阅读说明：本技术 充气轮胎 (Pneumatic tire ) 是由 水岛春菜 于 2019-01-30 设计创作，主要内容包括：本发明的充气轮胎中,内侧第二陆部(32)具备：倒角部(321),形成于内侧第二陆部(32)的轮胎接地端T侧的边缘部并且在内侧第二陆部(32)的踏面处朝向轮胎周向而扩宽倒角宽度；及横槽(322),在一方的端部处在内侧第二陆部(32)内终止并且在另一方的端部处在倒角部(321)的长度方向的中央部开口。另外,外侧第二陆部(34)及外侧胎肩陆部(35)具备封闭横槽(41),该封闭横槽(41)在一方的端部处在外侧第二陆部(34)内终止,在轮胎宽度方向延伸并贯通周向细槽(24),在另一方的端部处在外侧胎肩陆部(35)的接地面内终止。(In the pneumatic tire of the present invention, the inner second land portion (32) includes: a chamfered portion (321) formed at the edge portion on the tire contact end T side of the inner second land portion (32) and widening the chamfered width toward the tire circumferential direction at the tread surface of the inner second land portion (32); and a lateral groove (322) that terminates inside the inner second land portion (32) at one end and opens at the longitudinal center of the chamfered portion (321) at the other end. The outer second land portion (34) and the outer shoulder land portion (35) are provided with a closed lateral groove (41), and the closed lateral groove (41) terminates at one end in the outer second land portion (34), extends in the tire width direction, penetrates through the circumferential narrow groove (24), and terminates at the other end in the ground contact surface of the outer shoulder land portion (35).)

1. A pneumatic tire having a designation of a mounting direction for a vehicle, comprising: an inner shoulder main groove and an inner center main groove disposed in a vehicle width direction inner region bounded by a tire equatorial plane; an outer central main groove disposed in an outer region in the vehicle width direction; a circumferential narrow groove disposed on the vehicle width direction outer side of the outer center main groove; an inner shoulder land portion and an inner second land portion demarcated by the inner shoulder main groove and the inner center main groove; and an outer second land portion and an outer shoulder land portion partitioned by the outer central main groove and the circumferential narrow groove,

it is characterized in that the preparation method is characterized in that,

the inner second land portion includes: a chamfered portion formed at an edge portion on the tire ground contact end side of the inner second land portion and widening a chamfered width toward the tire circumferential direction at a tread surface of the inner second land portion; and a lateral groove terminating in the inner second land portion at one end and opening at a longitudinal center portion of the chamfered portion at the other end,

the outer second land portion and the outer shoulder land portion include a closed lateral groove that terminates at one end in the outer second land portion, extends in the tire width direction and penetrates through the circumferential narrow groove, and terminates at the other end in a ground contact surface of the outer shoulder land portion.

2. The pneumatic tire as set forth in claim 1,

the maximum width Wc of the chamfered portion has a relationship of 0.05 ≦ Wc/Wr2 ≦ 0.30 with respect to the ground contact width Wr2 of the inner second land portion.

3. The pneumatic tire according to claim 1 or 2,

the maximum length Lc in the tire circumferential direction from the maximum width position to the minimum width position of the chamfered portion is in a relationship of 0.60 Lc/Pc 1.00 with respect to the pitch length Pc of the chamfered portion.

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

the chamfered portion has a triangular shape in which a long side portion and a short side portion are connected to each other at the tread surface of the inner second land portion.

5. The pneumatic tire as set forth in claim 1,

the tire-width-direction extension length D22 of the lateral groove of the inner second land portion has a relationship of 0.20. ltoreq. D22/Wr 2. ltoreq.0.80 with respect to the ground contact width Wr2 of the land portion.

6. The pneumatic tire according to any one of claims 1 to 5,

the maximum groove width W22 of the lateral grooves of the inner second land portion has a relationship of 0.03. ltoreq. W22/Lc. ltoreq.0.10 with respect to the maximum length Lc in the tire circumferential direction from the maximum width position to the minimum width position of the chamfered portion.

7. The pneumatic tire according to any one of claims 1 to 6,

an inclination angle theta 22 of the lateral groove of the inner second land portion with respect to the tire circumferential direction is in a range of 30[ deg ] theta 22 [ deg ] 85[ deg ].

8. The pneumatic tire according to any one of claims 1 to 7,

the distance L22 in the tire circumferential direction from the maximum width position of the chamfered portion to the opening position of the lateral groove with respect to the chamfered portion has a relationship of 0.35. ltoreq.L 22/Lc. ltoreq.0.65 with respect to the maximum length Lc in the tire circumferential direction from the maximum width position to the minimum width position of the chamfered portion.

9. The pneumatic tire according to any one of claims 1 to 8,

a distance Di from the circumferential narrow groove to the outer second land portion-side end portion of the closed lateral groove and a ground contact width Wr4 of the outer second land portion have a relationship of 0.10 or more Di/Wr4 or more and 0.60 or less.

10. The pneumatic tire according to any one of claims 1 to 9,

the distance Do from the circumferential narrow groove to the outer shoulder land portion-side end portion of the closed lateral groove and the ground contact width Wr5 of the shoulder land portion are in a relationship of 0.10. ltoreq. Do/Wr 5. ltoreq.0.60.

11. The pneumatic tire according to any one of claims 1 to 10,

the inclination angle theta of the closed transverse groove relative to the circumferential direction of the tire is within the range of 50 deg to 80 deg.

12. The pneumatic tire according to any one of claims 1 to 11,

the groove width W41 of the closed lateral groove and the groove width Ws of the circumferential narrow groove have a relationship of 0.30-W41/Ws-1.50.

13. The pneumatic tire according to any one of claims 1 to 12,

the left and right edge portions of the outer central main groove have a flat structure without grooves and sipes.

14. The pneumatic tire according to any one of claims 1 to 13,

the inner second land portion includes a narrow groove that opens at an edge portion on the tire equator surface side of the inner second land portion at one end portion and that terminates near or is connected to the maximum width position of the chamfered portion at the other end portion.

15. The pneumatic tire according to any one of claims 1 to 14,

the outer second land portion and the outer shoulder land portion include a plurality of types of the closed lateral grooves having different extending lengths from each other,

the shortest tire width direction extension length L1_ min of the first closed lateral groove and the longest tire width direction extension length L1_ max of the second closed lateral groove have a relationship of 1.10. ltoreq. L1_ max/L1_ min. ltoreq.3.00.

Technical Field

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

Background

In recent years, there is a demand for improvement in the running performance of pneumatic tires not only for the circular traveling but also for the urban area and the highway traveling. Therefore, there is a problem that both dry steering stability performance and wet steering stability performance of the tire should be satisfied. As conventional pneumatic tires related to this problem, there are known techniques described in patent documents 1 to 3.

Disclosure of Invention

Problems to be solved by the invention

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

Means for solving the problems

In order to achieve the above object, a pneumatic tire according to the present invention has a specification of a mounting direction of a vehicle, and includes: an inner shoulder main groove and an inner center main groove disposed in a vehicle width direction inner region bounded by a tire equatorial plane; an outer central main groove disposed in an outer region in the vehicle width direction; a circumferential narrow groove disposed on the vehicle width direction outer side of the outer center main groove; an inner shoulder land portion and an inner second land portion demarcated by the inner shoulder main groove and the inner center main groove; and an outer second land portion and an outer shoulder land portion partitioned by the outer central main groove and the circumferential narrow groove, wherein the inner second land portion includes: a chamfered portion formed at an edge portion on the tire ground contact end side of the inner second land portion and widening a chamfered width toward the tire circumferential direction at a tread surface of the inner second land portion; and a lateral groove that terminates at one end portion in the inner second land portion and opens at the other end portion in a longitudinal center portion of the chamfered portion, wherein the outer second land portion and the outer shoulder land portion include a lateral groove that terminates at one end portion in the outer second land portion, extends in the tire width direction and penetrates through the circumferential narrow groove, and terminates at the other end portion in a ground contact surface of the outer shoulder land portion.

Effects of the invention

According to the pneumatic tire of the present invention, (1) since the inner second land portion includes the chamfered portion and the lateral groove formed at the edge portion on the tire ground contact end side, the drainage property of the inner second land portion is improved, and the wet steering stability performance of the tire is improved. In addition, (2) since the lateral groove of the inner second land portion does not penetrate the land portion, the rigidity of the inner second land portion is ensured, and the dry steering stability performance of the tire is ensured. In addition, (3) since the lateral groove of the inner second land portion is open at the center portion in the longitudinal direction of the chamfered portion, the drainage of the inner second land portion is improved, and the wet steering stability of the tire is improved. In addition, (4) the closed lateral grooves in the outer region in the vehicle width direction penetrate the circumferential narrow grooves, so that drainage near the circumferential narrow grooves is improved, and wet performance of the tire is improved. At the same time, since the closed lateral groove is not open to the circumferential main groove and the tire ground contact end, the rigidity of the left and right land portions partitioned by the circumferential narrow groove is secured. This provides an advantage of efficiently achieving 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 of an embodiment of the present invention.

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

Fig. 3 is an enlarged view showing an area on the vehicle width direction inner side of the pneumatic tire shown in fig. 2.

Fig. 4 is an enlarged plan view showing the inner second land portion shown in fig. 3.

Fig. 5 is a sectional view showing the inner second land portion shown in fig. 3.

Fig. 6 is an explanatory view showing a modification of the lateral groove of the second land portion shown in fig. 4.

Fig. 7 is an enlarged view showing a main portion of an outer region in the vehicle width direction of the pneumatic tire shown in fig. 2.

Fig. 8 is an explanatory view showing a closed lateral groove of the pneumatic tire shown in fig. 7.

Fig. 9 is a graph showing the results of a performance test of the pneumatic tire of the embodiment of the present invention.

Fig. 10 is an explanatory diagram showing a test tire of the conventional example shown in fig. 9.

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 embodiment. The components of the present embodiment include components that can be replaced and are obvious while maintaining the identity of the present invention. The plurality of modifications described in the embodiment can be arbitrarily combined within a range that 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 of an embodiment of the present invention. The figure shows a cross-sectional view of a single-sided region in the radial direction of the tire. In addition, this figure shows a radial tire for a passenger car as an example of a pneumatic tire.

In the figure, the tire meridian cross section is a cross section obtained when the tire is cut on a plane including a tire rotation axis (not shown). Note that reference symbol CL denotes a tire equatorial plane and denotes a plane passing through the center point of the tire in the tire rotation axis direction and perpendicular to the tire rotation axis. The tire width direction is a direction parallel to the tire rotation axis, and the tire radial direction is a direction perpendicular to the tire rotation axis.

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. The 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. The pneumatic tire further includes an assembly direction display unit (not shown) that indicates a tire assembly direction with respect to the vehicle. The mounting direction display unit is configured by, for example, a mark or a projection and recess marked on the sidewall of the tire. For example, ECER30 (article 30 of the european economic commission rule) specifies that a vehicle mounting direction display unit must be provided on a side wall portion that is to be the outer side in the vehicle width direction in a vehicle mounted state.

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

The pair of bead cores 11, 11 are formed by annularly winding multiple turns of 1 or a plurality of bead wires made of steel, and are embedded in the bead portions to form 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 composed of 1 carcass ply or a multi-layer structure formed by laminating a plurality of carcass plies, and is arranged between the left and right bead cores 11, 11 in a ring shape to constitute a tire frame. Both ends of the carcass layer 13 are wound back and locked outward in the tire width direction so as to enclose the bead core 11 and the bead filler 12. The carcass cord 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, or the like) with a coating rubber and rolling the coated 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 ] or more and 90[ deg ] or less in absolute value.

The belt layer 14 is formed by laminating a pair of intersecting belts 141 and 142 and a belt cover 143, and is disposed around 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 coating rubber and rolling the coated cord, and have a belt angle of 20[ deg ] or more and 55[ deg ] or less in absolute value. The pair of cross belts 141 and 142 have belt angles (defined as the inclination angle of the longitudinal direction of the belt cord with respect to the tire circumferential direction) of different signs from each other, and are stacked so that the longitudinal directions of the belt cords cross each other (so-called cross-cord structure). The belt cover 143 is formed by coating a belt cover 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 143 is, for example, a strip material in which 1 or more belt cover cords are covered with a coating rubber, and can be configured by winding the strip material in a spiral shape a plurality of times in the tire circumferential direction with respect to the outer circumferential surface of the intersecting 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 side rubbers 16, 16 are disposed on the outer side in the tire width direction of the carcass layer 13, respectively, to constitute left and right side wall portions. The pair of rim cushion rubbers 17, 17 are disposed on the inner side in the tire radial direction of the turnup 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 illustrated in fig. 1. The figure shows the tread pattern of an all season tire. In the figure, the tire circumferential direction refers to a direction around the tire rotation axis. In addition, reference symbol T is a tire ground contact end, and dimension TW is a tire ground contact width.

As shown in FIG. 2, the pneumatic tire 10 has a tread surface provided with a plurality of circumferential main grooves 21 to 23 and a circumferential narrow groove 24 extending in the tire circumferential direction, and a plurality of land portions 31 to 35 defined by the circumferential grooves 21 to 24.

The main groove is a groove having a display obligation of a wear indicator defined by JATMA, and generally has a groove width of 3.0[ mm ] or more and a groove depth of 6.0[ mm ] or more. The lateral groove described later is a lateral 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 slit formed on the tread surface, and is separated from the lateral groove in the point of closing the sipe when the tire is in contact with the ground.

The circumferential narrow groove 24 will be described later.

The groove width is measured as the maximum value of the distance between the left and right groove walls in the groove opening portion in a no-load state in which the tire is mounted on a predetermined rim and a predetermined internal pressure is applied. In the structure 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 in a cross-sectional view with the groove longitudinal direction as a normal direction. In the structure in which the grooves extend in a zigzag or wavy manner in the tire circumferential direction, the groove width is measured using the center line of the amplitude of the groove wall as a measurement point.

The groove depth is measured as the maximum value of the distance from the tread surface to the groove bottom in a no-load state in which the tire is mounted on a predetermined rim and filled with a predetermined internal pressure. In addition, in the structure in which the groove bottom has local irregularities and sipes, the groove depth was measured by excluding them.

The specified Rim is a "standard Rim" specified by JATMA, a "Design Rim" specified by TRA, or a "Measuring Rim" specified by ETRTO. The predetermined internal pressure is the "maximum air pressure" defined by JATMA, the maximum value of the "time LOAD conditions AT variaous color conditions PRESSURES" defined by TRA, or the "conditions PRESSURES" defined by ETRTO. The predetermined LOAD is a "maximum LOAD CAPACITY" defined by JATMA, a maximum value of "time LOAD conditions AT variatus color requirements" defined by TRA, or "LOAD CAPACITY" defined by ETRTO. In JATMA, the predetermined internal pressure is an air pressure of 180 kPa and the predetermined load is 88 [% ] of the maximum load capacity in the case of a passenger vehicle tire.

For example, in the configuration of fig. 2, the pneumatic tire 10 has a left-right asymmetric tread pattern centered on the tire equatorial plane CL. The vehicle width direction inside region bounded by the tire equatorial plane CL has 2 circumferential main grooves 21, 22, and the vehicle width direction outside region has 1 circumferential main groove 23 and 1 circumferential narrow groove 24. In addition, these circumferential grooves 21, 22; 23. the grooves 24 are arranged symmetrically with respect to the tire equatorial plane CL. Further, these circumferential grooves 21 to 24 define 5 rows of land portions 31 to 35. Further, the 1 land portion 33 is disposed on the tire equatorial plane CL.

The inner-shoulder main groove 21 in the inner region in the vehicle width direction is defined as an inner-shoulder main groove, and the circumferential main groove 22 adjacent to the inner-shoulder main groove 21 is defined as an inner-center main groove. The circumferential main groove 23 in the vehicle width direction outer region is defined as an outer center main groove.

The land portions 31 and 35 on the outer side in the tire width direction defined by the inner shoulder main groove 21 and the circumferential narrow groove 24 are defined as shoulder land portions. The shoulder land portions 31 and 35 are outermost land portions in the tire width direction and are located on the tire ground contact edge T. In addition, the land portions 32, 34 on the tire equatorial plane CL side demarcated by the inner shoulder main groove 21 or the circumferential narrow groove 24 are defined as second land portions. Therefore, the second land portions 32, 34 are adjacent to the shoulder land portions 31, 35 across the inner shoulder main groove 21 or the circumferential narrow groove 24. In addition, the land portion 33 on the tire equatorial plane CL side of the second land portions 32, 34 is defined as a center land portion.

In the configuration of fig. 2, the pneumatic tire 10 includes 3 circumferential main grooves 21 to 23 and a single circumferential narrow groove 24 disposed on the outermost side in the vehicle width direction. However, the pneumatic tire 10 is not limited to this, and may include 4 or more circumferential main grooves and a single circumferential narrow groove 24 (not shown) disposed on the outermost side in the vehicle width direction. In this case, the plurality of central land portions 33 are formed between the inner and outer second land portions 32, 24.

[ vehicle width direction inner side region ]

Fig. 3 is an enlarged view showing an area on the vehicle width direction inner side of the pneumatic tire shown in fig. 2.

In the structure of fig. 2, the vehicle-width-direction inner region bounded by the tire equatorial plane CL includes an inner shoulder main groove 21 and an inner center main groove 22, and an inner shoulder land portion 31, an inner second land portion 32, and a center land portion 33 partitioned by these circumferential main grooves 21, 22.

In addition, the 2 circumferential main grooves 21 and 22 have a straight shape having a constant groove width. The distance Dg1 from the tire equatorial plane CL to the groove center line of the inner shoulder main groove 21 is in the range of 25 [% ] to 40 [% ] with respect to the tire ground contact width TW. The distance Dg2 from the tire equatorial plane CL to the groove center line of the inner center main groove 22 is in the range of 5 [% ] to 20 [% ] with respect to the tire ground contact width TW.

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

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

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

The circumferential main grooves 21, 22 have a groove width in the range of 5.0[ mm ] to 25.0[ mm ], and a groove depth in the range of 5.0[ mm ] to 12.0[ mm ] (dimension numerals are omitted in the drawings).

[ shoulder land portion of inner side tire ]

As shown in fig. 3, the inboard shoulder land portion 31 includes a lateral groove 311 and a narrow groove 312. The lateral groove 311 and the narrow groove 312 do not penetrate the inner shoulder land portion 31 at one end and terminate in the inner shoulder land portion 31, and extend in the tire width direction and intersect the tire ground contact edge T. Therefore, the edge portion of the inboard shoulder land portion 31 on the inboard shoulder main groove 21 side has a flat structure without grooves and sipes, and extends continuously in the tire circumferential direction. Thereby, the noise performance of the tire is improved. The edge portion of the flat structure contributes to dry steering stability and noise performance of the tire, as compared with the edge portion of the opening portion with the groove or sipe.

The distance D11 between the lateral groove 311 and the edge of the narrow groove 312 and the inner shoulder land portion 31 is preferably 0.10. ltoreq.D 11/Wr 1. ltoreq.0.40 with respect to the ground contact width Wr1 of the inner shoulder land portion 31, and more preferably 0.15. ltoreq.D 11/Wr 1. ltoreq.0.30.

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

Further, the ground-contact width Wr1 of the inner-shoulder land portion 31 preferably has a relationship of 0.05. ltoreq. Wr 1/TW. ltoreq.0.30 with respect to the tire ground-contact width TW (refer to FIG. 2).

In the configuration of fig. 3, the lateral groove 311 and the narrow groove 312 have a gentle arc shape curved in the tire circumferential direction. However, the present invention is not limited to this, and the lateral grooves 311 and the narrow grooves 312 may have a linear shape and extend substantially parallel to the tire width direction (not shown). The plurality of lateral grooves 311 and narrow grooves 312 are alternately arranged at a predetermined pitch in the tire circumferential direction. However, the present invention is not limited to this, and the plurality of narrow grooves 312 may be disposed between the adjacent lateral grooves 311, 311 (not shown).

[ second land portion on inner side ]

Fig. 4 and 5 are an enlarged plan view (fig. 4) and a cross-sectional view (fig. 5) showing the inner second land portion shown in fig. 3.

As shown in fig. 3, the inner second land portion 32 includes a chamfered portion 321, a lateral groove 322 having a different groove width, and a narrow groove 323 (first and second lateral grooves).

The chamfered portion 321 is formed at an edge portion of the inner second land portion 32 on the tire ground contact edge T side (i.e., on the inner shoulder main groove 21 side), and connects the tread surface of the inner second land portion 32 and the groove wall surface of the inner shoulder main groove 21 in a flat or curved surface. The chamfered portion 321 has a shape that widens the chamfer width in the tire circumferential direction at the tread surface of the inner second land portion 32. In addition, the plurality of chamfered portions 321 are arranged at predetermined intervals in the tire circumferential direction. The groove volume of the inner shoulder main groove 21 is increased by the chamfered portions 321, and the wet performance of the tire is improved.

In addition, the maximum width Wc of the chamfered portion 321 has preferably a relationship of 0.05. ltoreq. Wc/Wr 2. ltoreq.0.30, more preferably a relationship of 0.15. ltoreq. Wc/Wr 2. ltoreq.0.25 with respect to the ground contact width Wr2 of the inner second land portion 32.

The width of the chamfered portion is measured as the distance in the tire width direction from the edge of the land portion to the ridge of the chamfered portion on the tread surface of the land portion. In addition, the edge of the land portion is defined as an intersection point of an extension line of the groove wall of the circumferential main groove and the tread surface of the land portion. The ridge line of the chamfered portion is defined as a boundary line between the wall surface of the chamfered portion and the tread surface of the land portion.

In addition, the ground contact width Wr2 of the inner second land portion 32 relative to the ground contact width Wr1 of the shoulder land portion 34 preferably has a relationship of 0.50. ltoreq. Wr2/Wr 1. ltoreq.1.50, and more preferably has a relationship of 0.80. ltoreq. Wr2/Wr 1. ltoreq.1.20. Thus, the ground contact widths Wr1, Wr2 of the left and right land portions 31, 32 partitioned by the circumferential main grooves 21, 22 are optimized.

In fig. 4, the maximum length Lc in the tire circumferential direction from the maximum width position 3211 to the minimum width position 3212 of the chamfered portion 321 preferably has a relationship of 0.60 Lc/Pc ≦ 1.00, more preferably 0.80 Lc/Pc ≦ 1.00, with respect to the pitch length Pc (see fig. 3) of the chamfered portion 321. Thereby, the widened region of the chamfer width Wc is appropriately secured. The chamfered portions 321 and 321 adjacent to each other in the tire circumferential direction may be connected to each other or separated from each other on the premise that the above-described condition of the ratio Lc/Pc is satisfied.

In addition, in FIG. 5, the maximum depth Hc of the chamfered portion 321 is preferably in a relationship of 0.20. ltoreq. Hc/Hg 1. ltoreq.0.70 with respect to the maximum depth Hg1 of the circumferential main groove 21, and more preferably in a relationship of 0.30. ltoreq. Hc/Hg 1. ltoreq.0.50.

For example, in the configuration of fig. 4 and 5, the chamfered portion 321 has a triangular taper shape with the minimum width position 3212 as an apex. As shown in fig. 4, the chamfered portion 321 has a triangular shape in which a long side portion (a portion including the reference numerals 3213 and 3214) and a short side portion (the reference numeral is omitted in the drawing) are connected to each other at the tread surface of the inner second land portion 32, and the chamfered width of the chamfered portion 321 gradually increases toward one direction in the tire circumferential direction at the long side portion. As shown in fig. 5, the chamfered portion 321 is a C-chamfer and connects the tread surface of the inner second land portion 32 and the groove wall surface of the inner shoulder main groove 21 in a planar manner. However, the chamfered portion 321 is not limited to this, and may be an R-chamfer connecting the tread surface of the inner second land portion 32 and the groove wall surface of the inner shoulder main groove 21 with a curved surface. The adjacent chamfered portions 321 and 321 are arranged in series without a gap. Thus, the ridge line of the chamfered portion 321 has a zigzag shape extending in the tire circumferential direction along the edge portion of the inner second land portion 32.

The lateral groove 322 is a first lateral groove disposed corresponding to the chamfered portion 321, and as shown in fig. 3, terminates inside the inner second land portion 32 at one end, and opens at the longitudinal center of the chamfered portion 321 at the other end to communicate with the inner shoulder main groove 21.

In this configuration, the lateral grooves 322 communicate with the inner shoulder main grooves 21, so that the drainage performance of the inner second land portion 32 is improved, and the wet handling stability of the tire is improved. In addition, since the lateral groove 322 does not penetrate the inner second land portion 32, the rigidity of the inner second land portion 32 is ensured, and the dry steering stability performance of the tire is ensured. Further, since the lateral grooves 322 are open at the center portion in the longitudinal direction of the chamfered portion 321, the drainage performance of the inner second land portion 32 is improved, and the wet steering stability performance of the tire is improved.

In addition, in FIG. 4, the tire width direction extension D22 of the lateral groove 322 preferably has a relationship of 0.20. ltoreq.D 22/Wr 2. ltoreq.0.80 with respect to the ground contact width Wr2 of the inner second land portion 32, and more preferably has a relationship of 0.40. ltoreq.D 22/Wr 2. ltoreq.0.60. Therefore, the lateral groove 322 preferably terminates at a substantially central portion of the inner second land portion 32.

The extension length of the lateral groove is measured as the distance in the tire width direction from the edge portion on the circumferential main groove side of the land portion to the end portion of the lateral groove.

The maximum groove width W22 of the lateral groove 322 preferably has a relationship of 0.03. ltoreq. W22/Lc. ltoreq.0.10, more preferably 0.04. ltoreq. W22/Lc. ltoreq.0.07, with respect to the maximum length Lc in the tire circumferential direction from the maximum width position 3211 to the minimum width position 3212 of the chamfered portion 321. The maximum groove width W22 of the transverse grooves 322 is preferably in the range of 2.5[ mm ] to W22 to 6.5[ mm ].

The maximum width of the lateral groove is measured as the maximum width of the lateral groove on the tread surface of the land portion. In the case where the lateral groove is a chamfered sipe as described later, the maximum groove width is measured as the maximum width including the chamfered portion.

The inclination angle theta 22 of the lateral groove 322 with respect to the tire circumferential direction is preferably in the range of 30[ deg. ≦ theta 22 ≦ 85[ deg ], and more preferably in the range of 50[ deg. ≦ theta 22 ≦ 70[ deg ].

The inclination angle of the lateral groove is measured as an angle formed between an imaginary line connecting both ends of the lateral groove and the tire circumferential direction.

The distance L22 in the tire circumferential direction from the maximum width position 3211 of the chamfered portion 321 to the opening position of the lateral groove 322 with respect to the chamfered portion 321 preferably has a relationship of 0.35. ltoreq. L22/Lc. ltoreq.0.65, more preferably 0.40. ltoreq. L22/Lc. ltoreq.0.60, with respect to the maximum length Lc in the tire circumferential direction from the maximum width position 3211 to the minimum width position 3212 of the chamfered portion 321. Therefore, the lateral groove 322 is open at the center in the longitudinal direction of the chamfered portion 321.

In FIG. 5, the maximum groove depth H22 of the lateral grooves 322 is preferably in a relationship of 0.40. ltoreq.H 22/Hg 1. ltoreq.0.85, more preferably in a relationship of 0.50. ltoreq.H 22/Hg 1. ltoreq.0.75, with respect to the maximum depth Hg1 of the circumferential direction main grooves 21. As shown in fig. 5, the maximum groove depth H22 of the lateral groove 322 is set to be greater than the maximum depth Hc of the chamfered portion 321.

For example, in the configuration of fig. 4 and 5, the lateral groove 322 has a short linear shape or a gentle arc shape, and opens at the center of the long side portion 3213 of the chamfered portion 321. The number of the transverse grooves 322 and the chamfered portions 321The number of the arrangement is the same, and a single lateral groove 322 opens to 1 chamfered portion 321. Thus, the long side portion 3213 of the chamfered portion 321 is cut off in the tire circumferential direction by the lateral groove 322. In addition, the inclination angle of the lateral groove 322 with respect to the ridge line of the long side portion 3213 of the chamfered portion 321At the position of

The range of (1).

The narrow groove 323 is a second transverse groove disposed corresponding to the chamfered portion 321, and has an edge portion on the tire equatorial plane CL side of the inner second land portion 32 opened at one end portion and terminated near the maximum width position 3211 of the chamfered portion 321 at the other end portion (see fig. 4). However, the narrow groove 323 is not limited to this, and may be connected to the maximum width position 3211 of the chamfered portion 321 (not shown). Further, as long as the end portion of the narrow groove 323 is within a distance of 2.5[ mm ] from the maximum width position 3211 of the chamfered portion 321, the narrow groove 323 can be said to end near the maximum width position 3211 of the chamfered portion 321 or to be connected to the maximum width position 3211 of the chamfered portion 321.

In the above-described configuration, the lateral groove opened in the central portion of the chamfered portion 321 is the wide lateral groove 322, and the lateral groove closed or opened at the maximum width position 3211 of the chamfered portion 321 is the narrow groove 323, so that there are the following advantages. That is, (a) compared with a configuration (not shown) in which all the grooves disposed in the inner second land portion 32 are wide lateral grooves, the rigidity of the inner second land portion 32 is ensured, and the dry performance of the tire is ensured. In addition, (b) compared with a configuration (not shown) in which all the grooves disposed in the inner second land portion 32 are narrow grooves or sipes, the drainage performance of the inner second land portion 32 is improved, and the wet steering stability performance of the tire is improved. Further, (c) compared with a configuration (not shown) in which wide lateral grooves open to the maximum width position of the chamfered portion and narrow grooves or sipes terminate or open at the central portion of the chamfered portion, the rigidity of the inner second land portion 32 at the maximum width position 3211 of the chamfered portion 321 can be ensured while ensuring the drainage action from the lateral grooves 322 to the chamfered portion 321, and therefore the dry handling stability performance and the wet handling stability performance of the tire can be simultaneously achieved.

In FIG. 4, the maximum groove width W23 of the narrow groove 323 is preferably in a relationship of 0< W23/W22. ltoreq.0.80, more preferably in a relationship of 0< W23/W22. ltoreq.0.50, with respect to the maximum groove width W22 of the lateral groove 322. Therefore, the groove width of narrow groove 323 is set sufficiently narrower than the groove width of lateral groove 322.

Further, the maximum groove width W23 of the fine groove 323 is preferably in the range of 0.4[ mm ] W23 [ mm ] or less and 1.5[ mm ], more preferably in the range of 0.5[ mm ] W23 [ mm ] or less and 1.0[ mm ]. Further, the fine groove 323 is preferably a sipe closed at the time of tire ground contact.

The inclination angle θ 23 of the fine groove 323 with respect to the tire circumferential direction is preferably in the range of 30[ deg ] θ 23 ≦ 85[ deg ], and more preferably in the range of 50[ deg ] θ 23 ≦ 70[ deg ].

Further, the maximum groove depth H23 of the fine groove 323 preferably has a relationship of 0.20. ltoreq.H 23/Hg 1. ltoreq.0.70 with respect to the maximum depth Hg1 of the circumferential direction main groove 21, and more preferably has a relationship of 0.40. ltoreq.H 23/Hg 1. ltoreq.0.60. The maximum groove depth H23 of narrow groove 323 is set to be smaller than the maximum groove depth H22 of lateral groove 322.

For example, in the structure of fig. 4 and 5, the fine groove 323 has a short linear shape or a gentle arc shape. The number of the narrow grooves 323 is the same as the number of the chamfered portions 321, and a single narrow groove 323 is disposed to face 1 chamfered portion 321. In addition, the inclination angle of the narrow groove 323 with respect to the ridge line of the long side portion 3213 of the chamfered portion 321At the position of

The range of (1).

As shown in fig. 4, the chamfered portion 321 ends near a maximum width position 3211. Further, the distance Gs between the end portion of the narrow groove 323 and the maximum width position 3211 of the chamfered portion 321 is in the range of Gs.ltoreq.1.5 [ mm ]. This configuration is preferable in the point of "when the tire is vulcanized and molded, a minute gap can be formed between the molding blade of the narrow groove 323 and the molding blade of the chamfered portion 321 in the tire molding die (not shown), and therefore, the vulcanization failure due to air entrapment can be reduced. The lower limit of the distance Gs is not particularly limited, but if it is 0.3[ mm ] or more, the air flow path is ensured, and the above-described vulcanization failure reducing action is ensured.

As shown in fig. 4, only the narrow grooves 323 are open at the edge portion of the inner second land portion 32 on the tire equatorial plane CL side, and the other wide cross grooves are not open. This ensures rigidity of the edge portion of the inner second land portion 32 on the tire equatorial plane CL side, and improves the dry performance of the tire.

[ modified examples ]

Fig. 6 is an explanatory view showing a modification of the lateral groove of the second land portion shown in fig. 4. The figure shows a cross-sectional view of the transverse groove 322 in the groove depth direction.

In the structure of fig. 4, the lateral grooves 322 have a U-shaped cross-sectional shape (not shown), and have a substantially constant groove width from the initial stage to the middle stage of wear. However, the lateral grooves 322 are not limited thereto, and may be chamfered sipes as shown in fig. 6. That is, the lateral groove 322 may be formed of a narrow sipe portion 3221 which is closed when the tire contacts the ground, and a chamfered portion 3222 which is formed in an opening portion of the sipe portion 3221 and widens the groove width W22.

[ Central land portion ]

In fig. 3, the central land portion 33 has a plurality of lateral grooves 331.

The lateral groove 331 terminates in the center land portion 33 at one end, and opens at an edge portion of the center land portion 33 on the vehicle transverse direction inner side at the other end.

Further, the tire width direction extension length D31 of the lateral groove 331 is preferably in a relationship of 0.10. ltoreq.D 31/Wr 3. ltoreq.0.60 with respect to the ground contact width Wr3 of the central land portion 33, and more preferably in a relationship of 0.20. ltoreq.D 31/Wr 3. ltoreq.0.40. Therefore, the lateral groove 331 preferably terminates at a substantially central portion of the central land portion 33.

In addition, the maximum groove width W31 (dimension numerals omitted in the drawing) of the lateral groove 331 of the center land portion 33 is preferably in a relationship of 0.90. ltoreq. W31/W22. ltoreq.1.50, more preferably in a relationship of 0.95. ltoreq. W31/W22. ltoreq.1.05, with respect to the maximum groove width W22 of the lateral groove 322 of the inner second land portion 32. The maximum groove width W31 of the transverse grooves 331 is preferably in the range of 2.5[ mm ] to W31 to 6.5[ mm ].

[ outer region in vehicle width direction ]

In the structure of fig. 2, the vehicle width direction outside region bounded by the tire equatorial plane CL has a single circumferential main groove 23 and a single circumferential narrow groove 24 disposed on the tire width direction outside of the circumferential main groove 23. Further, the circumferential grooves 23 and 24 define an outer shoulder land portion 35 and an outer second land portion 34.

In the configuration of fig. 2, the outer central main groove 23 and the circumferential narrow groove 24 have straight shapes having constant groove widths. The distance Dg3 from the tire equatorial plane CL to the groove center line of the outer center main groove 23 is in the range of 5 [% ] to 20 [% ] with respect to the tire ground contact width TW. The distance Dg4 from the tire equatorial plane CL to the groove center line of the circumferential narrow groove 24 is in the range of 25 [% ] to 40 [% ] with respect to the tire ground contact width TW.

The circumferential narrow groove 24 has a groove width Ws (see fig. 8 described later) in a range of 3.0[ mm ] to 7.0[ mm ], and a groove depth in a range of 3.0[ mm ] to 7.0[ mm ] (dimension numerals are omitted in the figure).

[ closed lateral groove in the outer region in the vehicle width direction ]

Fig. 7 is an enlarged view showing a main portion of an outer region in the vehicle width direction of the pneumatic tire shown in fig. 2. Fig. 8 is an explanatory view showing a closed lateral groove of the pneumatic tire shown in fig. 7. In these drawings, fig. 7 shows the outer second land portion 34 and the outer shoulder land portion 35 in the vehicle width direction outer region, and fig. 8 shows an enlarged view in which the circumferential narrow groove 24 and the plurality of closed lateral grooves 41 are extracted.

As shown in fig. 2, the pneumatic tire 10 includes the above-described circumferential narrow groove 24 and a plurality of closed lateral grooves 41(41A, 41B) in the vehicle width direction outer region.

The closed lateral groove 41 extends in the tire width direction, penetrates the circumferential narrow groove 24, does not open to the circumferential main groove 23 and the tire ground contact edge T, and terminates inside the outer second land portion 34 and the outer shoulder land portion 35. Therefore, the closed lateral grooves 41 branch off in a branch shape in the tire width direction from the circumferential narrow groove 24 and terminate inside the left and right land portions 34, 35. Here, the end portion that closes the inner side in the tire width direction of the lateral groove 41 is simply referred to as "inner end portion", and the end portion that closes the outer side in the tire width direction is simply referred to as "outer end portion". Further, the plurality of closed lateral grooves 41(41A, 41B) are arranged at predetermined intervals in the tire circumferential direction.

As shown in fig. 7, a plurality of types of closed lateral grooves 41(41A, 41B) having different extension lengths are arranged in a mixed manner.

In the above configuration, the closed lateral grooves 41 penetrate the circumferential narrow grooves 24, so that the drainage property near the circumferential narrow grooves 24 is improved, and the wet performance of the tire is improved. At the same time, since the closed lateral groove 41 does not open to the circumferential direction main groove 23 and the tire ground contact edge T, the rigidity of the left and right land portions 34, 35 demarcated by the circumferential direction fine groove 24 is secured. Thus, the wet performance and the dry performance of the tire are efficiently achieved.

Further, since the plurality of kinds of closed lateral grooves 41(41A, 41B) having the extension lengths different from each other are arranged at predetermined intervals in the tire circumferential direction, the terminating portions of the closed lateral grooves 41A, 41B in at least one land portion (the outer second land portion 34 in fig. 7) are inevitably arranged in the tire circumferential direction while being offset from each other in the tire width direction. Therefore, compared to a configuration in which the left and right end portions of the closed lateral groove are aligned with the positions in the tire width direction (not shown), the longer lateral groove portion (the portion on the outer second land portion 34 side of the second closed lateral groove 41B in fig. 7) is disposed on the tread surface of 1 land portion (the outer second land portion 34 in fig. 7), and the wide ground contact region is formed between the adjacent longer lateral groove portions. This improves the wet performance and dry performance of the tire efficiently.

In addition, the extension length L1_ min of the shortest closed lateral groove 41A and the extension length L1_ max of the longest closed lateral groove 41B among the plurality of types of closed lateral grooves 41 preferably have a relationship of 1.10. ltoreq.L 1_ max/L1_ min. ltoreq.3.00, and more preferably have a relationship of 1.20. ltoreq.L 1_ max/L1_ min. ltoreq.1.60. The range of the extension length L1 of the transverse closed groove 41 is not particularly limited, but is limited by the ranges of the distances Di and Do (see fig. 8) of the terminating portions of the transverse closed groove 41 in the land portions 34 and 35, which will be described later.

The extension L1 of the lateral groove is defined as the distance in the tire width direction from the inner end to the outer end of the lateral groove when the tire is mounted on a predetermined rim and a predetermined internal pressure is applied and the tire is set to be in a no-load state. In addition, in the configuration including 3 or more types of closed lateral grooves having different extension lengths from each other, the extension length L1_ min of the shortest first closed lateral groove and the extension length L1_ max of the longest second closed lateral groove were measured.

For example, in the structure of fig. 7, a plurality of closed lateral grooves 41(41A, 41B) are arranged at predetermined intervals in the tire circumferential direction. These closed lateral grooves 41A, 41B intersect only the circumferential narrow groove 24, and are not connected to other grooves or sipes. The outer second land portion 34 and the outer shoulder land portion 35 are not cut by the lateral grooves or sipes in the tire circumferential direction, and have tread surfaces continuous in the tire circumferential direction. The first and second closed lateral grooves 41A and 41B are arranged in parallel to each other by inclining the longitudinal direction thereof in the same direction and at the same inclination angle with respect to the tire circumferential direction. However, the inclination angle θ of the plurality of closed lateral grooves 41A and 41B may be different within a range described later.

In FIG. 7, the ground contact widths Wr4, Wr5 of the outer second land portion 34 and the outer shoulder land portion 35 preferably have a relationship of 1.00. ltoreq. Wr5/Wr 4. ltoreq.2.00, and more preferably have a relationship of 1.10. ltoreq. Wr5/Wr 4. ltoreq.1.50. In addition, the ground contact width Wr4 of the outer second land portion 34 preferably has a relationship of 0. ltoreq. Wr 4/TW. ltoreq.0.30 with respect to the tire ground contact width TW. Thus, the ground contact widths Wr4 and Wr5 of the left and right land portions 34 and 35 defined by the circumferential main groove 23 and the circumferential narrow groove 24 are optimized.

The plurality of closed lateral grooves 41(41A, 41B) are arranged such that at least one of the end portions is offset from each other in the tire width direction. In this case, the terminating portion of the closed lateral groove 41 may be offset on the outer second land portion 34 side (see fig. 7), or may be offset on the outer shoulder land portion 35 side or on both the outer second land portion 34 side and the outer shoulder land portion 35 side (not shown). Further, a plurality of types of closed lateral grooves 41A, 41B having different lengths are arranged in a predetermined order in the tire circumferential direction. In this case, 2 types of closed lateral grooves 41A and 41B may be alternately arranged in the tire circumferential direction (see fig. 7), or 3 or more types of closed lateral grooves 41 may be arranged (not shown).

In fig. 8, the distance Di from the circumferential narrow groove 24 to the inner end of the closed lateral groove 41(41A, 41B) (including the minimum value Di _ min and the maximum value Di _ max in fig. 8) and the ground contact width Wr4 (see fig. 7) of the outer second land portion 34 preferably have a relationship of 0.10. ltoreq. Di/Wr 4. ltoreq.0.80, and more preferably have a relationship of 0.20. ltoreq. Di/Wr 4. ltoreq.0.70. Thereby, the extension length Di in the tire width direction of the closed lateral groove 41 in the outer second land portion 34 is optimized.

In FIG. 8, the distance Do (including the minimum value Do _ min and the maximum value Do _ max in FIG. 8) from the circumferential narrow groove 24 to the outer end of the closing lateral groove 41(41A, 41B) and the ground contact width Wr5 (see FIG. 7) of the outer shoulder land portion 35 preferably have a relationship of 0.10. ltoreq. Do/Wr 5. ltoreq.0.60, and more preferably have a relationship of 0.20. ltoreq. Do/Wr 5. ltoreq.0.40. Thereby, the extension length of the closed lateral groove 41 in the outer shoulder land portion 35 in the tire width direction is optimized.

The distances Di and Do up to the end portions of the lateral grooves are measured as the distances in the tire width direction from the measurement points of the land contact widths Wr4 and Wr5 to the end portions of the lateral grooves when the tire is mounted on a predetermined rim and a predetermined internal pressure is applied and the unloaded state is set. In addition, in a structure in which 3 or more kinds of distances Di, Do having mutually different numerical values are present, the distance Di is required; the maximum Di _ max of Do; do _ max and the minimum Di _ min; do _ min satisfies the above conditions, respectively.

In addition, in FIG. 8, the minimum value Di _ min and the maximum value Di _ max of the distances Di at the inner end portions of the plurality of closed lateral grooves 41(41A, 41B) preferably have a relationship of 1.10. ltoreq. Di _ max/Di _ min. ltoreq.3.00, and more preferably have a relationship of 1.50. ltoreq. Di _ max/Di _ min. ltoreq.2.50. The amount of tire width direction offset Δ Di of the inner end portion of the closed lateral groove 41 is preferably in a relationship of 0.10. ltoreq. Δ Di/Wr 4. ltoreq.0.60, and more preferably in a relationship of 0.20. ltoreq. Δ Di/Wr 4. ltoreq.0.40 with respect to the ground contact width Wr4 (see fig. 7) of the outer second land portion 34. Therefore, in the outer second land portion 34, the terminating portions that close the lateral grooves 41A, 41B are arranged offset in the tire width direction. Accordingly, the positions of the inner end portions of the closed lateral grooves 41A and 41B in the outer second land portion 34 are optimized, and the wet performance and the dry performance of the tire are achieved at the same time. In particular, the outer second land portion 34 greatly contributes to the wet performance, and therefore the wet performance of the tire is efficiently improved by the above-described configuration.

On the other hand, the minimum value Do _ min and the maximum value Do _ max of the distances Do of the outer-side end portions of the plurality of closed lateral grooves 41(41A, 41B) preferably have a relationship of 0.90. ltoreq. Do _ max/Do _ min. ltoreq.1.10, and more preferably have a relationship of 0.95. ltoreq. Do _ max/Do _ min. ltoreq.1.05. The amount of tire width direction offset Δ Do of the outer end portion of the closing lateral groove 41 is preferably in a relationship of 0. ltoreq. Δ Do/Wr 5. ltoreq.0.10, more preferably in a relationship of 0. ltoreq. Δ Do/Wr 5. ltoreq.0.05, with respect to the ground contact width Wr5 (see FIG. 7) of the outer shoulder land portion 35. Therefore, in the outer shoulder land portion 35, the terminating portions of the closing lateral grooves 41A, 41B are aligned in position in the tire width direction. This can ensure the rigidity of the outboard shoulder land portion 35 appropriately, and therefore the dry braking performance of the tire is improved.

An offset amount Δ Di of a termination portion of the lateral groove; Δ Do is a distance Di from the circumferential narrow groove to the terminating portion; the maximum Di _ max of Do; do _ max and the minimum Di _ min; the difference of Do _ min is calculated.

As shown in fig. 8, the plurality of closed lateral grooves 41(41A, 41B) are arranged such that the longitudinal directions thereof are inclined in the same direction with respect to the tire circumferential direction. The inclination angle theta 41 of the closed lateral groove 41 with respect to the tire circumferential direction is preferably in the range of 50[ deg. ≦ theta 41 ≦ 80[ deg ], and more preferably in the range of 60[ deg. ≦ theta 41 ≦ 75[ deg ]. This improves the drainage of the closed lateral grooves 41, and reduces pattern noise of the tire caused by the closed lateral grooves 41.

In addition, the inclination angle θ 41_ min of the minimum-inclined closed lateral groove 41 and the inclination angle θ 41_ max of the maximum-inclined closed lateral groove 41 preferably have a relationship of 0[ deg ] or more and θ 41_ max- θ 41_ min or less and 15[ deg ], and more preferably have a relationship of 0[ deg ] or more and θ 41_ max- θ 41_ min or less and 10[ deg ]. That is, the inclination angle θ 41 of the closed lateral groove 41 is preferably substantially constant. This can ensure the rigidity of the land portion appropriately, and thus prevent uneven wear.

Further, the groove width W41 of the closed lateral groove 41 and the groove width Ws of the circumferential narrow groove 24 preferably have a relationship of 0.30. ltoreq. W41/Ws. ltoreq.1.50, more preferably have a relationship of 0.60. ltoreq. W41/Ws. ltoreq.1.30. This ensures the drainage function of the closed lateral grooves 41.

The groove width W41_ min of the narrowest closed lateral groove 41 and the groove width W41_ max (not shown) of the widest closed lateral groove 41 preferably have a relationship of 1.00. ltoreq.W 41_ max/W41_ min. ltoreq.2.00, and more preferably have a relationship of 1.00. ltoreq.W 41_ max/W41_ min. ltoreq.1.50. That is, the groove width W41_ min of the closed lateral grooves 41 is preferably uniform. This can ensure the rigidity of the land portion appropriately, and thus prevent uneven wear.

For example, in the structure of fig. 8, the closed lateral groove 41 has a straight shape having a constant groove width as a whole, and has a tapered shape in which the groove width is narrowed at its end portion. Further, the left and right end portions of the closed lateral groove 41 narrow the groove width in the same direction in the tire circumferential direction, so that the entire closed lateral groove 41 has a trapezoidal shape having an upper bottom and a lower bottom in the tire circumferential direction. The plurality of closed lateral grooves 41A, 41B are aligned in the tire circumferential direction. However, the present invention is not limited to this, and the end portion of the closed lateral groove 41 may have a rectangular shape or an arc shape (not shown). The entire closed lateral groove 41 may have a rectangular shape or a parallelogram shape (not shown).

In the structure of fig. 7, the edge portions of the central land portion 33 and the outer second land portion 34 on the circumferential main groove 23 side extend continuously in the tire circumferential direction by having a flat structure without sipes and grooves. This improves the noise performance of the tire.

[ shoulder cross groove in the outer region in the vehicle width direction ]

In the configuration of fig. 2, the outer shoulder land portion 35 located in the vehicle width direction outer region includes a plurality of shoulder lateral grooves 42 in the vehicle width direction outer region.

The shoulder lateral groove 42 has one terminating portion in the outer shoulder land portion 35, extends in the tire width direction, and opens to the tire ground contact edge T. The shoulder lateral groove 42 is not communicated with the circumferential narrow groove 24 and the closed lateral groove 41 and does not overlap in the tire width direction. In addition, the plurality of shoulder lateral grooves 42 are arranged at predetermined intervals in the tire circumferential direction.

As shown in fig. 7, the shoulder lateral groove 42 is located on an extension of the groove center line of the long closed lateral groove 41B. In the configuration of fig. 7, the groove center line of the long closed lateral groove 41B has a straight shape, and the groove center line of the shoulder lateral groove 42 has a gentle arc shape. The opening of the shoulder lateral groove 42 in the tire ground contact surface is located on the extension line of the groove center line of the closing lateral groove 41B. This improves the drainage from the outer second land portion 34 to the outer shoulder land portion 35. Further, the short closing lateral groove 41A may be located on an extension line of the groove center line of the shoulder lateral groove 42 (not shown).

As shown in fig. 7, the end portion of the shoulder transverse groove 42 and the outer end portion of the closing transverse groove 41B facing the shoulder transverse groove 42 are separated from each other in the tire width direction. The shoulder lateral groove 42 and the closed lateral groove 41B are not connected by another groove or sipe. The distance D2 in the tire width direction from the end of the shoulder transverse groove 42 to the outer end of the closing transverse groove 41B and the ground contact width Wr5 of the outer shoulder land portion 35 preferably have a relationship of 0.10. ltoreq.D 2/Wr 5. ltoreq.0.70, and more preferably have a relationship of 0.30. ltoreq.D 2/Wr 5. ltoreq.0.60. This can achieve both wet performance and dry performance of the tire. That is, the rigidity and the ground contact area of the outer shoulder land portion 35 are ensured by the lower limit, and the dry performance of the tire is ensured. Further, by the above upper limit, the extending length in the tire width direction of the closed lateral groove 41 and the shoulder lateral groove 42 is secured, and the wet performance of the tire is secured.

In the configuration of fig. 7, the outer shoulder land portion 35 has a flat tread surface that is continuous in the tire circumferential direction without being cut by a groove or a sipe in a region between the end portions of all the shoulder lateral grooves 42 and the outer end portions of all the closing lateral grooves 41(41A, 41B). That is, the shoulder transverse groove 42 and the closure transverse groove 41 do not overlap each other in the tire width direction. This further improves the dry performance of the tire.

In FIG. 7, the arrangement interval P1 between the adjacent closed lateral grooves 41, 41(41A, 41B) in the tire circumferential direction preferably has a relationship of 0.30. ltoreq.P 1/P2. ltoreq.0.70, more preferably 0.40. ltoreq.P 1/P2. ltoreq.0.60, with respect to the arrangement interval P2 between the shoulder lateral grooves 42. Thus, the arrangement intervals P1, P2 of the closing lateral groove 41 and the shoulder lateral groove 42 are optimized. In the structure of fig. 7, a pair of closed lateral grooves 41A, 41B grouped in short and long and 1 shoulder lateral groove 42 are arranged in the tire circumferential direction at a uniform pitch.

The arrangement intervals P1, P2 of the lateral grooves were measured using the intersection points of the groove center lines of the lateral grooves and the groove center lines of the circumferential narrow grooves or the tire ground contact edges as measurement points.

[ Effect ]

As described above, the pneumatic tire 10 has a specification of the mounting direction of the vehicle, and further includes: an inner shoulder main groove 21 and an inner center main groove 22 disposed in a vehicle width direction inner region bounded by a tire equatorial plane CL; an outer center main groove 23 disposed in an outer region in the vehicle width direction; a circumferential narrow groove 24 disposed on the vehicle width direction outer side of the outer center main groove 23; an inner shoulder land portion 31 and an inner second land portion 32 partitioned by the inner shoulder main groove 21 and the inner center main groove 22; and an outer second land portion 34 and an outer shoulder land portion 35 defined by the outer central main groove 23 and the circumferential narrow groove 24 (see fig. 2). Further, the inner second land portion 32 includes: a chamfered portion 321 formed at an edge portion on the tire contact edge T side of the inner second land portion 32 and widening a chamfered width toward the tire circumferential direction at a tread surface of the inner second land portion 32; and a lateral groove 322 terminating in the inner second land portion 32 at one end and opening at the longitudinal center of the chamfered portion 321 at the other end. The outer second land portion 34 and the outer shoulder land portion 35 include a closed lateral groove 41, and the closed lateral groove 41 terminates at one end in the outer second land portion 34, extends in the tire width direction, penetrates the circumferential narrow groove 24, and terminates at the other end in the ground contact surface of the outer shoulder land portion 35.

In this configuration, (1) since the inner second land portion 32 includes the chamfered portion 321 and the lateral groove 322 formed at the edge portion on the tire ground contact edge T side, there is an advantage that the drainage property of the inner second land portion 32 is improved and the wet steering stability performance of the tire is improved. In addition, (2) since the lateral groove 322 of the inner second land portion 32 does not penetrate the land portion 32, there is an advantage that the rigidity of the inner second land portion 32 is ensured and the dry steering stability performance of the tire is ensured. In addition, (3) since the lateral grooves 322 of the inner second land portion 32 are open at the central portion in the longitudinal direction of the chamfered portion 321, there is an advantage that the drainage performance of the inner second land portion 32 is improved and the wet steering stability performance of the tire is improved. In addition, (4) the closed lateral grooves 41 in the vehicle width direction outer region penetrate the circumferential narrow grooves 24, so that the drainage near the circumferential narrow grooves 24 is improved, and the wet performance of the tire is improved. At the same time, since the closed lateral groove 41 does not open to the circumferential direction main groove 23 and the tire ground contact edge T, the rigidity of the left and right land portions 34, 35 demarcated by the circumferential direction fine groove 24 is secured. This provides an advantage of efficiently achieving both wet performance and dry performance of the tire.

In addition, in this pneumatic tire 10, the maximum width Wc of the chamfered portion 321 has a relationship of 0.05 ≦ Wc/Wr2 ≦ 0.30 with respect to the ground contact width Wr2 of the inner second land portion 32 (see fig. 4). The following advantages exist: the chamfered portion 321 ensures the improvement of the drainage performance by the lower limit, and the rigidity of the land portion 32 is ensured by the upper limit.

In the pneumatic tire 10, the maximum length Lc (see fig. 4) in the tire circumferential direction from the maximum width position 3211 to the minimum width position 3212 of the chamfered portion 321 has a relationship of 0.60 ≦ Lc/Pc ≦ 1.00 with respect to the pitch length Pc (see fig. 3) of the chamfered portion 321. The following advantages exist: the effect of the chamfered portion 321 on improving the drainage is ensured by the lower limit, and the planar shape of the chamfered portion 321 is optimized by the upper limit.

In addition, in the pneumatic tire 10, the chamfered portion 321 has a triangular shape in which a long side portion and a short side portion are connected to each other at the tread surface of the inner second land portion 32 (see fig. 4). This has the advantage that the drainage effect of the chamfered portion 321 is improved.

In addition, in this pneumatic tire 10, the tire width direction extension length D22 of the lateral groove 322 of the inner second land portion 32 has a relationship of 0.20 ≦ D22/Wr2 ≦ 0.80 with respect to the ground contact width Wr2 of the inner second land portion 32 (see fig. 4). The following advantages exist: the horizontal groove 322 is ensured to improve the drainage performance by the lower limit, and the rigidity of the inner second land portion 32 is ensured by the upper limit.

In the pneumatic tire 10, the maximum groove width W22 of the lateral groove 322 of the inner second land portion 32 has a relationship of 0.03 ≦ W22/Lc ≦ 0.10 for the maximum length Lc in the tire circumferential direction from the maximum width position 3211 to the minimum width position 3212 of the chamfered portion 321 (see fig. 4). The following advantages exist: the horizontal groove 322 is ensured to improve the drainage performance by the lower limit, and the rigidity of the inner second land portion 32 is ensured by the upper limit.

In addition, in this pneumatic tire 10, the inclination angle θ 22 of the lateral groove 322 of the inner second land portion 32 with respect to the tire circumferential direction is in the range of 30[ deg. ≦ θ 22 ≦ 85[ deg ] (see fig. 4). This has the advantage that the inclination angle θ 22 of the lateral groove 322 is optimized.

In the pneumatic tire 10, the distance L22 in the tire circumferential direction from the maximum width position 3211 of the chamfered portion 321 to the opening position of the lateral groove 322 with respect to the chamfered portion 321 has a relationship of 0.35 ≦ L22/Lc ≦ 0.65 with respect to the maximum length Lc in the tire circumferential direction from the maximum width position 3211 to the minimum width position 3212 of the chamfered portion 321 (see fig. 4). In this configuration, since the lateral groove 322 is open at the center in the longitudinal direction of the chamfered portion 321, there is an advantage that the drainage effect of the combination of the lateral groove 322 and the chamfered portion 321 is further improved.

In the pneumatic tire 10, the distance Di from the circumferential narrow groove 24 to the end portion on the outer second land portion 34 side of the closed lateral groove 41 (including the minimum value Di _ min and the maximum value Di _ max of the distance Di in fig. 8) and the ground contact width Wr4 (see fig. 7) of the outer second land portion 34 have a relationship of 0.10 or more and Di/Wr4 or more and 0.80 or less. This has the advantage that the extension Di of the closed lateral groove 41 in the outer second land portion 34 in the tire width direction is optimized. That is, the extension Di of the closed lateral grooves 41 in the outer second land portion 34 is ensured by the lower limit, and the effect of the closed lateral grooves 41 on improving the wet performance is ensured. Further, due to the above upper limit, a decrease in rigidity of the outer second land portion 34 caused by an excessively large extension Di of the closed lateral groove 41 is suppressed.

In the pneumatic tire 10, the distance Do from the circumferential narrow groove 24 to the end portion on the outer shoulder land portion 35 side of the closing lateral groove 41 (including the minimum value Do _ min and the maximum value Do _ max of the distance Do in fig. 8) and the ground contact width Wr5 (see fig. 7) of the outer shoulder land portion 35 have a relationship of 0.10 to Do/Wr5 to 0.60. This has the advantage that the extension of the closed lateral groove 41 in the outboard shoulder land portion 35 in the tire width direction is optimized. That is, the extension Do of the closed lateral groove 41 in the outboard shoulder land portion 35 is ensured by the lower limit, and the effect of the closed lateral groove 41 on improving the wet performance is ensured. Further, by the above upper limit, the decrease in rigidity of the outer shoulder land portion 35 caused by the excessively large extension Do of the closing lateral groove 41 is suppressed.

In the pneumatic tire 10, the inclination angle θ of the closed lateral grooves 41 with respect to the tire circumferential direction is in the range of 55[ deg ] to θ [ deg ] (see fig. 8). This has the advantage of improving the drainage of the closed lateral grooves 41, and also has the advantage of reducing the pattern noise of the tire caused by the closed lateral grooves 41.

In addition, in the pneumatic tire 10, the groove width W41 of the closed lateral groove 41 and the groove width Ws of the circumferential narrow groove 24 have a relationship of 0.30. ltoreq. W41/Ws. ltoreq.1.50. This has the advantage that the drainage function of the closed lateral grooves 41 is appropriately ensured.

In the pneumatic tire 10, the left and right edge portions of the outer center main groove 23 have a flat structure without grooves and sipe openings (see fig. 2). In this structure, since the outer center main groove 23 has an edge portion having a flat structure, there is an advantage that the dry steering stability and the noise performance of the tire are improved as compared with the edge portion of the opening portion with the groove or the sipe.

In the pneumatic tire 10, the inner second land portion 32 includes the narrow groove 323, and the narrow groove 323 is open at an edge portion on the tire equatorial plane CL side of the inner second land portion 32 at one end portion and terminates near the maximum width position 3211 of the chamfered portion 321 or is connected to the maximum width position 3211 at the other end portion. In this configuration, the lateral groove opened in the central portion of the chamfered portion 321 is a wide lateral groove 322, and the lateral groove closed or opened at the maximum width position 3211 of the chamfered portion 321 is a narrow groove 323, which has the following advantages. That is, (a) has an advantage that rigidity of the inner second land portion 32 is secured and dry performance of the tire is secured, as compared with a structure (not shown) in which all grooves disposed in the inner second land portion 32 are wide lateral grooves. In addition, (b) has an advantage that the drainage of the inner second land portion 32 is improved and the wet steering stability of the tire is improved, as compared with a configuration (not shown) in which all the grooves disposed in the inner second land portion 32 are narrow grooves or sipes. Further, (c) compared with a configuration (not shown) in which wide lateral grooves are opened to the maximum width position of the chamfered portion and narrow grooves or sipes are terminated or opened at the central portion of the chamfered portion, since the rigidity of the inner second land portion 32 at the maximum width position 3211 of the chamfered portion 321 can be ensured while ensuring the drainage action from the lateral grooves 322 to the chamfered portion 321, there is an advantage that both the dry steering stability performance and the wet steering stability performance of the tire can be achieved.

In addition, in the pneumatic tire 10, the outer second land portion 34 and the outer shoulder land portion 35 include a plurality of types of closed lateral grooves 41A, 41B (see fig. 2) having different extending lengths from each other. The shortest first closed lateral groove 41A has a tire width direction extension length L1_ min and the longest second closed lateral groove 41B has a tire width direction extension length L1_ max of 1.10. ltoreq.L 1_ max/L1_ min. ltoreq.3.00. In this structure, since the plurality of kinds of closed lateral grooves 41A, 41B having the extension lengths different from each other are arranged at predetermined intervals in the tire circumferential direction, the terminating portions of the closed lateral grooves 41A, 41B in at least one land portion (the outer second land portion 34 in fig. 2) are inevitably arranged in the tire circumferential direction while being offset from each other in the tire width direction. Therefore, compared to a configuration in which the left and right end portions of the closed lateral groove are aligned with the positions in the tire width direction (not shown), the longer lateral groove portion (the portion on the outer second land portion 34 side of the second closed lateral groove 41B in fig. 2) is disposed on the tread surface of 1 land portion (the outer second land portion 34 in fig. 2), and the wide ground contact region is formed between the adjacent longer lateral groove portions. This has the advantage of efficiently improving the wet performance and dry performance of the tire.