CN109664685B

CN109664685B - Pneumatic tire

Info

Publication number: CN109664685B
Application number: CN201811105477.0A
Authority: CN
Inventors: 安永智一
Original assignee: Toyo Tire and Rubber Co Ltd
Current assignee: Toyo Tire Corp
Priority date: 2017-10-13
Filing date: 2018-09-21
Publication date: 2021-01-15
Anticipated expiration: 2038-09-21
Also published as: JP2019073129A; JP6949654B2; DE102018216400B4; CN109664685A; DE102018216400A1

Abstract

The invention provides a pneumatic tire with ensured grounding performance, rigidity balance in the tire circumferential direction and drainage performance. A first narrow groove (30) is provided on one side in the width direction of a main groove (20) extending straight in the tire circumferential direction, and a second narrow groove (40) provided on the other side, one end of the first narrow groove and one end of the second narrow groove (40) being open at the main groove (20) extending straight, the other end being closed in the land portions (24, 26), the first narrow groove and the second narrow groove (40) being curved in the same direction in the tire circumferential direction, a portion (32) of the first narrow groove on the one end side than the curved portion (31) and a portion (42) of the second narrow groove (40) on the one end side than the curved portion (41) extending in the same direction, a portion (43) of the second narrow groove (40) on the other end side than the curved portion (41) being further toward the tire circumferential direction than a portion (33) of the first narrow groove on the other end side than the curved portion (31).

Description

Pneumatic tire

The application claims the priority of the Japanese patent application 2017-199828 based on the Japanese patent application 2017-199828 (application date: 10/13 of 2017). The present application includes the entire contents of Japanese patent application No. 2017-199828.

Technical Field

The present invention relates to a pneumatic tire.

Background

The following pneumatic tires have been known in the past: on both sides in the width direction of a main groove extending straight along the tire circumferential direction, a narrow groove extending in the tire width direction is provided, one end of which is open at the main groove and the other end is closed in a land portion (see, for example, patent document 1). Such a narrow groove separates the land portion at the main groove side portion in the tire circumferential direction, and therefore, the land portion is excellent in ground contact property.

Patent document 1: japanese patent No. 5781566

Disclosure of Invention

However, in the pneumatic tire described above, since the rigidity is different between the portion where the narrow groove is provided and the portion where the narrow groove is not provided, the rigidity of the land portion is not uniformized in the tire circumferential direction. In addition, the fine groove extending in the tire width direction has a relatively small effect on drainage.

Accordingly, an object of the present invention is to provide a pneumatic tire capable of ensuring a ground contact property, a rigidity balance in the tire circumferential direction, and a drainage property.

A pneumatic tire according to an embodiment includes a first narrow groove on one side in a width direction of a main groove extending straight in a tire circumferential direction, and a second narrow groove on the other side, the first narrow groove and the second narrow groove being formed such that: one end is open at the main groove extending in a straight shape, and the other end is closed in a land portion, and the pneumatic tire is characterized in that the first narrow groove and the second narrow groove are bent in the same direction in the tire circumferential direction, a portion of the first narrow groove closer to the one end side than the bent portion and a portion of the second narrow groove closer to the one end side than the bent portion extend obliquely in the same direction with respect to the tire circumferential direction, and a portion of the second narrow groove closer to the other end side than the bent portion is more toward the tire circumferential direction than a portion of the first narrow groove closer to the other end side than the bent portion.

The pneumatic tire of the embodiment has the above-described features, and thus can ensure the ground contact property, the rigidity balance in the tire circumferential direction, and the drainage property.

Drawings

Fig. 1 is a width-direction cross-sectional view of a pneumatic tire 1 of the embodiment.

Fig. 2 is a tread pattern of the embodiment.

Fig. 3 is a view of the center main groove 10 as viewed from the outer side in the tire radial direction (the third narrow groove 28 is omitted for simplicity).

Fig. 4 is a view of the central main groove 10 as viewed from the tangential direction of the tire equator E (wherein the third sipe 28 is omitted for simplicity).

Fig. 5 is a sectional view of the central main groove 10 at the line a-a in fig. 3.

Fig. 6 is a view of the first sipe 30 and the second sipe 40 as viewed from the outer side in the tire radial direction.

Fig. 7(a) is a cross-sectional view of the slit portion 32 of the first narrow groove 30 at the line B-B in fig. 6. Fig. 7(b) is a sectional view of the sipe portion 33 of the first fine groove 30 at the line C-C in fig. 6.

Fig. 8(a) is a cross-sectional view of the slit portion 42 of the second groove 40 at the line D-D in fig. 6. Fig. 8(b) is a cross-sectional view of the sipe portion 43 of the second fine groove 40 at the line E-E in fig. 6.

Fig. 9 is a view of the shoulder rib 26 as viewed from the outer side in the tire radial direction.

Fig. 10 is a sectional view of the fourth sipe 50 at line F-F in fig. 9.

Fig. 11 is a view showing a 3-dimensional sipe 55. Fig. 11(a) is a view of the fourth sipe 50 as viewed from the tire surface. Fig. 11(b) is a view showing one wall surface of the fourth narrow groove 50. Fig. 11(c) is a cross-sectional view of the fourth fine groove 50 on the plane parallel to the ground plane at the position of line G-G in fig. 11 (b).

Description of the reference numerals

E … tire equator, 1 … pneumatic tire, 2 … bead portion, 2a … bead core, 2b … bead filler, 3 … tread rubber, 4 … sidewall rubber, 5 … carcass ply, 6 … inner liner, 7 … belt, 10 … central main groove, 11 … long groove portion, 12 … short groove portion, 13 … groove bottom, 14 … convex portion, 14a … right convex portion, 14b … left convex portion, 15 … concave portion, 16 … conical surface, 17 … wall portion, 20 … shoulder main groove, 22 … grounding end, 24 … central rib portion, 26 shoulder … rib portion, 28 … third narrow groove, 29 … conical surface, 30 … first narrow groove, 31 … curved portion, 32 … slit portion, 33 … slit portion, 34 … conical surface, 3635 conical surface, 40 … second narrow groove wall portion, 3641 curved portion, 3642 slit portion, …, fourth … slit portion, 33 …, … narrow groove portion, 33 …, … wall portion, … thin …, … groove portion, … thin groove portion, …, 55 … 3 dimensional sipes, 56 … wall portions, 57 … crest portions, 58 … trough portions.

Detailed Description

Embodiments will be described with reference to the drawings. The following embodiments are merely examples, and the scope of the invention is not limited thereto.

In the following description, the width of the groove and the tapered surface provided in the groove means: the length in the direction perpendicular to the direction in which the center line of the groove bottom of the groove extends in a plane parallel to the tire contact surface. In addition, the load state means: the pneumatic tire is assembled to a regular rim in a rim assembly manner, and is filled with a regular internal pressure and loaded with a regular load. Here, the regular rim means: standard rims defined in JATMA, TRA, ETRTO, and other specifications. In addition, the normal load means: the maximum load specified in the specification. The normal internal pressure is: an internal pressure corresponding to the maximum load.

1. Sectional structure of pneumatic tire 1

As shown in fig. 1 by way of example, on both sides in the tire width direction of a pneumatic tire 1, bead portions 2 are provided. The bead portion 2 includes: a bead core 2a made of steel wire, which is wound in a circular shape; and a rubber bead filler 2b provided radially outside the bead core 2 a. The carcass ply 5 is laid on the bead portions 2 on both sides in the tire width direction. The carcass ply 5 is a sheet-like member in which a plurality of cords aligned in a direction orthogonal to the tire circumferential direction are covered with rubber. The carcass ply 5 forms a skeleton shape of the pneumatic tire 1 between the bead portions 2 on both sides in the tire width direction, and is folded back around the bead portions 2 from the inner side toward the outer side in the tire width direction, thereby enclosing the bead portions 2. On the inner side of the carcass ply 5, there are adhered: a sheet-like inner liner 6 made of rubber having low air permeability.

On the outer side in the tire radial direction of the carcass ply 5, there are provided: 1 or more layers of belts 7. The belt 7 is: a member in which a plurality of steel cords are covered with rubber. On the tire radial direction outer side of the belt 7, there are provided: and a tread rubber 3 having a surface (hereinafter referred to as "ground contact surface") contacting a road surface. Further, sidewall rubbers 4 are provided on both sides of the carcass ply 5 in the tire width direction. In addition to the above components, components such as a belt under-pad, a chafer, and the like are provided according to the functional requirements of the pneumatic tire 1.

2. Outline of tread Pattern

On the surface of the tread rubber 3, there are formed: the tread pattern illustrated in fig. 2. In this tread pattern, as a main groove which is a wide groove extending in the tire circumferential direction, there are provided: a center main groove 10 at the center in the tire width direction, and shoulder main grooves 20 on both sides in the tire width direction. Further, there are provided: a center rib 24 sandwiched between the center main groove 10 and the shoulder main groove 20, and a shoulder rib 26 sandwiched between the shoulder main groove 20 and the ground contact 22. Further, the rib means: a land portion continuous in the tire circumferential direction. Here, the land portion means: a part which is formed by dividing the groove and has a grounding surface. In addition, the ground terminal 22 means: the tire width direction end of the contact surface in a loaded state.

Further, on the tire equator E side of the shoulder main groove 20, there are provided: the first narrow groove 30 is provided on the ground contact end 22 side of the shoulder main groove 20: and a second sipe 40. Further, on both sides in the width direction of the center main groove 10, there are provided: and a third sipe 28. Further, the shoulder rib 26 is provided with: and a fourth sipe 50. The

sipes

30, 40, 28, and 50 are arranged at equal intervals or substantially equal intervals in the tire circumferential direction. The configuration of these

sipes

30, 40, 28, 50 will be described later.

3. Structure of main trench

As shown in fig. 2 to 4, the central main groove 10 extends in a zigzag shape along the tire circumferential direction. That is, the center main groove 10 is zigzag when viewed from the outside in the tire radial direction. More specifically, the central main groove 10 includes: a long groove portion 11 extending obliquely with respect to the tire circumferential direction; and a short groove portion 12 inclined with respect to the tire circumferential direction and extending in a direction different from that of the long groove portion 11. The central main groove 10 is formed by alternately arranging the long groove portions 11 and the short groove portions 12.

Since the central main groove 10 is zigzag in this manner, the following are formed in the central main groove 10 at the boundary between the long groove portion 11 and the short groove portion 12: a convex portion 14 protruding into the central main groove 10, and a concave portion 15 facing the convex portion 14 with the central main groove 10 therebetween.

In the present embodiment, as shown in fig. 4, the right-side convex portion 14a and the left-side convex portion 14b do not have an overlapping portion in the tire circumferential direction with respect to the center line of the central main groove 10, and are spaced apart from each other between the right-side convex portion 14a and the left-side convex portion 14 b: the gap L in the tire width direction. Further, it is judged that there is a gap L in the groove bottom 13.

However, the top portion of the right convex portion 14a protruding into the groove and the top portion of the left convex portion 14b protruding into the groove are at the same position in the tire width direction, and these top portions may be arranged on 1 circle in the tire circumferential direction. In addition, the right convex portion 14a and the left convex portion 14b may have an overlapping portion in the tire circumferential direction (in other words, the right convex portion 14a and the left convex portion 14b may partially overlap as viewed in the tire circumferential direction).

As shown in fig. 3 to 5, tapered surfaces 16 are provided on both sides in the width direction of the central main groove 10. The tapered surfaces 16 are: as shown in fig. 4, the tapered surface 16 is a surface continuous from the ground surface to the back side of the central main groove 10: the corner of the center rib 24 on the center main groove 10 side is chamfered. The width of the central main groove 10 toward the open end of the ground plane is increased due to the tapered surface 16. Further, the tapered surface 16 may reach the ground plane, but as shown in fig. 5, there may be formed between the tapered surface 16 and the ground plane: and a wall portion 17 having a minute height (for example, about 0.5 mm). In the portion where the tapered surface 16 is provided, the width of the central main groove 10 gradually increases as it approaches the ground plane. The angle of the tapered surface 16 with respect to the ground plane is, for example, 40 ° to 50 °.

As shown in fig. 3, the width of the tapered surface 16 gradually increases from the position of the concave portion 15 of the central main groove 10 toward the position of the convex portion 14 on both sides in the width direction of the central main groove 10. As a result, the angle θ 1 of the open end of the center main groove 10 facing the ground contact surface with respect to the tire circumferential direction is smaller than the angle θ 2 of the groove bottom 13 of the center main groove 10 with respect to the tire circumferential direction.

Further, the greater the width of the tapered surface 16, the greater the depth toward the groove bottom 13. Therefore, the depth of the tapered surface 16 gradually increases from the position of the concave portion 15 of the central main groove 10 toward the position of the convex portion 14. The depth at the deepest position of the tapered surface 16 is, for example: half the depth of the central main trench 10 to the trench bottom 13.

In the present embodiment, the tapered surface 16 described above is provided at: both the long groove portion 11 and the short groove portion 12.

On the other hand, the shoulder main groove 20 extends not in a zigzag shape but in a straight shape along the tire circumferential direction.

4. Structure of fine groove

As shown in fig. 2, the first narrow groove 30 extends from the straight shoulder main groove 20 toward the tire equator E. One end of the first sipe 30 is open at the shoulder main groove 20 and the other end is closed within the center rib 24.

The first narrow groove 30 is curved when viewed from the outer side in the tire radial direction. The bent portion 31 is formed at an obtuse angle. As shown in fig. 6, a portion of the first narrow groove 30 closer to the shoulder main groove 20 than the bent portion 31 is a slit portion 32 having a large width. On the other hand, a portion of the first narrow groove 30 closer to the leading end side than the curved portion 31 is a sipe portion 33 having a small width. In the loaded state, the slit portion 32 is not closed, but the sipe portion 33 is closed. The width of the slit portion 32 is, for example, 1.9mm to 2.1mm, and the width of the sipe portion 33 is, for example, 0.7mm to 0.9 mm.

As shown in fig. 6 and 7, the sipe portion 33 has a tapered surface 34 at a portion that is the inside (the side where the obtuse angle is formed) of the curve of the first narrow groove 30. The width of the sipe portion 33 toward the opening end of the ground contact surface is increased due to the tapered surface 34. The tapered surfaces 34 are: a surface continuous from the ground contact surface to the back side of the sipe portion 33 in the vicinity of the ground contact surface. The tapered surface 34 may reach the ground plane, or as shown in fig. 7(b), between the tapered surface 34 and the ground plane: and a wall 35 having a minute height (for example, about 0.5 mm). In addition, the tapered surface 34 does not reach the bottom of the sipe portion 33. By providing the tapered surface 34, the width of the sipe portion 33 gradually increases as it approaches the ground contact surface. The angle of the tapered surface 34 with respect to the ground plane is, for example, 40 ° to 50 °. The width of the tapered surface 34 gradually increases as it goes from the front end of the first sipe 30 toward the curved portion 31, and reaches the maximum at the curved portion 31. As shown in fig. 7(a), the slit portion 32 is not provided with such a tapered surface. Therefore, the tapered surface 34 is provided only in the sipe portion 33 in the first narrow groove 30.

As shown in fig. 2, the second narrow groove 40 extends from the straight shoulder main groove 20 toward the ground contact end 22. One end of the second sipe 40 is open at the shoulder main groove 20 and the other end is closed within the shoulder rib 26.

The second sipe 40 is curved when viewed from the outer side in the tire radial direction. The bent portion 41 is formed at an obtuse angle. As shown in fig. 6, the second narrow groove 40 is a slit portion 42 having a large width on the shoulder main groove 20 side of the bent portion 41. On the other hand, the portion of the second narrow groove 40 on the tip end side of the curved portion 41 is a sipe portion 43 having a small width. In the loaded state, the slit portion 42 is not closed, but the sipe portion 43 is closed. The width of the slit portion 42 is, for example, 1.9mm to 2.1mm, and the width of the sipe portion 43 is, for example, 0.7mm to 0.9 mm.

As shown in fig. 6 and 8, the sipe portion 43 has a tapered surface 44 at a portion that is the inside (the side where the obtuse angle is formed) of the curve of the second narrow groove 40. The width of the sipe portion 43 toward the opening end of the ground contact surface is increased due to the tapered surface 44. The tapered surface 44 is: a surface continuous from the ground contact surface to the back side of the sipe portion 43 in the vicinity of the ground contact surface. The tapered surface 44 may reach the ground plane, or as shown in fig. 8(b), between the tapered surface 44 and the ground plane: and a wall portion 45 having a minute height (for example, about 0.5 mm). In addition, the tapered surface 44 does not reach the bottom of the sipe portion 43. By providing the tapered surface 44, the width of the sipe portion 43 is gradually increased as approaching the ground contact surface. The angle of the tapered surface 44 with respect to the ground plane is, for example, 40 ° to 50 °. The width of the tapered surface 44 gradually increases from the front end of the second sipe 40 toward the curved portion 41, and reaches a maximum at the curved portion 41. Such a tapered surface is not provided in the slit portion 42. Therefore, the tapered surface 44 is provided only in the sipe portion 33 in the first narrow groove 30.

As shown in fig. 6, the slit portion 32 of the first narrow groove 30 and the slit portion 42 of the second narrow groove 40 extend obliquely in the same direction with respect to the tire circumferential direction. The slit portion 32 of the first groove 30 and the slit portion 42 of the second groove 40 are aligned with each other.

In addition, the first sipe 30 and the second sipe 40 are curved in the same direction in the tire circumferential direction. That is, the

sipe portions

33 and 43 extend from the

curved portions

31 and 41 of the

narrow grooves

30 and 40 in the same direction in the tire circumferential direction. Further, the sipe portion 43 of the second fine groove 40 is more oriented in the tire circumferential direction than the sipe portion 33 of the first fine groove 30. That is, the inclination angle of the sipe portion 43 of the second fine groove 40 with respect to the tire circumferential direction is smaller than the inclination angle of the sipe portion 33 of the first fine groove 30 with respect to the tire circumferential direction. The sipe portion 43 is a kind of sub groove. The minor groove means: the grooves have a width smaller than the width of the main grooves, and extend continuously for 1 turn in the tire circumferential direction, or intermittently extend in the tire circumferential direction like the sipe portion 43.

As shown in fig. 2, the first narrow groove 30 and the second narrow groove 40 are provided on both sides in the tire width direction. The first narrow groove 30 and the second narrow groove 40 are arranged in opposite directions with respect to the tire circumferential direction on one side and the other side in the tire width direction. The first narrow groove 30 and the second narrow groove 40 are offset in the tire circumferential direction on one side and the other side in the tire width direction. That is, the position of the first narrow groove 30 on one side in the tire width direction and the position of the first narrow groove 30 on the other side in the tire width direction do not coincide with each other in the tire width direction, and the position of the second narrow groove 40 on one side in the tire width direction and the position of the second narrow groove 40 on the other side in the tire width direction do not coincide with each other at all in the tire width direction.

The third fine groove 28 extends from the central main groove 10 in a zigzag shape in a direction toward the ground terminal 22. One end of the third sipe 28 is open at the central main groove 10 and the other end is closed within the central rib 24. The third sipe 28 is not curved but extends in a straight shape.

The third narrow groove 28 has a width substantially equal to the width of the

slit portions

32 and 42. As shown in fig. 2, the third narrow groove 28 includes: such that the third sipe 28 has an increased width taper 29 towards the open end of the ground plane. The tapered surfaces 29 are: a surface continuous from the ground surface to the back side of the third fine groove 28 in the vicinity of the ground surface. Further, the tapered surface 29 may reach the ground plane, and as in the case of the first narrow groove 30, between the tapered surface 29 and the ground plane, there may be formed: a wall portion having a minute height (for example, about 0.5 mm). In addition, the tapered surface 29 does not reach the bottom of the third sipe 28. By providing the tapered surface 29, the width of the third fine groove 28 gradually increases as it approaches the ground plane. The angle of the tapered surface 29 with respect to the ground plane is, for example, 40 ° to 50 °. The width of the tapered surface 29 gradually decreases in a direction from the central main groove 10 toward the ground terminal 22.

As shown in fig. 2 and 9, the fourth narrow groove 50 extends in the tire width direction in the shoulder rib 26. One end of the fourth sipe 50 is closed in the shoulder rib 26, and the other end is open outward in the tire width direction from the ground contact end 22.

The fourth narrow groove 50 is curved at a portion on the one end side on the tire equator E side when viewed from the tire radial direction outer side. The specific positions of the bent portion 51 are: for example, the fourth sipe 50 is located from the one end of the fourth sipe 50 toward the ground contact end 22 side and in the tire width direction at a length within 1/4 of the length of the fourth sipe 50 in the tire width direction (the length of the fourth sipe from the one end to the ground contact end 22 in the tire width direction). The bent portion 51 is formed at an obtuse angle of 140 ° to 160 °, for example.

As shown in fig. 10, the fourth sipe 50 is formed as: a closed sipe in the loaded state. The width of the fourth fine groove 50 is, for example, 0.7mm to 0.9 mm. The depth of the fourth fine groove 50 gradually decreases from the bent portion 51 toward the one end side.

As shown in fig. 9 and 10, a tapered surface 54 is provided at a portion inside the curve of the fourth narrow groove 50. The width of the fourth sipe 50 towards the open end of the ground plane increases because of the tapered surface 54. The tapered surfaces 54 are: a surface continuous from the ground surface to the back side of the fourth fine groove 50 in the vicinity of the ground surface. The tapered surface 54 may reach the ground plane, or as shown in fig. 10, between the tapered surface 54 and the ground plane: and a wall portion 56 of a minute height (for example, about 0.5 mm). In addition, the tapered surface 54 does not reach the bottom of the fourth sipe 50. By providing the tapered surface 54, the width of the fourth fine groove 50 is gradually increased as approaching the ground plane. The angle of the tapered surface 54 with respect to the ground plane is, for example, 35 ° to 45 °. The width of the tapered surface 54 gradually increases as it goes from the ground terminal 22 toward the bent portion 51, and reaches the maximum at the bent portion 51. A tapered surface 54 is also provided in the fourth sipe 50 on the tire equator E side of the curved portion 51 so as to be continuous with the curved portion 51.

The portion of the fourth sipe 50 closer to the ground end 22 side than the bent portion 51 is: the 3-dimensional sipe 55 illustrated in fig. 11. The 3-dimensional sipe 55 means: a sipe whose shape changes in the depth direction thereof. As shown in fig. 11(c), the 3-dimensional sipe 55 of the embodiment is formed as: the wave-shaped structure has a wave-like shape composed of a peak portion 57 and a valley portion 58 in a cross section of a plane parallel to the ground plane at a portion deeper than the ground plane. Further, as shown in fig. 11(b), the peak portions 57 and the valley portions 58 extend in a zigzag shape in the depth direction of the 3-dimensional sipe 55.

As shown in fig. 2, the fourth narrow groove 50 is provided on both sides in the tire width direction. Fourth sipe 50 is configured to: on both sides in the tire width direction, the directions are opposite to each other with respect to the tire circumferential direction. However, the fourth narrow groove 50 may be provided only on either side in the tire width direction, and in this case, it is preferably provided on the OUT side (vehicle outer side) when mounted on a vehicle.

As shown in fig. 9, the second sipe 40 is present in the shoulder rib 26 in addition to the fourth sipe 50. The fourth fine groove 50 has an overlapping portion with the sipe portion 43 of the second fine groove 40 in the tire width direction. The one end of the fourth fine groove 50 is close to the sipe portion 43 of the second fine groove 40, but is closed before the sipe portion 43 and does not communicate with the sipe portion 43.

5. Effects of the embodiments

In the pneumatic tire 1 of the embodiment, the first narrow groove 30 is provided on one side in the width direction of the shoulder main groove 20, and the second narrow groove 40 is provided on the other side in the width direction of the shoulder main groove 20, and therefore, the center rib 24 and the shoulder rib 26 exhibit good ground contact properties. Further, since the first narrow groove 30 and the second narrow groove 40 are curved, when a large stress is applied to the center rib 24 and the shoulder rib 26, portions on both sides of the first narrow groove 30 and the second narrow groove 40 can mesh with each other in the tire width direction, and the lateral rigidity (rigidity in the tire width direction) of the center rib 24 and the shoulder rib 26 is ensured. Here, although the lateral rigidity is likely to be reduced in the vicinity of the shoulder main groove 20 extending straight along the tire circumferential direction, the first narrow groove 30 and the second narrow groove 40 can compensate for the lateral rigidity in the vicinity of the shoulder main groove 20 by bending.

Further, since the slit portion 32 of the first sipe 30 and the slit portion 42 of the second sipe 40 extend obliquely in the same direction with respect to the tire circumferential direction and the first sipe 30 and the second sipe 40 are curved in the same direction in the tire circumferential direction, the first sipe 30 and the second sipe 40 are arranged such that: staggered in the tire circumferential direction. As a result, the center rib 24 and the shoulder ribs 26 have uniform lateral rigidity and uniform longitudinal rigidity (rigidity in the tire circumferential direction).

Further, since the sipe portion 43 of the second sipe 40 is oriented in the tire circumferential direction more than the sipe portion 33 of the first sipe 30, the shoulder rib 26 provided with the second sipe 40 is easily drained along the tire circumferential direction. Further, the sipe portion 43 of the second fine groove 40 is more toward the tire circumferential direction than the sipe portion 33 of the first fine groove 30 (i.e., the sipe portion 43 of the second fine groove 40 extends more toward the tire circumferential direction and the sipe portion 33 of the first fine groove 30 extends more toward the tire width direction in comparison), so that it is also possible to bring: the shoulder rib 26 provided with the second sipe 40 can maintain the effect of longitudinal rigidity, so that the center rib 24 provided with the first sipe 30 exhibits a better grounding property.

As described above, in the pneumatic tire 1 of the embodiment, the ground contact property, the rigidity balance in the tire circumferential direction, and the drainage property are ensured. As a result, the performance such as steering stability of the pneumatic tire 1 is ensured.

Here, the above-described effect can be obtained even if the second sipe 40, which is a sipe portion further extending in the tire circumferential direction, is provided in either the center rib portion 24 or the shoulder rib portion 26. Therefore, even if the first narrow groove 30 is provided in the shoulder rib 26 and the second narrow groove 40 is provided in the center rib 24, contrary to the embodiment, the above-described effects can be obtained.

However, the rib on the side of the ground contact end 22 (i.e., the shoulder rib 26 in the present embodiment) greatly affects the braking performance. Furthermore, the drainage and longitudinal stiffness also affect the braking performance. Therefore, when the second narrow groove 40 having a certain effect on drainage and longitudinal rigidity is provided in the shoulder rib 26 as in the present embodiment, braking performance is improved.

In addition, the rib on the tire equator E side (i.e., the center rib 24 in the present embodiment) greatly affects the steering stability. Furthermore, the grounding property also affects the steering stability. Therefore, if the first narrow groove 30, which is more effective in terms of the grounding property, is provided in the center rib 24, the steering stability is improved.

As described above, in the present embodiment, the slit portion 32 of the first sipe 30 and the slit portion 42 of the second sipe 40 extend obliquely in the same direction with respect to the tire circumferential direction, and the first sipe 30 and the second sipe 40 are curved in the same direction in the tire circumferential direction. In addition, in the present embodiment, since the slit portion 32 of the first sipe 30 and the slit portion 42 of the second sipe 40 are aligned on the same line, the first sipe 30 and the second sipe 40 are reliably displaced in the tire circumferential direction. Therefore, the rigidity of the center rib 24 and the shoulder rib 26 in the vicinity of the shoulder main groove 20 is uniformed in the tire circumferential direction.

In the first narrow groove 30 and the second narrow groove 40, the width of the

slit portions

32 and 42 on the shoulder main groove 20 side of the

bent portions

31 and 41 is large, and therefore, the grounding performance is ensured. Further, the portions before the

bent portions

31 and 41 are the

sipe portions

33 and 43 having a small width, so that rigidity is ensured. Further, by providing the

sipe portions

33 and 43 with tapered surfaces, rigidity in the vicinity of the

bent portions

31 and 41 is ensured.

The central main groove 10 is formed in a zigzag shape, so that rigidity of the central rib 24 is secured, and drainage is secured by the tapered surface 16. Therefore, the rigidity and drainage of the entire tire are ensured by the combination of the central main groove 10 and the first and

second sipes

30 and 40. The fourth narrow groove 50 can improve the grounding performance of the shoulder rib 26 and ensure drainage performance by opening outward in the tire width direction. Therefore, the combination of the fourth narrow groove 50 and the first and second

narrow grooves

30 and 40 ensures the ground contact property and drainage property of the entire tire.

6. Modification example

The above embodiment may be variously omitted, replaced, or modified within a range not departing from the gist of the present invention.

In the case where the center main groove does not extend in a zigzag shape but in a straight shape along the tire circumferential direction as in the above-described embodiment, the first narrow groove 30 and the second narrow groove 40 may be provided in the center main groove.

In the first and second narrow grooves, the portions closer to the main groove side than the bent portion are not limited to the slit portions having a large width, and the portions closer to the front (closed end side) than the bent portion are not limited to the sipe portions having a small width. For example, the first and second narrow grooves may be formed entirely by slit portions having a width larger than the width of the

sipe portions

33 and 43 in the above embodiment.

Claims

1. A pneumatic tire comprising a main groove extending straight in a tire circumferential direction, the main groove having a first narrow groove on one side in a width direction and a second narrow groove on the other side, wherein the first narrow groove and the second narrow groove are formed such that: one end of the main trench is opened at the main trench extending in a straight shape, and the other end is closed in the land part,

the pneumatic tire is characterized in that it is,

the first sipe and the second sipe are curved in the same direction in the tire circumferential direction,

a portion of the first sipe located closer to the one end side than the curved portion and a portion of the second sipe located closer to the one end side than the curved portion extend obliquely in the same direction with respect to the tire circumferential direction,

a portion of the second sipe located closer to the other end side than the bent portion is located further toward the tire circumferential direction than a portion of the first sipe located closer to the other end side than the bent portion,

in the first narrow groove and the second narrow groove, a portion closer to the other end side than a bent portion is: a sipe having a width smaller than a width of a portion closer to the one end side than the bent portion, the sipe being provided at a portion inside the bend of the sipe: a tapered surface that increases the width toward the open end of the ground plane.

2. A pneumatic tire according to claim 1,

the first narrow groove is provided on the tire equator side and the second narrow groove is provided on the ground contact end side with the main groove extending straight.

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

the portion of the first narrow groove closer to the one end side than the bent portion and the portion of the second narrow groove closer to the one end side than the bent portion are on the same straight line.

4. A pneumatic tire according to claim 1,

the tapered surface is not provided at a portion closer to the one end side than the bent portion, and a width of the tapered surface gradually increases from a leading end of the first narrow groove and the second narrow groove toward the bent portion and becomes maximum at the bent portion.

5. A pneumatic tire according to claim 1 or 2,

the bent portions of the first sipe and the second sipe form an obtuse angle.