JP2020100168A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire that can be improved in wet performance and dry performance of the tire.SOLUTION: The pneumatic tire, in which a direction of mounting the tire on a vehicle is specified, has a tread on which an outer second land part 32, a center land part 33 and an inner second land part 34 bulge out partially from a reference contour line of a tread profile to outside in a tire radial direction in a cross sectional view in a tire meridian direction. The outer second land part 32 and the center land part 33 are single ribs not divided in a tire width direction. The inner second land part 34 comprises a circumferential narrow groove 341 dividing in the tire width direction the inner second land part 34.SELECTED DRAWING: Figure 4

Description

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

In recent pneumatic tires, in order to improve the wet performance and dry performance of the tire, the land portion of the tread portion has a tread surface that partially bulges outward in the tire radial direction from the reference contour line of the tread profile. .. As a conventional pneumatic tire adopting such a structure, the technique described in Patent Document 1 is known.

Patent No. 5790876

It is an object of the present invention to provide a pneumatic tire that can improve the wet performance and dry performance of the tire.

In order to achieve the above object, a pneumatic tire according to the present invention has a specification of a mounting direction with respect to a vehicle, and an outer shoulder main groove, an outer center main groove, an inner center main groove and an inner shoulder extending in a tire circumferential direction. A pneumatic tire comprising a main groove and an outer shoulder land portion, an outer second land portion, a center land portion, an inner second land portion, and an outer shoulder land portion which are divided into the main groove, the outer second land portion being provided. The center land portion and the inner second land portion have a tread surface that is partially bulged outward in the tire radial direction from the reference contour line of the tread profile in a sectional view in the tire meridian direction, and the outer second land portion. Is a single rib that is not divided in the tire width direction, and the inner second land portion is provided with a circumferential narrow groove that divides the inner second land portion in the tire width direction.

In the pneumatic tire according to the present invention, in the land portion of the tread center region, the land portions outside the tire equatorial plane in the vehicle width direction (outer second land portion and center land portion) are not divided in the tire width direction. Since it is one rib, there is an advantage that the rigidity of the land portion on the outer side in the vehicle width direction is secured and the steering stability performance of the tire on a dry road surface is secured. On the other hand, the land area on the inside of the tread center area in the vehicle width direction (inner second land area) has a circumferential narrow groove that divides the land area in the tire width direction, improving drainage performance in the tread center area. Therefore, there is an advantage that the wet performance of the tire is improved.

FIG. 1 is a cross-sectional view in the tire meridian direction showing 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. FIG. 3 is an explanatory diagram showing a tread profile of the pneumatic tire shown in FIG. FIG. 4 is an enlarged view showing a tread portion center region of the pneumatic tire shown in FIG. FIG. 5 is a sectional view of the inner second land portion shown in FIG. 4 in the tire meridian direction. FIG. 6 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. FIG. 7 is a table showing the results of performance tests of pneumatic tires according to the embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment. In addition, the constituent elements of this embodiment include those that can be replaced and are obvious, while maintaining the identity of the invention. Further, a plurality of modified examples described in this embodiment can be arbitrarily combined within the scope obvious to those skilled in the art.

[Pneumatic tire]
FIG. 1 is a cross-sectional view in the tire meridian direction showing 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. Further, the same figure shows a radial tire for passenger cars as an example of a pneumatic tire.

In the figure, a cross section in the tire meridian direction is defined as a cross section when the tire is cut along a plane including the tire rotation axis (not shown). The tire equatorial plane CL is defined as a plane that passes through the midpoint of the tire cross-section width measurement point defined by JATMA and is perpendicular to the tire rotation axis. Further, the tire width direction is defined as a direction parallel to the tire rotation axis, and the tire radial direction is defined as 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 directions with respect to the vehicle width direction when the tire is mounted on the vehicle. Further, the left and right regions with the tire equatorial plane as a boundary are respectively defined as a vehicle width direction outer region and a vehicle width direction inner region. Further, the pneumatic tire includes a mounting direction display section (not shown) that indicates the tire mounting direction with respect to the vehicle. The mounting direction display portion is configured by, for example, a mark or unevenness provided on the sidewall portion of the tire. For example, ECER30 (European Economic Commission Regulations Article 30) requires that a vehicle mounting direction display portion be provided on a sidewall portion that is on the outer side in the vehicle width direction when the vehicle is mounted.

The pneumatic tire 1 has an annular structure centered on the tire rotation axis, and has a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, and a tread rubber 15. , A pair of sidewall rubbers 16 and 16 and a pair of rim cushion rubbers 17 and 17 (see FIG. 1).

The pair of bead cores 11, 11 is formed by winding one or a plurality of bead wires made of steel in an annular shape and in multiple layers, and is embedded in the bead portion to form cores for the left and right bead portions. The pair of bead fillers 12, 12 are arranged on the outer circumferences of the pair of bead cores 11, 11 in the tire radial direction to reinforce the bead portion.

The carcass layer 13 has a single-layer structure composed of one carcass ply or a multilayer structure formed by laminating a plurality of carcass plies. The carcass layer 13 is bridged in a toroidal shape between the left and right bead cores 11 to form a tire frame. Make up. Further, both ends of the carcass layer 13 are wound back and locked to the outside in the tire width direction so as to surround the bead core 11 and the bead filler 12. The carcass ply of the carcass layer 13 is formed by coating a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) with a coat rubber and rolling the carcass cord. The cord angle is 100 [deg] or less (defined as the inclination angle in the longitudinal direction of the carcass cord with respect to the tire circumferential direction).

The belt layer 14 is formed by laminating a plurality of belt plies 141 to 143, and is arranged around the outer circumference of the carcass layer 13. The belt plies 141 to 143 include a pair of cross belts 141 and 142 and a belt cover 143.

The pair of intersecting belts 141 and 142 are formed by coating a plurality of belt cords made of steel or organic fiber material with a coating rubber and rolling the cord cords, and have an absolute cord angle of 15 [deg] or more and 55 [deg] or less. Have. The pair of intersecting belts 141 and 142 have cord angles (defined as inclination angles in the longitudinal direction of the belt cord with respect to the tire circumferential direction) of mutually different signs, and the longitudinal directions of the belt cords intersect each other. Stacked (so-called cross-ply structure). Further, the pair of cross belts 141 and 142 are laminated and arranged on the outer side of the carcass layer 13 in the tire radial direction.

The belt cover 143 is formed by coating a belt cover cord made of steel or an organic fiber material with a coat rubber and has a cord angle of 0 [deg] or more and 10 [deg] or less in absolute value. Further, the belt cover 143 is, for example, a strip material formed by coating one or a plurality of belt cover cords with coat rubber, and a plurality of the strip materials are provided in the tire circumferential direction with respect to the outer peripheral surfaces of the cross belts 141 and 142. It is constructed by turning and spirally winding.

The tread rubber 15 is arranged on the tire radial outer periphery of the carcass layer 13 and the belt layer 14 to form a tread portion of the tire. The pair of sidewall rubbers 16 and 16 are respectively arranged on the tire width direction outer side of the carcass layer 13 to form left and right sidewall portions. The pair of rim cushion rubbers 17, 17 extends from the tire radial direction inner side of the rewounding portion of the left and right bead cores 11, 11 and the carcass layer 13 to the tire width direction outer side, and constitutes a rim fitting surface of the bead portion.

[Tread pattern]
FIG. 2 is a plan view showing a tread surface of the pneumatic tire shown in FIG. The figure shows the tread surface of an all-season tire. In the figure, the tire circumferential direction means the direction around the tire rotation axis. Further, the symbol T is the tire ground contact end, and the dimension symbol TW is the tire ground contact width.

As shown in FIG. 2, the pneumatic tire 1 includes a plurality of circumferential main grooves 21 to 24 extending in the tire circumferential direction and a plurality of land portions 31 to partitioned into these circumferential main grooves 21 to 24. 35 and 35 on the tread surface.

The main groove is a groove that is required to display a wear indicator specified by JATMA, and has a groove width of 7.4 [mm] or more and 10.2 [mm] or less and 8.1 [mm] or more and 8.7 [mm]. ] It has the following groove depth. The lug groove described below is a lateral groove extending in the tire width direction and opens when the tire contacts the ground to function as a groove. A sipe described below is a notch formed on the tread surface, and is closed when the tire touches the ground.

The groove width is measured as the distance between the groove walls facing each other in the groove opening in an unloaded state in which the tire is mounted on the specified rim and filled with the specified internal pressure. In the configuration in which the cutout portion or the chamfered portion is formed in the groove opening portion, the groove width is defined as the intersection between the extension line of the tread surface and the extension line of the groove wall in the cross-sectional view in the groove width direction and the groove depth direction. Is measured.

The groove depth is measured as the distance from the tread surface to the groove bottom in an unloaded state in which the tire is mounted on the specified rim and filled with the specified internal pressure. Further, in a configuration in which the groove has a partial uneven portion or sipe on the groove bottom, the groove depth is measured excluding these.

The specified rim means a "standard rim" specified by JATMA, a "Design Rim" specified by TRA, or a "Measuring Rim" specified by ETRTO. Further, the specified internal pressure means the maximum value of "maximum air pressure" specified by JATMA, "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "INFLATION PRESSURES" specified by ETRTO. In addition, the specified load means the maximum value of "maximum load capacity" specified in JATMA, "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or "LOAD CAPACITY" specified in ETRTO. However, in JATMA, in the case of tires for passenger cars, the specified internal pressure is an air pressure of 180 [kPa], and the specified load is 88 [%] of the maximum load capacity at the specified internal pressure.

Further, in the configuration of FIG. 2, the left and right regions having the tire equatorial plane CL as a boundary have two circumferential main grooves 21, 22; 23, 24, respectively. The circumferential main grooves 21 to 24 are arranged symmetrically with the tire equatorial plane CL as the center. In addition, five rows of land portions 31 to 35 are defined by these circumferential main grooves 21 to 24. Further, one land portion 33 is arranged on the tire equatorial plane CL.

However, the present invention is not limited to this, and five or more circumferential main grooves may be arranged, or the circumferential main grooves may be laterally asymmetrical about the tire equatorial plane CL (not shown). Further, the land portion may be arranged at a position off the tire equatorial plane CL by arranging one circumferential main groove on the tire equatorial plane CL (not shown).

A region on the tire equatorial plane CL side is defined as a center region with the left and right outermost circumferential main grooves 21 and 24 as boundaries, and left and right regions on the tire ground contact end T side are defined as shoulder regions.

When the tire shown in FIG. 2 is mounted on a vehicle, the outermost circumferential main groove 21 in the vehicle width direction is defined as the outer shoulder main groove, and the circumferential main groove 22 adjacent to the outer shoulder main groove 21 is defined. It is defined as the outer center groove. Further, the innermost circumferential main groove 24 in the vehicle width direction is defined as an inner shoulder main groove, and the circumferential main groove 23 adjacent to the inner shoulder main groove 24 is defined as an inner center main groove.

In the configuration of FIG. 2, the distances Dg1 and Dg4 from the tire equatorial plane CL to the groove centerlines of the outer and inner shoulder main grooves 21 and 24 are in the range of 26% to 32% of the tire ground contact width TW. It is in. Further, the distance from the tire equatorial plane CL to the groove center lines of the outer and inner center main grooves 22 and 23 is in the range of 8% or more and 12% or less of the tire ground contact width TW.

The groove center line is defined as an imaginary line connecting the midpoints of the distances between the left and right groove walls. If the groove center line of the main groove has a zigzag shape or a wavy shape, the distance to the groove center line should be a straight line passing through the midpoints of the maximum amplitude positions on the left and right of the groove center line and parallel to the tire circumferential direction. Is defined.

The tire ground contact width TW is the contact surface between the tire and the flat plate when the tire is mounted on the specified rim and a specified internal pressure is applied, and the tire is placed perpendicular to the plate in a stationary state and a load corresponding to the specified load is applied. Is measured as the maximum linear distance in the tire axial direction.

The tire ground contact end T is a contact surface between the tire and the flat plate when the tire is mounted on a specified rim and a specified internal pressure is applied, and the tire is placed perpendicular to the plate in a stationary state and a load corresponding to the specified load is applied. Is defined as the maximum width position in the tire axial direction.

In FIG. 2, the land portion 31 on the outer side in the tire width direction defined by the outer shoulder main groove 21 is defined as an outer shoulder land portion, and the land portion 32 on the inner side in the tire width direction is defined as an outer second land portion. The land portion 34 on the outer side in the tire width direction defined by the inner shoulder main groove 24 is defined as an inner shoulder land portion 35, and the land portion 34 on the inner side in the tire width direction is defined as an inner second land portion. Further, the land portion 33 arranged between the outer and inner second land portions 32 and 34 is defined as the center land portion. In a configuration including five or more circumferential main grooves (not shown), two or more rows of center land portions are defined.

[Bulging profile]
FIG. 3 is an explanatory diagram showing a tread profile of the pneumatic tire shown in FIG. This figure exaggerates and shows the bulging treads of the land portions 32 to 34.

As shown in FIG. 3, the tread profile (reference numeral omitted in the figure) is a so-called bulge profile, and the land portions 32 to 34 in the center region of the tread portion are the reference of the tread profile in a sectional view in the tire meridian direction. It has a tread surface that partially bulges outward in the tire radial direction from the contour line Pf.

The tread profile is a contour line of the tread surface in a sectional view in the meridian direction of the tire, and is measured using a laser profiler in an unloaded state in which the tire is mounted on a specified rim and a specified internal pressure is filled. As the laser profiler, for example, a tire profile measuring device (manufactured by Matsuo Co., Ltd.) is used.

The reference contour line of the tread profile is defined as a smooth curve that continuously extends in the ground contact area of the tread portion. Specifically, the reference contour line is defined by a curve formed by combining a plurality of arcs having two to three types of curvature radii, or a continuous function such as an elliptic function, a cycloid function, an involute function, and a power function.

In the above configuration, the land portions 32 to 34 in the tread portion center region have the bulging tread surface, so that the ground contact pressure in the tread portion center region increases. As a result, the ground contact characteristics between the treads of the land portions 32 to 34 and the road surface during traveling on the wet road surface are improved, and the wet performance of the tire is improved.

Further, the swelling amounts G2 to G4 of the swelled treads of the land portions 32 to 34 in the tread portion center region are 0.003≦G2/Wr2 with respect to the widths Wr2 to Wr4 of the land portions 32 to 34, respectively. It has a relationship of ≦0.020, 0.003≦G3/Wr3≦0.020 and 0.003≦G4/Wr4≦0.020. Further, the swelling amount G2 to G4 of the tread is preferably in the range of 0.1 [mm] or more and 0.5 [mm] or less, and in the range of 0.2 [mm] or more and 0.4 [mm] or less. Is more preferable. The above lower limit properly ensures the action of increasing the ground contact pressure of the land portions 32 to 34 by the bulging tread surface. Further, the upper limit suppresses an excessive contact pressure difference between the central portion and the edge portion of the land portions 32 to 34.

The amount of tread bulge is measured as the maximum distance from the reference contour line of the tread profile to the maximum bulge point of the tread on the land.

The width of the land portion is measured as the distance in the tire width direction between the measurement points of the groove widths of the left and right circumferential main grooves that divide the land portion, with the tire mounted on the specified rim and filled with the specified internal pressure in an unloaded state. To be done.

Further, the distance from one edge portion of each land portion 32 to 34 to the maximum bulging position of the tread may be in the range of 40% to 60% with respect to the width Wr2 to Wr4 of each land portion 32 to 34. preferable. Therefore, the maximum bulging position of the tread is arranged at the center of the width of the land portions 32-34.

Further, it is preferable that the bulging amount G2 of the outer second land portion 32 has a relationship of 0.90≦G2/G4≦1.10 with respect to the bulging amount G4 of the inner second land portion 34. Therefore, it is preferable that the swelling amounts G2 and G4 of the left and right second land portions 32 and 34 divided into the outermost circumferential main grooves 21 and 24 are substantially equal.

For example, in the configuration of FIG. 3, all the land portions 32 to 34 in the center area of the tread portion have the swelled tread surface. The treads of the land portions 32 to 34 bulge in an arc shape over the entire width direction of the land portions 32 to 34. The left and right edge portions of the land portions 32 to 34 are on the reference contour line Pf of the tread profile. In the structure in which the cutout portion or the chamfered portion is formed at the edge portion of the land portions 32 to 34, the intersection of the extension line of the tread surface of the land portion and the extension line of the groove wall of the main groove is the edge portion of the land portion. Is defined.

On the other hand, the land portions 31 and 35 in the tread portion shoulder region do not have the bulging tread surface. Specifically, the contour lines of the treads of the outer shoulder land portion 31 and the inner shoulder land portion 35 match the reference contour line Pf of the tread profile. Therefore, the bulging amounts G1 and G5 of the treads of the land portions 31 and 35 are G1=G5=0 [mm]. However, the present invention is not limited to this, and the outer shoulder land portion 31 and the inner shoulder land portion 35 may have a tread surface that bulges from the reference contour line Pf (not shown).

[Groove width of main groove]
In FIG. 3, the groove width Wg1 of the outer shoulder main groove 21, the groove width Wg3 of the inner center main groove 23, and the groove width Wg4 of the inner shoulder main groove 24 have a relationship of Wg3<Wg1<Wg4. Therefore, the groove width Wg3 of the inner center main groove 23 is the narrowest. Further, it is preferable that the groove widths Wg1 and Wg4 have a relationship of 0.01≦(Wg4-Wg1)/Wg3. The groove width ratio Wg1/Wg3 preferably has a relationship of 1.05≦Wg1/Wg3≦1.25, and more preferably 1.05≦Wg1/Wg3≦1.15. Further, the groove width ratio Wg4/Wg3 preferably has a relationship of 1.10≦Wg4/Wg3≦1.30, and more preferably 1.10≦Wg4/Wg3≦1.20.

In the above configuration, since the groove width Wg3 of the inner center main groove 23 is narrow, the rigidity of the land portions 33 and 34 in the inner region in the tire width direction is ensured, and the steering stability performance of the tire on a dry road surface is improved. On the other hand, the groove width Wg4 of the inner shoulder main groove 24 is wide, and the inner second land portion 34 is provided with the circumferential narrow groove 341 described later, whereby the drainage property in the inner region in the tire width direction is secured, and the tire The wet performance of is secured.

Further, the groove width Wg2 of the outer center main groove 22 preferably has a relationship of Wg1<Wg2 with respect to the groove width Wg1 of the outer shoulder main groove 21. Further, it is preferable that the groove widths Wg1, Wg2, Wg3 have a relationship of 0.01≦(Wg2-Wg1)/Wg3. Further, the groove width Wg2 of the outer center main groove 22 preferably has a relationship of 1.05≦Wg2/Wg3 with respect to the groove width Wg3 of the inner center main groove 23, and 1.06≦Wg2/Wg3≦1. More preferably, it has a relationship of 25. In such a configuration, since the groove width Wg2 of the outer center main groove 22 is wider than the groove width Wg3 of the inner center main groove 23 (Wg3<Wg2), as compared with the configuration in which the outer center main groove 22 has a narrow structure, The passing noise of the vehicle is reduced.

In the above configuration, the groove width Wg2 of the outer center main groove 22 is wider than the groove width Wg1 of the outer shoulder main groove 21 at the outermost side in the vehicle width direction (Wg1<Wg2), and the groove of the inner center main groove 23 is larger. Since the width is wider than the width Wg3 (Wg3<Wg2), the passing noise of the vehicle is reduced as compared with the configuration in which the outer center main groove 22 has the narrow structure.

Further, it is preferable that the groove width Wg2 of the outer center main groove 22 has a relationship of Wg4<Wg2 with respect to the groove width Wg4 of the inner shoulder main groove 24. That is, it is most preferable that the groove widths of the four main grooves 21 to 24 have a relationship of Wg3<Wg1<Wg4<Wg2. Therefore, it is preferable that the inner center main groove 23 has the narrowest groove width Wg3 and the outer center main groove 22 has the widest groove width Wg2. Moreover, it is preferable that the groove widths of the four main grooves 21 to 24 are different from each other. However, the present invention is not limited to this, and it suffices that at least the above-described relationships of Wg3<Wg1<Wg4 and Wg3<Wg1<Wg2 are satisfied.

[Land in the tread center area]
FIG. 4 is an enlarged view showing a tread portion center region of the pneumatic tire shown in FIG. FIG. 5 is a sectional view of the inner second land portion shown in FIG. 4 in the tire meridian direction.

As shown in FIG. 4, the outer second land portion 32 is a single rib that is not divided in the tire width direction and has a tread surface that is continuous in the tire circumferential direction. Further, the outer second land portion 32 includes first and second outer second lug grooves 321 and 322.

The first outer second lug groove 321 opens to the outer shoulder main groove 21 at one end and ends in the outer second land portion 32 at the other end. Further, the groove width W21 of the first outer second lug groove 321 is in the range of 1.6 [mm] or more and 3.0 [mm] or less, and the groove depth (dimension symbol omitted in the figure) is 5.9 [mm]. ] And 6.5 [mm] or less. The inclination angle θ21 of the first outer second lug groove 321 with respect to the tire circumferential direction is in the range of 55 [deg] or more and 70 [deg] or less.

The inclination angle of the lug groove is measured as an inclination angle with respect to the tire circumferential direction of a straight line passing through the intersection of the groove center line of the lug groove and both ends of the lug groove in the longitudinal direction.

Further, the distance D21 from the edge portion on the outer side in the tire width direction of the outer side second land portion 32 to the terminal end portion of the first outer side second lug groove 321 is 0.20≦D21/Wr2 with respect to the width Wr2 of the outer side second land portion 32. The relationship <0.50 is preferable, and the relationship 0.25≦D21/Wr2≦0.40 is more preferable.

The distance from the edge portion of the land portion to the end portion of the lug groove is measured as the maximum value of the extension length of the lug groove in the tire width direction.

The second outer second lug groove 322 opens to the outer center main groove 22 at one end and ends in the outer second land portion 32 at the other end. Further, the groove width W42 of the second outer second lug groove 322 is in the range of 1.6 [mm] or more and 3.0 [mm] or less, and the groove depth (the dimension symbol omitted in the drawing) is 5.9 [mm]. ] And 6.5 [mm] or less. The groove width W22 of the second outer second lug groove 322 has a relationship of 0.90≦W22/W21≦1.10 with respect to the groove width W21 of the first outer second lug groove 321. Therefore, the first and second outer second lug grooves 321, 322 have substantially the same groove widths W21, W22.

Further, the inclination angle θ22 of the second outer second lug groove 322 with respect to the tire circumferential direction is in the range of 55 [deg] or more and 70 [deg] or less. Moreover, the inclination angle θ22 of the second outer second lug groove 322 has a relationship of −10 [deg]≦θ22−θ21≦10 [deg] with respect to the inclination angle θ21 of the first outer second lug groove 321. Therefore, the first and second outer second lug grooves 321 and 322 have substantially the same inclination angles θ21 and θ22 and are inclined in the same direction with respect to the tire circumferential direction.

Further, the distance D22 from the edge portion on the tire equatorial plane CL side of the outer second land portion 32 to the terminal end portion of the second outer second lug groove 322 is 0.20≦D22/ with respect to the width Wr2 of the outer second land portion 32. It is preferable to have a relationship of Wr2<0.50, and it is more preferable to have a relationship of 0.25≦D22/Wr2≦0.40. Further, the distance D22 of the second outer second lug groove 322 has a relationship of 0.90≦D22/D21≦1.10 with respect to the distance D21 of the first outer second lug groove 321. Therefore, the first and second outer second lug grooves 321, 322 have substantially the same distances D21, D22.

The center land portion 33 is a single rib that is not divided in the tire width direction and has a tread surface that is continuous in the tire circumferential direction. Further, the center land portion 33 includes a center lug groove 331. Further, the edge portion on the outer side in the vehicle width direction of the center land portion 33 has a plain structure which is not divided into lug grooves or sipes.

The center lug groove 331 opens to the inner center main groove 23 at one end and ends in the center land portion 33 at the other end. Further, the groove width W31 of the center lug groove 331 is in the range of 1.5 [mm] or more and 2.8 [mm] or less, and the groove depth (dimension symbol omitted in the drawing) is 5.9 [mm] or more 6 It is in the range of 0.5 [mm] or less. The inclination angle θ31 of the center lug groove 331 with respect to the tire circumferential direction is in the range of 50 [deg] or more and 70 [deg] or less.

Further, the distance D31 from the edge portion of the center land portion 33 on the inner side in the vehicle width direction to the end portion of the center lug groove 331 is 0.25≦D31/Wr3<0.50 with respect to the width Wr3 of the center land portion 33. It is preferable to have a relationship, and it is more preferable to have a relationship of 0.30≦D31/Wr3≦0.40.

In the above configuration, of the land portions 32 to 34 in the tread center region, the land portions located outside the tire equatorial plane CL in the vehicle width direction (the outer second land portion 32 and the center land portion 33) are divided in the tire width direction. Since it is a single rib which is not provided, the rigidity of the land portions 32 and 33 on the vehicle width direction outer side, which receives a large load when turning on a dry road surface, is secured. This ensures the steering stability of the tire.

The inner second land portion 34 includes a circumferential narrow groove 341, an inner second lug groove 342, and a sipe or narrow groove 343. Further, the edge portion on the outer side in the vehicle width direction of the inner second land portion 34 has a plain structure which is not divided into lug grooves or sipes.

The circumferential narrow groove 341 is a narrow groove extending in the tire circumferential direction, and has a straight shape having a constant groove width in the configuration of FIG. Further, the groove width W41 of the circumferential narrow groove 341 is in the range of 1.0 [mm] or more and 2.0 [mm] or less. The groove width W41 of the circumferential narrow groove preferably has a relationship of 0.03≦W41/Wr4≦0.10 with respect to the width Wr4 of the inner second land portion 34, and 0.04≦W41/Wr4≦. It is more preferable to have a relationship of 0.07.

Further, the groove depth H41 (see FIG. 5) of the circumferential narrow groove 341 is in the range of 3.9 [mm] or more and 4.3 [mm] or less. The groove depth H41 of the circumferential narrow groove 341 has a relationship of 0.40≦H41/Hg4≦0.60 with respect to the groove depth Hg4 of the inner shoulder main groove 24.

Further, in the configuration of FIG. 4, a portion on the tire equatorial plane CL side of the inner second land portion 34 partitioned by the circumferential narrow groove 341 is a thin rib (reference numeral omitted in the drawing) and is continuous in the tire circumferential direction. It has a tread. The left and right edge portions of the thin rib, that is, the edge portion on the side of the center main groove 23 and the edge portion on the side of the circumferential narrow groove 341 have a plain structure having no lug groove or sipe opening. ..

In the above configuration, the land portion on the vehicle width direction inner side in the tread portion center region (inner second land portion 34) is provided with the circumferential narrow groove 341 that divides the land portion 33 in the tire width direction, so that running on a wet road surface At times, the groove area in the inner region in the vehicle width direction that greatly contributes to drainage increases. Thereby, the drainage property of the tread portion center region is improved, and the wet performance of the tire is improved.

Further, the distance D41 from the edge portion on the tire equatorial plane CL side of the inner second land portion 34 to the groove center line of the circumferential narrow groove 341 is 0.20≦D41/Wr4 with respect to the width Wr4 of the inner second land portion 34. It is preferable to have a relationship of ≦0.50, and it is more preferable to have a relationship of 0.25≦D41/Wr4≦0.35. Therefore, the circumferential narrow groove 341 is arranged so as to be biased toward the tire equatorial plane CL side with respect to the center line of the inner second land portion 34.

The inner second lug groove 342 opens to the inner shoulder main groove 24 at one end and ends in the inner second land portion 34 at the other end. Further, the groove width W42 of the inner second lug groove 342 is in the range of 1.7 [mm] or more and 3.4 [mm] or less. Further, the groove width W42 of the inner second lug groove 342 has a relationship of 0.90≦W42/W21≦1.20 with respect to the groove width W21 of the first outer second lug groove 321. Therefore, the first outer second lug groove 321 and the inner second lug groove 342 have substantially the same groove widths W21 and W42.

Further, the groove depth H42 (see FIG. 5) of the inner second lug groove 342 is in the range of 5.9 [mm] or more and 6.5 [mm] or less. Further, the groove depth H42 of the inner second lug groove 342 has a relationship of 1.40≦H42/H41≦1.60 with respect to the groove depth H41 of the circumferential narrow groove 341. Further, the groove depth H42 of the inner second lug groove 342 has a relationship of 0.65≦H42/Hg4≦0.80 with respect to the groove depth Hg4 of the inner shoulder main groove 24. Therefore, the inner second lug groove 342 is deeper than the circumferential narrow groove 341 and shallower than the inner shoulder main groove 24.

The inclination angle θ42 of the inner second lug groove 342 with respect to the tire circumferential direction is in the range of 60 [deg] or more and 80 [deg] or less. Moreover, it is preferable that the inclination angle θ22 of the inner second lug groove 342 has a relationship of 0 [deg]≦θ42−θ21≦20 [deg] with respect to the inclination angle θ21 of the first outer second lug groove 321. It is more preferable to have a relationship of 5 [deg]≦θ42−θ21≦15 [deg]. Further, the inclination angle θ22 of the inner second lug groove 342 is larger than the inclination angle θ21 of the first outer second lug groove 321 (θ21<θ41), and the inclination angle is the same in the tire circumferential direction.

In addition, the distance D42 from the edge portion on the outer side in the tire width direction of the inner second land portion 34 to the end portion of the inner second lug groove 342 is 0.30≦D42/Wr4≦0 with respect to the width Wr4 of the inner second land portion 34. The relationship is preferably 0.50, more preferably 0.30≦D42/Wr4≦0.40. Therefore, the inner second lug groove 342 does not intersect the circumferential narrow groove 341.

Further, it is preferable that the distance D21 of the first outer second lug groove 321 and the distance D42 of the inner second lug groove 342 have a relationship of 1.01≦D42/D21≦1.20, and 1.02≦D42/D21≦. It is more preferable to have the relationship of 1.10. Therefore, the distance D42 of the inner second lug groove 342 is preferably larger than the distance D21 of the first outer second lug groove 321 (D21<D41).

Further, it is preferable that the distance D22 of the second outer second lug groove 322 and the distance D42 of the inner second lug groove 342 have a relationship of 1.01≦D42/D22≦1.20, and 1.02≦D42/D22≦. It is more preferable to have the relationship of 1.10. Therefore, the distance D42 of the inner second lug groove 342 is preferably larger than the distance D22 of the second outer second lug groove 322 (D22<D41).

In the above configuration, since the inner second land portion 34 includes the circumferential narrow groove 341 and the inner shoulder main groove 24, drainage performance in the inner region in the vehicle width direction is improved. Further, since the outer second land portion 32 is provided with the lug grooves 321 and 322 at the left and right edge portions, respectively, the drainage performance in the outer region in the vehicle width direction is improved. Since the lug grooves 321, 322, 342 of the land portions 32, 34 have a closed structure that terminates in the land portions, the rigidity of the land portions 32, 34 is ensured. With these, both wet performance and dry steering stability performance of the tire are compatible.

The sipe or narrow groove 343 connects these grooves 341, 342 by extending from the inner second lug groove 342 and opening to the circumferential narrow groove 341. In the configuration of FIG. 4, the sipe or the narrow groove 343 extends along the extension line of the groove center line of the inner second lug groove 342 and opens to the circumferential narrow groove 341. In such a configuration, the sipe or the narrow groove 343 connects the circumferential narrow groove 341 and the inner second lug groove 342, so that the drainage action from the circumferential narrow groove 341 to the inner second lug groove 342 during tire rolling is effective. Obtained. Thereby, the drainage property in the inner region in the vehicle width direction is improved.

Further, the width W43 of the sipes or the narrow grooves 343 (the dimension symbol is omitted in the drawing) is in the range of 0.4 [mm] or more and 0.8 [mm] or less. The depth H43 (see FIG. 5) of the sipe or the narrow groove 343 has a relationship of 0.90≦H43/H41≦1.10 with respect to the groove depth H41 of the circumferential narrow groove 341. Therefore, the sipes or narrow grooves 343 have the same depth as the circumferential narrow grooves 341.

The sipe width is measured as the maximum opening width of the sipe on the tread tread in an unloaded state in which the tire is mounted on the specified rim and the specified internal pressure is filled.

The sipe depth is measured as the distance from the tread tread to the maximum depth position of the sipe in an unloaded state in which the tire is mounted on the specified rim and the specified internal pressure is filled. Further, in a configuration in which the sipe has a partial uneven portion on the groove bottom, these are excluded and the sipe depth is measured.

In addition, in FIG. 2, lug grooves 322 and 331 that open to the inner edges of the outer second land portion 32 and the center land portion 33 in the vehicle width direction are arranged on an extension line of the lug groove 342 of the inner second land portion 34. .. Thereby, the drainage property of the tread portion center region is enhanced. On the other hand, the lug groove 321 that is open to the edge portion on the outer side in the vehicle width direction of the outer second land portion 32 is offset from the lug groove 322 that is open to the edge portion on the inner side in the vehicle width direction in the tire circumferential direction. .. As a result, the rigidity distribution of the outer second land portion 32 in the tire circumferential direction is made uniform, uneven wear of the land portion is suppressed, and pattern noise due to the arrangement of the lug grooves 321 and 322 is reduced.

However, not limited to this, the lug grooves 322, 331 of the outer second land portion 32 and the center land portion 33 may be arranged offset from the extension line of the lug groove 342 of the inner second land portion 34 (not shown). .. Further, it is preferable that both the lug grooves 322 and 331 are offset in the same direction in the tire circumferential direction with respect to the extension line of the lug groove 342 of the inner second land portion 34.

Further, it is preferable that the width Wr2 of the outer second land portion 32, the width Wr3 of the center land portion 33, and the width Wr4 of the inner second land portion 34 are substantially the same. Specifically, the ratio of the widths Wr2 to Wr4 is preferably in the range of 95% or more and 105% or less. In particular, the width Wr3 of the center land portion 33 is in the range of 95% or more and 105% or less with respect to the width Wr2 of the outer second land portion 32 and the width Wr4 of the inner second land portion 34. As a result, the rigidity of the land portions 32 to 34 in the tread portion center region is made uniform, and the uneven wear resistance and uniformity of the tire are improved.

[Land of shoulder area of tread area]
In FIG. 2, the outer shoulder land portion 31 includes an outer shoulder lug groove 311. The outer shoulder lug groove 311 terminates inside the outer shoulder land portion 31 at one end, and extends in the tire width direction beyond the tire ground contact end T. In addition, the groove width of the outer shoulder lug groove 311 (the dimension symbol omitted in the figure) is in the range of 1.5 [mm] or more and 4.0 [mm] or less, and the groove depth (the dimension symbol omitted in the figure) is It is in the range of 5.9 [mm] or more and 6.5 [mm] or less.

Further, the inner shoulder land portion 35 includes a circumferential narrow groove 351 and an inner shoulder lug groove 352. The circumferential narrow groove 351 is a straight narrow groove extending in the tire circumferential direction, and is arranged biased to the tire equatorial plane CL side with respect to the center line of the ground contact surface of the inner shoulder land portion 35. Further, the circumferential narrow groove 351 has a groove width (dimensions not shown in the drawing) in the range of 1.0 [mm] to 2.0 [mm] and a groove depth (dimensions not shown in the drawing). It is in the range of 3.9 [mm] or more and 4.3 [mm] or less. The inner shoulder lug groove 352 terminates inside the inner shoulder land portion 35 at one end, and extends in the tire width direction beyond the tire ground contact end T. Further, the inner shoulder lug groove 352 has a groove width (dimensions not shown in the figure) in the range of 1.5 [mm] or more and 4.0 [mm] or less, and a groove depth (dimensions not shown in the figure) is It is in the range of 5.9 [mm] or more and 6.5 [mm] or less.

[Modification]
FIG. 6 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. The figure shows a plan view of the vehicle width direction inner region of the tread portion.

In the configuration of FIG. 2, as shown in FIG. 4, the edge portion of the outer shoulder land portion 31 on the outer shoulder main groove 21 side has a plain structure that is not divided into lug grooves or sipes. Such a configuration is preferable in that the rigidity of the outer shoulder land portion 31 is increased and the turning performance of the tire is improved.

On the other hand, in the configuration of FIG. 6, the outer shoulder land portion 31 includes the outer shoulder lug groove 311, the second outer shoulder lug groove 312, and the sipe 313 described above.

The second outer shoulder lug groove 312 is formed at the edge portion on the outer shoulder main groove 21 side, terminates in the outer shoulder land portion 31 at one end, and at the other end, the outer shoulder main groove 21. To open. Further, the first outer shoulder lug grooves 311 and the second outer shoulder lug grooves 312 are alternately arranged in the tire circumferential direction. Further, the second outer shoulder lug groove 312 is arranged on an extension line (not shown) of the groove center line of the first outer second lug groove 321 of the outer second land portion 32. Therefore, the second outer shoulder lug groove 312 is inclined in the same direction as the first outer second lug groove 321.

Further, the groove width W12 of the second outer shoulder lug groove 312 (see FIG. 6) has a relationship of 0.95≦W12/W11≦1.05 with respect to the groove width W11 of the first outer shoulder lug groove 311. It is preferable to have. Further, the groove depth H12 (not shown) of the second outer shoulder lug groove 312 is 0.95≦H12/H11≦1.05 with respect to the groove depth H11 of the first outer shoulder lug groove 311. It is preferable to have Therefore, the first and second shoulder lug grooves 311, 312 have substantially the same groove width and groove depth.

Further, the distance D12 from the edge portion on the outer shoulder main groove 21 side of the outer shoulder land portion 31 to the terminal end portion of the second outer shoulder lug groove 312 is 0.15≦ with respect to the width Wr1 of the outer shoulder land portion 31. It is preferable to have a relationship of D12/Wr1≦0.25, and it is more preferable to have a relationship of 0.18≦D12/Wr1≦0.20. In addition, the first and second shoulder lug grooves 311 and 312 may overlap each other in the tire width direction (see FIG. 6) or may not overlap each other (not shown).

Further, the outer side shoulder land portion 31 includes a sipe 313 extending from the terminal end portion of the second outer side shoulder lug groove 312 in the tire width direction. For example, in the configuration of FIG. 6, the sipe 313 extends along the groove center line of the second outer shoulder lug groove 312 and extends the second outer shoulder lug groove 312. This improves the wet performance of the tire.

[effect]
As described above, the pneumatic tire 1 has the designation of the mounting direction with respect to the vehicle (see FIGS. 1 and 2). Further, the pneumatic tire 1 is divided into an outer shoulder main groove 21, an outer center main groove 22, an inner center main groove 23 and an inner shoulder main groove 24 extending in the tire circumferential direction, and these main grooves 21 to 24. An outer shoulder land portion 31, an outer second land portion 32, a center land portion 33, an inner second land portion 34, and an inner shoulder land portion 35. In addition, the outer second land portion 32, the center land portion 33, and the inner second land portion 34 form a tread surface that partially bulges outward in the tire radial direction from the reference contour line Pf of the tread profile in a sectional view in the tire meridian direction. Have (see FIG. 3). Further, the outer second land portion 32 and the center land portion 33 are a single rib that is not divided in the tire width direction (see FIG. 4 ). Further, the inner second land portion 34 includes a circumferential narrow groove 341 that divides the inner second land portion 34 in the tire width direction.

In such a configuration, (1) the land portions 32 to 34 in the tread portion center region are provided with the swelled treads, whereby the ground contact pressure in the tread portion center region increases. As a result, there is an advantage that the ground contact property between the treads of the land portions 32 to 34 and the road surface during traveling on a wet road surface is improved, and the wet performance of the tire is improved.

(2) Of the land portions 32 to 34 in the center area of the tread portion, the land portions outside the tire equatorial plane CL in the vehicle width direction (the outer second land portion 32 and the center land portion 33) are divided in the tire width direction. Since there is no single rib, the rigidity of the land portions 32 and 33 on the outer side in the vehicle width direction, which receives a large load when turning on a dry road surface, is ensured. Thereby, there is an advantage that the steering stability performance of the tire is secured. In particular, in the configuration in which the land portions 32 and 33 include the bulging tread surface, the ground contact pressure on the tread surface of the land portions 32 and 33 increases as described above. Therefore, since the land portions 32 and 33 have the rib structure, there is an advantage that the steering stability performance of the tire is effectively secured.

On the other hand, (3) the land portion on the inner side in the vehicle width direction of the center region of the tread portion (inner second land portion 34) is provided with the circumferential narrow groove 341 that divides the land portion 33 in the tire width direction. The groove area in the inner region in the vehicle width direction, which greatly contributes to drainage during traveling, increases. Accordingly, there is an advantage that the drainage property of the center region of the tread portion is improved and the wet performance of the tire is improved. In particular, in the configuration in which the land portion 34 includes the bulging tread surface, the ground contact pressure on the tread surface of the land portions 32 and 33 increases as described above. Therefore, the land portion 34 having the circumferential narrow grooves 341 has an advantage that the wet performance of the tire is effectively improved.

In the pneumatic tire 1, the groove width Wg1 of the outer shoulder main groove 21, the groove width Wg3 of the inner center main groove 23, and the groove width Wg4 of the inner shoulder main groove 24 are Wg3<Wg1<Wg4,1. .05≦Wg1/Wg3≦1.25 and 1.10≦Wg4/Wg3≦1.30 (see FIG. 3). In the above configuration, (1) since the groove width Wg3 of the inner center main groove 23 is narrow, the rigidity of the land portions 33, 34 in the inner region in the tire width direction is ensured, and the steering stability performance of the tire on a dry road surface is improved. There is an advantage to improve. On the other hand, (2) since the groove width Wg4 of the inner shoulder main groove 24 is wide and the inner second land portion 34 is provided with the circumferential narrow groove 341, drainage is ensured in the inner region in the tire width direction, There is an advantage that the wet performance of the tire is secured.

In the pneumatic tire 1, the groove width Wg2 of the outer center main groove 22 is Wg1<Wg2 and 0.01≦ with respect to the groove width Wg1 of the outer shoulder main groove 21 and the groove width Wg3 of the inner center main groove 23. It has a relationship of (Wg2-Wg1)/Wg3 (see FIG. 3). In the above configuration, since the groove width Wg2 of the outer center main groove 22 is wider than the groove width Wg1 of the outer shoulder main groove 21 located at the outermost side in the vehicle width direction (Wg1<Wg2), the outer center main groove 22 has a narrow width. There is an advantage that vehicle passing noise is reduced as compared with a structure having a structure.

Further, in this pneumatic tire 1, the distance D41 from the edge portion of the inner second land portion 34 on the tire equatorial plane CL side to the groove center line of the circumferential narrow groove 341 is relative to the width Wr4 of the inner second land portion 34. The relationship is 0.20≦D41/Wr4≦0.50 (see FIG. 4). In such a configuration, since the circumferential narrow groove 341 is arranged biased to the tire equatorial plane CL side with respect to the center line of the inner second land portion 34, the circumferential narrow groove 341 is located on the center line of the land portion having a high ground contact pressure. Compared with the arrangement (not shown), the drainage action of the circumferential narrow groove is improved. Further, as compared with the configuration in which the circumferential narrow groove 341 is arranged on the outer side in the tire width direction from the center line of the inner second land portion 34, the groove of the circumferential narrow groove 341 when an external contact force in the tire width direction acts. There is an advantage that the reduction of the width is suppressed and the drainage action of the circumferential narrow groove 341 is secured.

Further, in this pneumatic tire 1, the groove width W41 of the circumferential narrow groove 341 has a relationship of 0.03≦W41/Wr4≦0.10 with respect to the width Wr4 of the inner second land portion 34 (see FIG. 4). ). With the above lower limit, there is an advantage that the groove width W41 of the circumferential narrow groove 341 is secured and the drainage action of the circumferential narrow groove 341 is secured. In addition, the above upper limit has an advantage of suppressing a decrease in rigidity of the land portion 34 due to the arrangement of the circumferential narrow grooves 341.

Further, in this pneumatic tire 1, the portion of the inner second land portion 34 on the tire equatorial plane CL side defined by the circumferential narrow groove 341 has a thin rib having a tread surface continuous in the tire circumferential direction (reference numeral omitted in the figure). ) (See FIG. 4). In such a configuration, the rigidity of the inner second land portion 34 is properly ensured, as compared with a configuration in which the above-mentioned portion partitioned into the circumferential narrow groove 341 is a block row divided in the tire circumferential direction by a lug groove or a sipe. There are advantages.

Further, in the pneumatic tire 1, the inner second land portion 34 has an inner second lug groove that opens at one end portion to the inner shoulder main groove 24 and ends at the other end portion inside the inner second land portion 34. 342 (see FIG. 4). In addition, the outer second land portion 32 has a first outer second lug groove 321 that opens into the outer shoulder main groove 21 at one end and ends in the outer second land portion 32 at the other end, and A second outer second lug groove 322 having an end opening to the outer center main groove 22 and terminating in the outer second land portion 32 at the other end is provided. In such a configuration, the inner second land portion 34 includes the circumferential narrow groove 341 and the inner shoulder main groove 24, so that the drainage property in the inner region in the vehicle width direction is improved. Further, since the outer second land portion 32 is provided with the lug grooves 321 and 322 at the left and right edge portions, respectively, the drainage performance in the outer region in the vehicle width direction is improved. Since the lug grooves 321, 322, 342 of the land portions 32, 34 have a closed structure that terminates in the land portions, the rigidity of the land portions 32, 34 is ensured. With these, there is an advantage that the wet performance and the dry steering stability performance of the tire are compatible with each other.

Further, in the pneumatic tire 1, the distance D42 from the edge portion on the tire width direction outer side of the inner second land portion 34 to the terminal end portion of the inner second lug groove 342 is 0. The relationship is 30≦D42/Wr4≦0.50 (see FIG. 4). This has an advantage that the extension length of the inner second lug groove 342 is optimized.

Further, in the pneumatic tire 1, the distance D21 from the edge portion on the outer side in the tire width direction of the outer second land portion 32 to the terminal end portion of the first outer second lug groove 321 is relative to the width Wr2 of the outer second land portion 32. It has a relationship of D21/Wr2<0.50 (see FIG. 2). Thereby, there is an advantage that the extension length of the first outer second lug groove 321 is optimized.

Further, in this pneumatic tire 1, the distance D21 of the first outer second lug groove 321 has a relationship of 1.01≦D42/D21≦1.20 with respect to the distance D42 of the inner second lug groove 342 (FIG. 4). reference). In such a configuration, since the extension length of the lug groove 342 in the inner region in the vehicle width direction is larger than the groove length of the lug groove 321 in the outer region, an advantage that the effect of improving the wet performance of the tire can be effectively obtained. There is.

Further, in the pneumatic tire 1, the distance D22 from the edge portion of the outer second land portion 32 on the tire equatorial plane CL side to the terminal end portion of the second outer second lug groove 322 is relative to the width Wr2 of the outer second land portion 32. Have a relationship of D22/Wr2<0.50 (see FIG. 4). As a result, there is an advantage that the extension length of the second outer second lug groove 322 is optimized.

In the pneumatic tire 1, the distance D22 of the second outer second lug groove 322 and the distance D42 of the inner second lug groove 342 have a relationship of 1.01≦D42/D22≦1.20 (see FIG. 4). ). With such a configuration, since the extension length of the lug groove 342 in the inner region in the vehicle width direction is larger than the groove length of the lug groove 322 in the outer region, the advantage of effectively improving the wet performance of the tire can be obtained. There is.

Further, in the pneumatic tire 1, the inner second land portion 34 includes sipes or narrow grooves 343 which extend from the inner second lug grooves 342 and open to the circumferential narrow grooves 341 (see FIG. 4 ). In such a configuration, the sipe or the narrow groove 343 connects the circumferential narrow groove 341 and the inner second lug groove 342, so that the drainage action from the circumferential narrow groove 341 to the inner second lug groove 342 during tire rolling is effective. Obtained. Thereby, there is an advantage that the drainage property in the inner region in the vehicle width direction is improved and the wet performance of the tire is improved.

In addition, in the pneumatic tire 1, the outer shoulder land portion 31 and the inner shoulder land portion 35 do not have the bulging tread surface (see FIG. 3 ). In such a configuration, the land portions 32 to 34 in the tread center region have the bulging tread surface, while the land portions 31, 35 in the tread shoulder region do not have the bulging tread surface, so that the load of the cornering can be improved. The contact pressure difference between the hanging shoulder region and the center region is equalized. This has the advantage of improving dry steering stability during cornering.

Further, in this pneumatic tire 1, the center land portion 33 is provided with a center lug groove 331 which opens at the one end portion to the inner center main groove 23 and ends at the other end portion within the center land portion 33. .. The width Wr3 of the center land portion 33 is in the range of 95% or more and 105% or less with respect to the width Wr2 of the outer second land portion 32 and the width Wr4 of the inner second land portion 34. Thereby, there is an advantage that the rigidity of the land portions 32 to 34 in the tread portion center region is made uniform, and the uneven wear resistance and uniformity of the tire are improved.

FIG. 7 is a table showing the results of performance tests of pneumatic tires according to the embodiment of the present invention.

In this performance test, several types of test tires were evaluated for (1) wet braking performance and (2) dry steering stability performance. A test tire having a tire size of 225/65R17 102H is assembled to a rim having a rim size of 17×6.5J, and an internal pressure of 230 [kPa] and a specified load of JATMA are applied to the test tire. The test tires are mounted on all wheels of a CUV (Crossover Utility Vehicle) of a FF (Front engine Front drive) system with a displacement of 2000 [cc] which is a test vehicle.

(1) In the evaluation regarding wet braking performance, a test vehicle runs on an asphalt road sprinkled with water at a water depth of 1 [mm], and the braking distance from an initial speed of 100 [km/h] is measured. Then, based on the measurement results, index evaluation is performed with the conventional example as a reference (100). The larger the numerical value, the better the evaluation.

(2) In the evaluation regarding the steering stability performance, the test vehicle runs on a test course on a dry road surface having a flat peripheral circuit at 60 [km/h] to 100 [km/h]. Then, the test driver performs a sensory evaluation on the steerability during lane change and cornering and the stability during straight running. This evaluation is performed by index evaluation using the conventional example as a reference (100), and the larger the value, the more preferable.

The test tire of the example has the configuration of FIGS. 1 to 3, the main grooves 21 to 24 have a groove depth of 8.1 [mm], and the narrowest main groove 23 has a groove width Wg3 of 8.2 [mm]. mm]. Further, the land portions 32 to 34 in the tread portion center region have a tread surface that bulges from the reference contour line Pf of the tread profile, and the bulging amounts G2 to G4 are 0.3 [mm]. Further, the outer second land portion 32 has first and second outer second lug grooves 321, 322, the center land portion 33 has a center lug groove 331, and the inner second land portion 34 is a circumferential narrow groove 341, It has an inner second lug groove 342 and a sipe 343. The widths Wr2, Wr3, and Wr4 of the land portions 32 to 34 in the tread portion center region are 23.0 [mm]. The groove depth H41 of the circumferential narrow groove 341 is 4.0 [mm].

The test tire of the conventional example has a tread pattern similar to that of Japanese Patent No. 5790876, and compared with the test tire of Example 1, (1) the outer shoulder lug groove 511 penetrates the outer shoulder land portion 31. Point, (2) the outer second land portion 32 does not have the first outer second lug groove 321, and (3) the inner second land portion 34 does not have the circumferential narrow groove 341 and the sipe 343, And (4) the inner shoulder land portion 35 does not include the circumferential narrow groove 351, which is different.

As the test results show, the test tires of Examples 1 to 20 show improved wet braking performance and dry steering stability performance of the tires.

1 Pneumatic Tire; 11 Bead Core; 12 Bead Filler; 13 Carcass Layer; 14 Belt Layer; 141, 142 Cross Belt; 143 Belt Cover; 15 Tread Rubber; 16 Sidewall Rubber; 17 Rim Cushion Rubber; 21 Outer Shoulder Main Groove; 22 outer center main groove; 23 inner center main groove; 24 inner shoulder main groove; 31 outer shoulder land portion; 311 outer shoulder lug groove; 32 outer second land portion; 321 first outer second lug groove; 322 second outer second lug Groove: 33 Center land portion; 331 Center lug groove; 34 Inner second land portion; 341 Circumferential narrow groove; 342 Inner second lug groove; 343 Sipe or narrow groove; 35 Inner shoulder land portion; 351 Circumferential narrow groove; 352 Inner side Shoulder lug groove

Claims (15)

An outer shoulder main groove, an outer center main groove, an inner center main groove, and an inner shoulder main groove that have a mounting direction specified for a vehicle and extend in the tire circumferential direction, and an outer shoulder land portion that is divided into the main grooves. A pneumatic tire comprising an outer second land portion, a center land portion, an inner second land portion and an outer shoulder land portion,
The outer second land portion, the center land portion and the inner second land portion, in a cross-sectional view in the tire meridian direction, having a tread surface partially bulged outward in the tire radial direction from the reference contour line of the tread profile,
The outer second land portion is a single rib which is not divided in the tire width direction, and
The pneumatic tire, wherein the inner second land portion is provided with a circumferential narrow groove that divides the inner second land portion in the tire width direction. The groove width Wg1 of the outer shoulder main groove, the groove width Wg3 of the inner center main groove, and the groove width Wg4 of the inner shoulder main groove are Wg3<Wg1<Wg4, 1.05≦Wg1/Wg3≦1. 25. The pneumatic tire according to claim 1, having a relationship of 25 and 1.10≦Wg4/Wg3≦1.30. The groove width Wg2 of the outer center main groove is Wg1<Wg2 and 0.01≦(Wg2-Wg1)/Wg3 with respect to the groove width Wg1 of the outer shoulder main groove and the groove width Wg3 of the inner center main groove. The pneumatic tire according to claim 1 or 2, further comprising: The distance D41 from the edge portion on the tire equatorial plane side of the inner second land portion to the groove center line of the circumferential narrow groove is 0.20≦D41/Wr4≦0. with respect to the width Wr4 of the inner second land portion. The pneumatic tire according to any one of claims 1 to 3, which has a relationship of 50. 5. The groove width W41 of the circumferential narrow groove has a relationship of 0.03≦W41/Wr4≦0.10 with respect to the width Wr4 of the inner second land portion. Pneumatic tires. The air according to any one of claims 1 to 5, wherein a portion on the tire equatorial plane side of the inner second land portion partitioned into the circumferential narrow grooves is a thin rib having a tread surface continuous in the tire circumferential direction. Included tires. The inner second land portion has an inner second lug groove that opens at the inner shoulder main groove at one end and ends in the inner second land portion at the other end, and
The outer second land portion has a first outer second lug groove that opens at the outer shoulder main groove at one end and ends in the outer second land portion at the other end, and at one end. The pneumatic tire according to any one of claims 1 to 6, further comprising: a second outer second lug groove that opens to the outer center main groove and ends at the other end in the outer second land portion. The distance D42 from the edge portion on the tire width direction outer side of the inner side second land portion to the end portion of the inner side second lug groove is 0.30≦D42/Wr4≦0.50 with respect to the width Wr4 of the inner side second land portion. The pneumatic tire according to claim 7, having the relationship of The distance D21 from the edge portion on the outer side in the tire width direction of the outer side second land portion to the end portion of the first outer side second lug groove is D21/Wr2<0.50 with respect to the width Wr2 of the outer side second land portion. The pneumatic tire according to claim 7 or 8, further comprising: The pneumatic tire according to claim 9, wherein the distance D21 of the first outer second lug groove and the distance D42 of the inner second lug groove have a relationship of 1.01≦D42/D21≦1.20. The distance D22 from the edge portion on the tire equatorial plane side of the outer second land portion to the end portion of the second outer second lug groove is D22/Wr2<0.50 with respect to the width Wr2 of the outer second land portion. The pneumatic tire according to claim 7, further comprising: The pneumatic tire according to claim 11, wherein the distance D22 of the second outer second lug groove and the distance D42 of the inner second lug groove have a relationship of 1.01≦D42/D22≦1.20. The pneumatic tire according to any one of claims 7 to 12, wherein the inner second land portion is provided with a sipe or a narrow groove extending from the inner second lug groove and opening to the circumferential narrow groove. The pneumatic tire according to any one of claims 1 to 13, wherein the outer shoulder land portion and the inner shoulder land portion do not have the bulging tread surface. The center land portion includes a center lug groove that opens at the inner center main groove at one end and ends at the other end in the center land portion, and
The width of the center land portion is in the range of 95[%] or more and 105[%] or less with respect to the width of the outer second land portion and the width of the inner second land portion. Pneumatic tire described in.

Images