respect to the opening position of the inner shoulder sipe 312.

Fig. 14 is an explanatory view showing a modification of the first outer shoulder lug groove shown in fig. 9. In this figure, the constituent elements described in fig. 4 are denoted by the same reference numerals, and the description thereof will be omitted.

In the configuration of fig. 9, as described above, all the second outer shoulder rib grooves 352 are arranged offset in the tire circumferential direction with respect to the extension line of the curved rib groove 341, and are arranged offset in the same direction with respect to the inclination direction of the groove center line of the curved rib groove 341. Further, the distance G3 in the tire circumferential direction between the position of the second outer shoulder rib groove 352 to the opening of the circumferential narrow groove 24 and the position of the curved rib groove 341 to the opening of the circumferential narrow groove 24 is preferably within the above-described predetermined range. This configuration is preferable in terms of reducing pattern noise of the tire.

In contrast, in the configuration of fig. 14, the plurality of second outer shoulder lug grooves 352a to 352c are arranged so as to be offset in different directions in the tire circumferential direction with respect to the extension lines of the curved lug grooves 341. For example, in the configuration of fig. 14, the second outer shoulder lug groove 352a in the upper part of the drawing is arranged offset upward in the drawing with respect to the extension of the curved lug groove 341, the second outer shoulder lug groove 352b in the middle part of the drawing is arranged on the extension of the curved lug groove 341, and the second outer shoulder lug groove 352c in the lower part of the drawing is arranged offset downward in the drawing with respect to the extension of the curved lug groove 341. In this manner, by disposing the plurality of second outer shoulder lug grooves 352a to 352c so as to be offset in different directions with respect to the extension lines of the curved lug grooves 341, pattern noise can be reduced. Further, in this configuration, the distance G3 in the tire circumferential direction between the position of the second outer shoulder rib groove 352 open to the circumferential narrow groove 24 and the position of the curved rib groove 341 open to the circumferential narrow groove 24 preferably has a relationship of 0. ltoreq.G 3/Wg 52. ltoreq.3.50 with respect to the width Wg52 of the second outer shoulder rib groove 352.

[ Effect ]

As described above, the pneumatic tire 10 includes: an attachment direction display portion (illustration omitted) that displays an attachment direction of the tire with respect to the vehicle; an inner shoulder main groove 21 and an inner center main groove 22 formed in a region on the inner side in the vehicle width direction with respect to the tire equatorial plane CL and extending in the tire circumferential direction; an outer center main groove 23 formed in a region on the outer side in the vehicle width direction and extending in the tire circumferential direction; a circumferential narrow groove 24 formed on the outer side in the tire width direction than the outer center main groove 23 and extending in the tire circumferential direction; and five rows of land portions 31 to 35 (see fig. 2) divided by four grooves 21 to 24. Further, the groove opening portion of the inner shoulder main groove 21 and the groove opening portion of the inner center main groove 22 have linear edge portions, and the groove opening portion of the outer center main groove 23 has an edge portion chamfered in a zigzag shape. Further, the groove width Wg1 of the inner-shoulder main groove 21, the groove width Wg2 of the inner-center main groove 22, and the groove width Wg3 of the outer-center main groove 23 have relationships Wg1< Wg3 and Wg2< Wg 3.

In this configuration, (1) the two main grooves 21, 22 are arranged in the vehicle width direction inner region, and the one main groove 23 and the one circumferential narrow groove 24 are arranged in the vehicle width direction outer region, so that the water drainage performance of the vehicle width direction inner region having a high contribution degree to the wet performance can be ensured, and the rigidity of the vehicle width direction outer region having a high contribution degree to the dry performance can be ensured. Further, (2) since the two main grooves 21, 22 in the vehicle width direction inside region have a straight line shape and the main groove 23 in the vehicle width direction outside region has the chamfered portions 332, 343 (see fig. 6 and 9) having a zigzag shape, the groove volume of the main groove 23 in the vehicle width direction outside region can be relatively enlarged. This ensures the groove volume in the region outside the vehicle width direction, and ensures the wet performance of the tire. Further, (3) the groove width Wg3 of the main groove 23 in the vehicle width direction outer region is larger than the groove widths Wg1 and Wg2 of the two main grooves 21 and 22 in the vehicle width direction inner region, and therefore the groove volume in the vehicle width direction outer region can be secured, and the wet performance of the tire can be secured. This provides an advantage of properly satisfying both wet performance and dry performance of the tire.

Further, in this pneumatic tire 10, the groove widths Wg1, Wg2, and Wg3 have the relationships 0.70. ltoreq. Wg1/Wg 3. ltoreq.0.90 and 0.70. ltoreq. Wg2/Wg 3. ltoreq.0.90. This has the advantage that the relationship among the groove widths Wg1, Wg2, and Wg3 of the main grooves 21 to 23 can be optimized.

Further, in this pneumatic tire 10, the groove widths Wg1, Wg2, and Wg3 have a relationship Wg1< Wg2< Wg 3. This has the advantage that the relationship among the groove widths Wg1, Wg2, and Wg3 of the main grooves 21 to 23 can be optimized.

In the pneumatic tire 10, the groove width Wg4 of the circumferential narrow groove 24 is in the range of 0.10 Wg4/Wg3 to 0.35 with respect to the groove width Wg3 of the outer center main groove 23. This has the advantage that the groove width Wg4 of the circumferential narrow groove 24 can be optimized.

Further, in this pneumatic tire 10, the groove width Wg4 and the groove depth Hg4 of the circumferential narrow groove 24 are in the range of 1.5 (mm). ltoreq.Wg 4. ltoreq.4.0 (mm) and 5.0 (mm). ltoreq.Hg 4. ltoreq.7.5 (mm). This has the advantage that the groove width Wg4 and the groove depth Hg4 of the circumferential narrow groove 24 can be optimized.

Further, in this pneumatic tire 10, the groove width Wg4 and the groove depth Hg4 of the circumferential main grooves 24 are in the range of 3.0 (mm). ltoreq.Wg 4 and 6.7 (mm). ltoreq.Hg 4. This has the advantage that the groove width Wg4 and the groove depth Hg4 of the circumferential narrow groove 24 can be optimized.

Further, in this pneumatic tire 10, the distance Dg1 from the tire equatorial plane CL to the inner shoulder main groove 21, the distance Dg2 from the tire equatorial plane CL to the inner center main groove 22, and the distance Dg3 from the tire equatorial plane CL to the outer center main groove 23 have the relationships of 0.26. ltoreq. Dg 1/TW. ltoreq.0.33, 0.10. ltoreq. Dg 2/TW. ltoreq.0.15, and 0.10. ltoreq. Dg 3/TW. ltoreq.0.15 with respect to the tire ground contact width TW. This has the advantage that the positional relationship of the main grooves 21-23 can be optimized.

In the pneumatic tire 10, the zigzag shape of the outer center main groove 23 is formed by the plurality of chamfered portions 332 and 343 (see fig. 8) formed at the edge portions of the groove opening portions, and the depth Hc of the chamfered portions 332 and 343 is in a relationship of 0.30 Hc/Hg3 0.50 to the groove depth Hg3 of the outer center main groove 23. The lower limit can improve the drainage of the outer center main groove 23, and the upper limit can ensure the rigidity of the center land portion 33.

In addition, in the pneumatic tire 10, the land portion 34 defined by the outer center main groove 23 and the circumferential narrow groove 24 includes: the curved lug groove 341 extends inward in the tire width direction from the circumferential narrow groove 24, is curved into a hook shape in the tire circumferential direction, and terminates inside the land portion 34. This configuration has an advantage that the rigidity of the land portion 34 can be ensured and the drainage in the vehicle width direction outer region can be ensured, as compared with a configuration in which the land portion 34 includes the through-groove.

In addition, in the pneumatic tire 10, the land portion 31 on the outer side in the tire width direction, which is defined by the inner shoulder main groove 21, includes: the inner shoulder lug groove 311 extends inward in the tire width direction from the tire ground contact edge T, terminates in the inner shoulder land portion 31, and is inclined at a predetermined inclination angle with respect to the tire circumferential direction. The zigzag shape of the outer central main groove 23 is formed by alternately connecting long portions and short portions. The inclination direction of the zigzag-shaped long portion with respect to the tire circumferential direction is opposite to the inclination direction of the inner shoulder lug groove 311. In this configuration, compared to a configuration in which both are inclined in the same direction, there is an advantage in that edge actions in both directions in the tire circumferential direction can be ensured, and the wet performance of the tire can be improved.

In addition, in the pneumatic tire 10, the land portion 33 defined by the inner center main groove 22 and the outer center main groove 23 includes: the central lug groove 331 extends from the inner central main groove 22 toward the tire equatorial plane CL side, does not intersect the tire equatorial plane CL, and terminates in the central land portion 33 (see fig. 2). Further, the distance D3 (see FIG. 7) between the end of the center lug groove 331 and the tire equatorial plane CL is in the range of 1.0 (mm). ltoreq.D 3. Therefore, the tire has the advantage of balancing the wet performance and the pattern noise performance of the tire to a higher degree.

In addition, in the pneumatic tire 10, the land portion 34 defined by the inner center main groove 22 and the outer center main groove 23 includes: the plurality of central lug grooves 331 extend from the inner central main groove 22 toward the tire equatorial plane CL and terminate in the central land portion 33 (see fig. 2). Further, the pitch length P32 of the zigzag shape of the outer center main groove 23 has a relationship P31< P32 with respect to the pitch length P31 of the plurality of center lug grooves 331. This has an advantage that pattern noise can be reduced.

In addition, in the pneumatic tire 10, the inner second land portion 32 includes: the inner second sipe 322 extends outward in the tire width direction from the inner main center groove 22, and terminates in the inner second land portion 32, and the center land portion 33 includes: the central lug groove 331 (or the chamfered sipe 331'. refer to fig. 12) extends from the inner central main groove 22 toward the tire equatorial plane CL and terminates in the central land portion 33 (refer to fig. 6). In this configuration, as compared with the configuration in which both are sipes, the water drainage performance of the inner region of the tread in the vehicle width direction can be improved, and the wet performance of the tire can be improved. Further, as compared with the configuration in which both are the lug grooves, the rigidity of the inner region of the tread in the vehicle width direction can be secured, and the dry performance of the tire can be improved. Therefore, the wet performance and the dry performance of the tire can be simultaneously achieved.

Further, in this pneumatic tire 10, all the central lug grooves 331 are arranged so as to be offset in the same direction in the tire circumferential direction with respect to the extension lines of the inside second sipes 322. This has the advantage that the pattern noise of the tire can be reduced.

In the pneumatic tire 10, the land portion 31 on the outer side in the tire width direction defined by the inner shoulder main groove 21 is a rib having a tread surface continuous in the tire circumferential direction (see fig. 3). This has the advantage that the rigidity of the inner shoulder land portion 31 can be ensured, and the dry performance of the tire can be improved.