CN109774385B - Pneumatic tire - Google Patents

Abstract

A pneumatic tire (10) is provided with, in a tread portion (16): a plurality of main grooves (36) extending in the tire circumferential direction, and a plurality of land portions (38, 40, 42) defined by the main grooves (36), wherein the main grooves (36) include: a shoulder main groove (36B) provided on the outer side Wo in the tire width direction, and land portions (38, 40, 42) comprising: a shoulder land portion (42) formed on the outer side Wo of the shoulder main groove (36B) in the tire width direction, the shoulder land portion (42) comprising: a plurality of small holes (50) provided at intervals along the tire circumferential direction on the tire width direction inner side Wi of the ground contact edge E, the small holes (50) including: and a curved portion (53) that curves toward the tire width direction inner side Wi with respect to the depth direction.

Description

Pneumatic tire

Technical Field

The present invention relates to a pneumatic tire.

Background

Pneumatic tires have a tendency to: in general, the ground contact pressure is high near the ground contact edge of the shoulder land portion of the tread portion during running. As a result, uneven wear may occur in which the wear amount near the ground contact edge of the shoulder land portion becomes larger than that of the other land portion of the tread portion. As a method for suppressing such uneven wear, as disclosed in japanese patent laid-open nos. 8-258513 and 5-294112, there are cases where: a plurality of small holes opened on the surface of the tread. According to this method, the rigidity near the ground contact end of the shoulder land portion can be reduced, and the ground contact pressure can be made uniform.

Disclosure of Invention

The ground contact pressure at the shoulder land portion tends to gradually decrease from the outer side toward the inner side in the tire width direction in some cases. However, according to the tire disclosed in the above document, the rigidity can be reduced at the position where the small hole is provided, but the rigidity is hardly reduced at other positions, and therefore, it is difficult to make the ground contact pressure uniform, and the uneven wear generated in the vicinity of the ground contact end of the shoulder land portion cannot be sufficiently suppressed.

Accordingly, an object of the present invention is to provide a pneumatic tire capable of suppressing uneven wear occurring in a shoulder land portion.

According to the present embodiment, the following aspects [1] to [9] are provided.

[1] A pneumatic tire, comprising, in a tread portion: a plurality of main grooves extending in a tire circumferential direction, and a plurality of land portions defined by the main grooves, wherein the main grooves include: a shoulder main groove provided on the outer side in the tire width direction, the land portion including: a shoulder land portion formed on the outer side of the shoulder main groove in the tire width direction, the shoulder land portion including: a plurality of small holes provided at intervals along a tire circumferential direction on an inner side of a ground contact end in a tire width direction, the small holes including: and a bent portion that is bent inward in the tire width direction with respect to the depth direction.

[2] The pneumatic tire according to the above [1], wherein the shoulder land portion includes: and a sipe extending in the tire circumferential direction between the small hole and the ground contact end.

[3] The pneumatic tire according to the above [2], wherein the small hole is deeper than the narrow groove.

[4] The pneumatic tire according to the above [2] or [3], wherein the cross section of the small hole is circular, and a distance from an opening edge of the small hole to an opening edge of the narrow groove is: the diameter of the small hole is 1-1.5 times.

[5] The pneumatic tire according to any one of the above [1] to [4], wherein the small hole is deeper than the shoulder main groove.

[6] The pneumatic tire according to any one of the above [1] to [5], wherein the small hole includes: a first straight portion extending radially from the tread surface toward a tire, the curved portion being configured to: and is continuous with the inner side of the first straight portion.

[7] The pneumatic tire according to the above [6], wherein the small hole includes: a second straight portion extending in a tire radial direction, and provided to: is continuous with the inner side of the bending part.

[8] The pneumatic tire according to the above [7], wherein the small hole includes an enlarged portion provided with: is continuous with the inner side of the second straight part,

the enlarged portion is constituted by a cavity longer than the second straight portion in the tire width direction.

[9] The pneumatic tire according to the above [8], wherein the enlarged portion is not expanded toward the outer side in the tire width direction than the second straight portion but expanded toward the inner side in the tire width direction.

According to the present invention, the plurality of small holes provided in the shoulder land portion include: the small holes are distributed widely in the tire width direction with respect to the curved portion curved inward in the tire width direction with respect to the depth direction, and are arranged at positions that are located more deeply toward the tire width direction inner side, that is, toward the shoulder land portion. Therefore, the amount of decrease in rigidity near the ground contact edge of the shoulder land portion can be gradually reduced from the outer side toward the inner side in the tire width direction, the ground contact pressure becomes uniform as compared with the case where a small hole having no curved portion is provided, and uneven wear occurring in the shoulder land portion can be effectively suppressed.

Drawings

Fig. 1 is a half sectional view of a pneumatic tire according to a first embodiment of the present invention.

Fig. 2 is a plan view of a tread portion of the pneumatic tire of fig. 1.

Fig. 3 is a perspective view of a shoulder land portion of the pneumatic tire of fig. 1.

Fig. 4 is a plan view of a tread portion of a pneumatic tire according to a second embodiment of the present invention.

Fig. 5 is a perspective view of a shoulder land portion of a pneumatic tire according to a second embodiment of the present invention.

Description of the symbols:

10 … pneumatic tire, 12 … bead portion, 14 … sidewall portion, 16 … tread portion, 18 … support portion, 20 … carcass ply, 22 … bead core, 24 … inner liner, 26 … belt, 28 … tread rubber, 36 … main groove, 36a … center main groove, 36B … shoulder main groove, 38 … center land portion, 40 … middle land portion, 42 … shoulder land portion, 50 … small hole, 51 … opening edge, 52 … first straight portion, 53 … curved portion, 54 … second straight portion, 55 … enlarged portion, 60 … narrow groove, 61 … opening edge.

Detailed Description

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

In the present specification, the ground terminal means: the pneumatic tire is assembled to a regular rim, is vertically placed on a flat road surface in a state filled with a regular internal pressure, and is applied with a regular load, and the tire width direction end of a ground contact surface which is in contact with the road surface. The normal rim is: a rim determined for each tire in accordance with a specification system including a specification under which the tire is based; for example, it is "standard rim" if JATMA, "design rim" if TRA, and "measurement rim" if ETRTO. The normal internal pressure is: in a specification system including the specification to which the tire is subjected, the air pressure determined for each tire in accordance with each specification is the highest air pressure if JATMA, the maximum value described in the table "tire load limit under various cold inflation pressures" if TRA, and the "inflation pressure" if ETRTO, although the normal air pressure is 180kPa in the case where the tire is used for a passenger vehicle. In addition, the normal load is: in a specification system including the specification to which the tire is subjected, the load determined for each tire in accordance with each specification is the maximum load capacity if JATMA, the maximum value described in the above table if TRA, and the "load capacity" if ETRTO, but when the tire is used for a passenger vehicle, the load corresponding to 88% of the load.

In addition, as for the above-mentioned respective dimensions in the present specification, except for the case where specifically mentioned, the above-mentioned respective dimensions are: the pneumatic tire is mounted on a regular rim and filled with regular internal pressure, and has dimensions in a normal state without load.

(first embodiment)

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

Fig. 1 is a right side half sectional view obtained by cutting a pneumatic tire 10 according to the embodiment at a meridian section including a tire axis. Here, since the tire is bilaterally symmetric, the left half is omitted from the drawings.

The pneumatic tire 10 of fig. 1 includes: a pair of left and right bead portions 12; a pair of left and right sidewall portions 14 extending radially outward from the bead portion 12; a tread portion 16 constituting a tread surface; and a pair of left and right support portions 18 disposed on the inner side of the tread portion 16 in the tire radial direction. Here, the support portion 18 is: a boundary region between the tread portion 16 and the sidewall portion 14 is provided: the tread portion 16 and the sidewall portion 14 are connected to each other.

The pneumatic tire 10 includes: and a carcass ply 20 annularly disposed between the pair of bead portions 12. The pair of bead units 12 are embedded with: an annular bead core 22.

The carcass ply 20 is locked to the bead core 22 in the bead portion 12 from the tread portion 16 via the support portion 18 and the sidewall portion 14, and the carcass ply 20 reinforces the above-described respective portions 12, 14, 16, 18. In this example, both ends of the carcass ply 20 are folded back around the bead cores 22 from the inner side to the outer side in the tire width direction and locked. The carcass ply 20 is provided with: a liner 24 for maintaining air pressure.

The carcass ply 20 is composed of at least 1 ply, in this example, 1 ply, in which organic fiber cords are arranged obliquely with respect to the tire circumferential direction at a predetermined angle (for example, 70 ° to 90 °) and are covered with an upper rubber. As the cord constituting the carcass ply 20, for example, an organic fiber cord of polyester fiber, rayon fiber, aramid fiber, nylon fiber, or the like is preferably used.

The sidewall portion 14 is provided with, on the outer side of the carcass ply 20 (i.e., on the tire outer surface side): sidewall rubber 32. Further, in the bead portion 12, on the outer peripheral side of the bead core 22, there are disposed: and a bead filler 34 made of a hard rubber material and extending outward in the radial direction of the tire in a tapered shape.

A belt 26 is disposed on the outer circumferential side of the carcass ply 20 in the tread portion 16. That is, in the tread portion 16, a belt 26 is provided between the carcass ply 20 and the tread rubber 28. The belt 26 is formed of a plurality of cross belt cords arranged so that the belt cords are inclined at a predetermined angle (for example, 10 ° to 35 °) with respect to the tire circumferential direction. As the belt cord, a steel cord or an organic fiber cord having a higher tension is used.

On the surface of tread portion 16, there are provided: 4 main grooves 36 extending in the tire circumferential direction. Specifically, the main groove 36 includes: a pair of central main grooves 36A disposed on both sides with the tire equatorial plane CL therebetween; and a pair of shoulder main grooves 36B provided on the tire width direction outer sides Wo of the pair of center main grooves 36A. The tire width direction outer side Wo is: on the side away from the tire equatorial plane CL in the tire width direction W.

In the tread portion 16, the 4 main grooves 36 described above form, between the 2 central main grooves 36A: the center land portion 38 has, between the center main groove 36A and the shoulder main groove 36B: the intermediate land portion 40 is formed on the tire width direction outer sides Wo of the 2 shoulder main grooves 36B with: shoulder land portions 42. The tire-width-direction outer end of the tread surface of the tire-shoulder land portion 42 constitutes a tread ground contact end E, and is connected to: a support portion 18 extending inward in the tire radial direction and constituting an upper portion of the tire side surface.

Further, the shoulder land portion 42 is provided with: a plurality of small holes 50 opened in the tread surface 42 a.

The plurality of apertures 50 are: a recess having a circular cross section and recessed toward the tire radial direction inner side Ri, and including: and a bent portion 53 bent toward the tire width direction inner side Wi with respect to the depth direction (tire radial direction inner side Ri). Specifically, the pinhole 50 includes: a cylindrical first straight portion 52 extending from an opening edge 51 formed on the tread surface 42a in parallel with the tire radial direction R; a curved portion 53 provided continuously from the back side of the first straight portion 52; a second straight portion 54 provided continuously to the back side of the curved portion 53; and an enlarged portion 55 provided continuously to the back side of the second straight portion 54.

The bent portion 53 is provided: the first straight portions 52 extending in the tire radial direction R are curved toward the tire width direction inner side Wi. Thus, the second straight portion 54 provided on the back side of the curved portion 53 is disposed: further toward the tire width direction inner side Wi than the first straight portion 52.

The second straight portion 54 has: a cylindrical shape extending from the back side of the bent portion 53 in parallel with the tire radial direction R. At the bottom of the second straight portion 54, there are provided: the enlarged portion 55 is formed of a cavity (a cavity that is long in the tire width direction) having a width larger than the widths of the first straight portion 52 and the second straight portion 54. The enlarged portion 55 is configured to: the cavity portion does not extend further toward the tire width direction outer side Wo than the second straight portion 54 but extends toward the tire width direction inner side Wi. The tire radial direction inner side Ri of the enlarged portion 55 constitutes a bottom of the small hole 50. The small holes 50 are provided at intervals along the tire circumferential direction on the tire width direction inner side Wi of the ground contact edge E.

Here, referring to fig. 2 and 3, an example of the size of the small hole 50 is given, and when the groove depth f of the shoulder main groove 36B is 10 to 15mm and the tread ground contact width (the interval between the left and right ground contact edges E) L is 200 to 245mm, the hole depth a of the small hole 50 may be 10.5 to 18mm, the diameter c of the small hole 50 may be 1.5 to 3.0mm, the interval E of the small hole 50 in the tire circumferential direction may be 1.5 to 9mm, and the distance g from the opening edge 51 of the small hole 50 formed in the tread surface 42a to the ground contact edge E may be 2 to 4.5 mm.

In the present embodiment, the plurality of small holes 50 provided on the tire width direction inner side Wi of the ground contact edge E of the shoulder land portion 42 include: and a curved portion 53 curved toward the tire width direction inner side Wi with respect to the depth direction. Therefore, the small hole 50 can be arranged in a wide range in the tire width direction W, without increasing the diameter of the small hole 50, and can be arranged at a deeper position in the shoulder land portion as the inner side Wi in the tire width direction approaches. Accordingly, the amount of decrease in rigidity near the ground contact edge E of the shoulder land portion 42 can be gradually reduced from the outer side Wo toward the inner side Wi in the tire width direction, so that the ground contact pressure near the ground contact edge E of the shoulder land portion 42 becomes uniform, and uneven wear occurring in the shoulder land portion 42 can be effectively suppressed.

In the present embodiment, since the small hole 50 provided in the shoulder land portion 42 includes the bent portion 53, even if a stone enters the small hole 50, the stone can be prevented from entering the groove side by the bent portion 53.

In the present embodiment, the small hole 50 includes, on the tread surface 42a side of the curved portion 53: since the first straight portion 52 extends from the opening edge 51 in parallel with the tire radial direction R, it can be easily pulled out from the small hole 50 when the tire after vulcanization molding is removed from the mold: the protrusions for molding the pinholes 50 can suppress the occurrence of chipping around the pinholes 50 during mold release.

In the present embodiment, when the cross section of the small hole 50 is circular, the stress is dispersed over the entire circumference of the small hole 50 without being concentrated in a predetermined direction around the small hole 50, and therefore, the occurrence of cracks can be suppressed.

In the present embodiment, the diameter c of the small hole 50 is preferably 1.5 to 3.0 mm. If the diameter c of the small hole 50 is 1.5mm or more, the rigidity in the vicinity of the ground contact edge E of the shoulder land portion 42 can be effectively reduced, and if the diameter c of the small hole 50 is 3.0mm or less, it can be suppressed: one of the step-in side and the step-out side of the small hole 50 generates tread edge wear that is more greatly worn than the other.

In the present embodiment, the hole depth a of the small hole 50 is preferably set to be equal to or greater than the groove depth f of the shoulder main groove 36B. This makes it possible to equalize the ground contact pressure in the vicinity of the ground contact edge E of the shoulder land portion 42 until the final stage of tire wear.

(second embodiment)

Next, a second embodiment of the present invention will be described with reference to fig. 4 and 5. Note that the same portions as those in the first embodiment will not be described, and different portions will be described.

In the present embodiment, a narrow groove 60 is provided on the tire width direction inner side Wi of the ground contact edge E of the shoulder land portion 42 in addition to the small hole 50.

Specifically, the sipes 60 extend in the tire circumferential direction between the ground contact edge E of the shoulder land portion 42 and the plurality of small holes 50. The narrow groove 60 divides the shoulder land portion 42 into: a main body land portion 421 on the tire width direction inner side Wi, and a sacrificial land portion 422 on the tire width direction outer side Wo. A plurality of small holes 50 are provided in the main body land portion 421 and on the tire width direction outer side Wo of the narrow groove 60 (in the vicinity of the narrow groove 60).

Further, the sipe 60 may be recessed from an opening edge 61 formed on the tread surface 42a of the shoulder land portion 42 in parallel to the tire radial direction R so as to be parallel to the first straight portion 52 and the second straight portion 54 of the small hole 50.

Here, referring to fig. 4 and 5, as an example of the size of the small hole 50, when the groove depth f of the shoulder main groove 36B is 10 to 15mm and the tread ground contact width L is 200 to 245mm, the hole depth a ' of the small hole 50 is 10.5 to 18mm, the groove depth B ' of the fine groove 60 is 10 to 15mm, the diameter c ' of the small hole 50 is 1.5 to 3.0mm, the width m ' of the fine groove 60 is 1.5 to 3.0mm, the interval (the distance from the opening edge 61 of the fine groove 60 formed on the tread surface 42a to the opening edge 51 of the small hole 50) d ' between the fine groove 60 and the small hole 50 is 2 to 4.5mm, the interval E ' of the small hole 50 in the tire circumferential direction is 1.5 to 9mm, and the distance g ' from the opening edge 51 of the small hole 50 formed on the tread surface 42a to the ground contact edge E is 5.5 to 12 mm.

In the present embodiment, the tire width direction inner side Wi of the ground contact edge E of the shoulder land portion 42 is provided with: a sipe 60 extending in the tire circumferential direction, and provided on a tire width direction inner side Wi of the sipe 60: a plurality of small holes 50 arranged side by side at intervals in the tire circumferential direction. Thus, the tire shoulder land portion 42 can be formed on the tire width direction outer side Wo: the land portion 422 is sacrificed, so that: substantially aiding in tire performance is greater uneven wear of the body land portion 421. In addition, since the plurality of small holes 50 are provided on the tire width direction outer side Wo of the main body land portion 421, the ground contact pressure of the main body land portion 421 can be made uniform in the tire width direction, and uneven wear can be effectively suppressed.

The orifice 50 further includes: the curved portion 53 that curves toward the tire width direction inner side with respect to the depth direction, and the bottom of the small hole 50 are arranged such that: since the narrow groove 60 is spaced apart from the open end side (tread surface 42a side), the stress concentration between the bottom of the small hole 50 and the bottom of the narrow groove 60 can be relaxed, and the occurrence of cracking can be suppressed.

In the present embodiment, the hole depth a 'of the small hole 50 is preferably set to be larger than the groove depth b' of the fine groove 60 (that is, a '> b'), and for example, the hole depth a 'of the small hole 50 may be set to be larger than 1 time and 1.2 times or less (b' < a '≦ 1.2 b') of the groove 60. By setting the hole depth a 'and the groove depth b' in this manner, the ground contact pressure of the main body land portion 421 can be made uniform by the small holes 50, and uneven wear can be suppressed until the end of tire wear. In addition, since the depth of the small hole 50 is different from the depth of the narrow groove 60, the stress concentration between the bottom of the small hole 50 and the bottom of the narrow groove 60 can be relaxed, and the occurrence of cracking can be suppressed.

In the present embodiment, the distance d' between the narrow groove 60 and the small hole 50 is preferably: the diameter c of the small hole 50 is 1 to 1.5 times (c 'is more than or equal to d' is more than or equal to 1.5 c). If the distance d 'between the fine groove 60 and the small hole 50 is equal to or greater than the diameter c' of the small hole 50, the distance between the fine groove 60 and the small hole 50 can be secured, and the occurrence of chipping of the main body land portion 421 can be suppressed, and if the distance d 'between the fine groove 60 and the small hole 50 is equal to or less than 1.5 times the diameter c' of the small hole 50, the contact pressure can be made uniform on the tire width direction outer side Wo of the main body land portion 421, and uneven wear can be effectively suppressed.

(modification example)

The above embodiments are provided as examples and are not intended to limit the scope of the present invention. The new embodiment can be implemented in other various manners, and various omissions, substitutions, and changes can be made without departing from the spirit of the present invention.

For example, the orifice 50 may have: in this case, in addition to the above-described effects, the rigidity in the vicinity of the ground contact edge of the shoulder land portion can be reduced in multiple stages from the outer side Wo in the tire width direction toward the inner side Wi, and uneven wear can be further suppressed.

For example, the small hole 50 may be terminated at the bent portion 53 without providing the second straight portion 54 at the back side of the bent portion 53, or may be terminated at the back side of the bent portion 53 by providing the enlarged portion 55. In this case, the above-described effects can be obtained.

Claims (6)

1. A pneumatic tire, comprising, in a tread portion: a plurality of main grooves extending in a tire circumferential direction, and a plurality of land portions defined by the main grooves,

the pneumatic tire is characterized in that it is,

the main trench includes: a tire shoulder main groove arranged on the outer side of the tire width direction,

the land portion includes: a shoulder land portion formed on the outer side of the shoulder main groove in the tire width direction,

the shoulder land portion includes: a plurality of small holes provided at intervals along the tire circumferential direction on the inner side of the ground contact end in the tire width direction,

the small hole is provided with: a bending portion that bends toward the inner side in the tire width direction with respect to the depth direction,

the shoulder land portion includes: a sipe extending in a tire circumferential direction between the small hole and the ground contact end,

the small holes are deeper than the fine grooves,

the cross section of the small hole is circular, and the distance from the opening edge of the small hole to the opening edge of the fine groove is as follows: the diameter of the small hole is 1-1.5 times.

2. A pneumatic tire according to claim 1,

the small hole is deeper than the shoulder main groove.

3. A pneumatic tire according to claim 1,

the small hole is provided with: a first straight portion extending radially from the tread surface toward the tire,

the curved portion is configured to: and is continuous with the inner side of the first straight portion.

4. A pneumatic tire according to claim 3,

the small hole is provided with: a second straight portion extending in a tire radial direction, and provided to: is continuous with the inner side of the bending part.

5. A pneumatic tire according to claim 4,

the small hole is provided with an enlarged part which is configured to: is continuous with the inner side of the second straight part,

the enlarged portion is constituted by a cavity longer than the second straight portion in the tire width direction.

6. A pneumatic tire according to claim 5,

the enlarged portion is not expanded toward the tire width direction outer side than the second straight portion but expanded toward the tire width direction inner side.

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