CN118056688A

CN118056688A - Pneumatic tire

Info

Publication number: CN118056688A
Application number: CN202311077009.8A
Authority: CN
Inventors: 白樫良尚
Original assignee: Toyo Tire Corp
Current assignee: Toyo Tire Corp
Priority date: 2022-11-18
Filing date: 2023-08-24
Publication date: 2024-05-21
Also published as: JP2024073977A

Abstract

The present invention provides a pneumatic tire capable of realizing excellent steering stability while ensuring good drainage. A pneumatic tire (1) according to an embodiment is provided with a tread (10) and is specified with respect to the mounting direction of a vehicle. The tread (10) has: a first shoulder main groove (20) extending along the tire circumferential direction; and a first shoulder block (30) that is partitioned by the first shoulder main groove (20) and is disposed on the vehicle outside. A slope (36) extending obliquely to the first shoulder main groove (20) adjacent to the first shoulder block (30) is formed on the inner side surface in the tire axial direction of the first shoulder block (30), and the slope (36) extends in a direction inclined at a predetermined angle with respect to the tire circumferential direction. The ground contact surface of the tread (10) has a rectangle ratio of 0.55-0.85.

Description

Pneumatic tire

Technical Field

The present invention relates to a pneumatic tire, and more particularly, to a tire whose mounting direction with respect to a vehicle is specified.

Background

Conventionally, a pneumatic tire is widely known that includes a tread having a main groove extending in a tire circumferential direction and a lateral groove extending in a direction intersecting the main groove, and is specified in a mounting direction of the pneumatic tire to a vehicle (for example, refer to patent document 1). In the tread pattern disclosed in patent document 1, inclined surfaces are formed on groove wall surfaces of the main grooves and the lateral grooves. By forming the inclined surface on the groove wall surface, the groove area is increased, and good drainage can be obtained.

[ Prior Art literature ]

[ Patent literature ]

Patent document 1: japanese patent application laid-open No. 2019-94004

Disclosure of Invention

Problems to be solved by the invention

However, as a result of the study by the present inventors, it was found that: in such a tire having a groove wall surface formed with a slope, the block rigidity decreases according to the shape of the slope and the shape of the ground contact surface of the tread, and the steering stability decreases. It is an important problem to realize a pneumatic tire excellent in steering stability while ensuring good drainage.

Means for solving the problems

The pneumatic tire according to the present invention includes a tread, and an assembling direction of the pneumatic tire with respect to a vehicle is specified, wherein the tread includes: a first shoulder main groove extending along the tire circumferential direction; and a first shoulder block which is divided by the first shoulder main groove and is disposed on the vehicle outer side, wherein an inclined surface extending obliquely to the first shoulder main groove side adjacent to the first shoulder block is formed on the side surface on the inner side in the tire axial direction of the first shoulder block, the inclined surface extends in a direction inclined at a prescribed angle with respect to the tire circumferential direction, and the ground contact surface of the tread has a rectangular rate of 0.55 to 0.85.

Effects of the invention

According to the pneumatic tire of the present invention, excellent steering stability can be achieved while ensuring good drainage.

Drawings

Fig. 1 is a perspective view of a pneumatic tire as an example of an embodiment.

Fig. 2 is a plan view of a pneumatic tire as an example of an embodiment, and is an enlarged view of a part of a tread.

Fig. 3 is a plan view of a pneumatic tire as an example of an embodiment, and shows a first shoulder block in an enlarged manner.

Fig. 4 is a perspective view of a pneumatic tire as an example of an embodiment, and shows a first shoulder block in an enlarged manner.

Fig. 5 is a cross-sectional view taken along line AA in fig. 3.

Fig. 6 is a cross-sectional view taken along line BB in fig. 3.

Fig. 7 is a sectional view of fig. 3 taken along line CC.

Fig. 8 is a plan view of a pneumatic tire as an example of an embodiment, and is a diagram showing a first intermediate block.

Fig. 9 is a perspective view of a pneumatic tire as an example of an embodiment, and is a view showing a first intermediate block.

Fig. 10 is a cross-sectional view taken along line DD in fig. 8.

Fig. 11 is a sectional view taken along line EE in fig. 8.

Fig. 12 is a cross-sectional view taken along line FF in fig. 8.

Fig. 13 is a diagram schematically showing the shape of the ground contact surface of the tread.

Fig. 14 is a perspective view of a pneumatic tire as an example of an embodiment, and is a view showing the outside of the vehicle.

Reference numerals illustrate:

1. Pneumatic tire

10. Tire tread

11. Sidewall of a tire

12. Tire bead

13. Side rib

14. Carcass body

15. Air-tight layer

16. Belted layer

17. Belted layer reinforcement

18. Crown ply

19. Edge ply

20. First shoulder main groove

21. A first central main groove

22. A second central main groove

23. Second shoulder main groove

30. First shoulder block

32. 72 Horizontal knife groove

33. 63, 73 Transverse grooves

34. 37, 441, 442 Steps

35. 55, 451, 452, 651, 652 Pocket

36. 46, 47 Inclined plane

40. First intermediate block

50. Center pattern block

60. Second intermediate block

70. Second shoulder block

311. 312, 411, 412, 413, 611, 612 Longitudinal knife groove

321. Wide width part

361. 461, 471 First inclined plane

362. 462, 472 Second inclined plane

362A outer end

412A widened portion

731. Shallow groove part

732. Narrow width portion.

Detailed Description

An example of an embodiment of a pneumatic tire according to the present invention will be described in detail below with reference to the drawings. The embodiments described below are merely examples, and the present invention is not limited to the following embodiments. The present invention includes a configuration in which the constituent elements of the embodiments described below are selectively combined.

Fig. 1 is a perspective view showing a part of a pneumatic tire 1 as an example of an embodiment, and a cross-sectional structure of the tire is collectively shown. As shown in fig. 1, the pneumatic tire 1 includes a tread 10, and the tread 10 is a portion that contacts a road surface. The tread 10 has a main groove extending in the tire circumferential direction, and a first shoulder block 30 and a first intermediate block 40 partitioned by the main groove, and the tread 10 is formed in a ring shape in the tire circumferential direction.

Inclined surfaces extending obliquely to the adjacent main groove sides are formed on the inner side surface in the tire axial direction of the first shoulder block 30 and on the both side surfaces in the tire axial direction of the first intermediate block 40, as will be described in detail later. The inclined surface includes a portion extending along the tire circumferential direction and a portion extending in a direction inclined at a predetermined angle with respect to the tire circumferential direction. The ground contact surface of the tread 10 has a rectangular rate of 0.55 to 0.85.

The pneumatic tire 1 is a tire specified with respect to the fitting direction of the vehicle, and is opposite in direction of the vehicle fitting on the right and left sides of the vehicle. The tread 10 has different tread patterns on the left and right sides of the tire equator CL (see fig. 2). The equator CL is an imaginary line along the tire circumferential direction passing through the tire axial direction midpoint of the tread 10. In the present specification, the term "left and right" is used for convenience of description, and refers to the left and right in the traveling direction of the vehicle in a state where the pneumatic tire 1 is mounted on the vehicle. The pneumatic tire 1 is suitable for example for a summer tire of an Electric Vehicle (EV) such as an electric vehicle (HV) or a Hybrid Vehicle (HV) having high acceleration performance, or a Sport Utility Vehicle (SUV) having a heavy vehicle weight.

A plurality of main grooves are formed in the tread 10. The number of main grooves is not particularly limited, and in the present embodiment, four main grooves each composed of two center main grooves 21, 22 and two shoulder main grooves 20, 23 are formed. The four main grooves further improve the water drainage.

The main groove located outside the vehicle out of the center main grooves 21, 22 is set as a first center main groove 21, and the main groove located inside the vehicle out of the center main grooves 21, 22 is set as a second center main groove 22. Further, the main groove located on the vehicle outside of the shoulder main grooves 20, 23 is referred to as a first shoulder main groove 20, and the main groove located on the vehicle inside of the shoulder main grooves 20, 23 is referred to as a second shoulder main groove 23. Each main groove is not curved in the tire axial direction but is formed straight along the tire circumferential direction. The main grooves may have the same width and depth, but in the present embodiment, at least the widths of the first shoulder main groove 20 and the first center main groove 21 and the widths of the second shoulder main groove 23 and the second center main groove 22 are different from each other.

The tread 10 has a first shoulder block 30, which is divided by a first shoulder main groove 20 extending in the circumferential direction and disposed on the vehicle outer side, and a second shoulder block 70, which is divided by a second shoulder main groove 23 extending in the circumferential direction and disposed on the vehicle inner side. In other words, the pneumatic tire 1 is mounted to the vehicle such that the first shoulder block 30 is located on the vehicle outside and the second shoulder block 70 is located on the vehicle inside. The block is a portion protruding outward in the tire radial direction from a position corresponding to the bottom of the main groove, and is also referred to as a land.

The tread 10 has a center block 50 divided by a first center main groove 21 and a second center main groove 22 extending in the circumferential direction and located on the equator CL. In addition, the tread 10 has a first intermediate block 40 formed between the first shoulder block 30 and the center block 50, and a second intermediate block 60 formed between the center block 50 and the second shoulder block 70.

The pneumatic tire 1 includes a pair of sidewalls 11 bulging outward in the tire axial direction, and a pair of beads 12. The bead 12 is a part fixed to the rim of the wheel, for example having a bead core and bead filler. The sidewalls 11 and beads 12 are formed in a ring shape along the tire circumferential direction, and constitute side surfaces of the pneumatic tire 1. Sidewalls 11 extend from both ends of the tread 10 in the tire axial direction toward the center in the tire radial direction.

The pneumatic tire 1 may have side ribs 13 formed between the ground contact ends E1 and E2 (see fig. 2) of the tread 10 and the outermost portion of the sidewall 11 in the tire axial direction. The ground contact end E1 is the ground contact end on the vehicle outside, the ground contact end E2 is the ground contact end on the vehicle inside, and the ground contact ends E1 and E2 are respectively present in the first shoulder block 30 and the second shoulder block 70. The side rib 13 protrudes outward in the tire axial direction and is formed in a ring shape along the tire circumferential direction. The portion of the pneumatic tire 1 from the ground contact ends E1, E2 or the vicinity thereof to the left and right side ribs 13 is also referred to as a shoulder or bearing (buttress) region.

In general, the tread 10 and the sidewalls 11 are composed of different kinds of rubber. The side ribs 13 may be made of the same rubber as the ground contact surface of the tread 10 or may be made of a different rubber from the ground contact surface of the tread 10. In this specification, the ground terminals E1, E2 are defined as: the tire axial direction both ends of the region (ground contact surface) which comes into contact with the flat road surface when a predetermined load is applied in a state where the unused pneumatic tire 1 is mounted on the normal rim and filled with air so as to become a normal internal pressure. In the case of a passenger tire, the predetermined load is a load corresponding to 88% of the normal load.

Here, the "normal Rim" is a Rim standardized by a tire, and is "standard Rim" if JATMA, and is "Measuring Rim" if TRA and ETRTO. In the case of JATMA, the "normal internal pressure" is the "highest air pressure", in the case of TRA, the "normal internal pressure" is the maximum value described in table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, the "normal internal pressure" is "INFLATION PRESSURE". The normal internal pressure is usually 180kPa in the case of a tire for a passenger vehicle, but the normal internal pressure is 220kPa in the case of a tire described as Extra Load or reinfored. For "normal LOAD", if JATMA, the "normal LOAD" is "maximum LOAD CAPACITY", if TRA, the "normal LOAD" is the maximum value described in table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and if ETRTO, the "normal LOAD" is "LOAD CAPACITY".

The pneumatic tire 1 includes a carcass 14, an inner liner 15, and a belt layer 16. The carcass 14 is a cord layer covered with rubber, and forms a skeleton of the pneumatic tire 1 that is resistant to load, impact, air pressure, and the like. The inner liner 15 is a rubber layer provided on the inner circumferential surface of the carcass 14, and holds the air pressure of the pneumatic tire 1. The belt layer 16 is a reinforcing belt disposed between the rubber constituting the tread 10 and the carcass 14. The belt layer 16 strongly tightens the carcass 14 to improve the rigidity of the pneumatic tire 1.

The pneumatic tire 1 is used as a tire designated with respect to the mounting direction of the vehicle, and therefore preferably has a display for showing the mounting direction with respect to the vehicle. The display showing the mounting direction may be characters, symbols, explanatory drawings, or the like showing the inside or outside of the vehicle, and the configuration thereof is not particularly limited. In general, a symbol called a sequence (serial) is provided on the side surface of the pneumatic tire 1, and the sequence may be used as a display showing the fitting direction.

The sequence includes information such as a size code, a manufacturing time (manufacturing year week), a manufacturing place (manufacturing factory code), and the like. The fitting direction of the pneumatic tire 1 with respect to the vehicle may also be determined by providing a sequence only on the side surface (sidewall 11) of the pneumatic tire 1 facing the outside of the vehicle, or providing a different sequence on the side surface facing the outside of the vehicle than the side surface facing the inside. Specific examples include a manufacturing factory code and a size code provided on both side surfaces of the pneumatic tire 1, and a manufacturing year round provided only on a side surface facing the outside of the vehicle.

The tread 10 of the pneumatic tire 1 will be described in detail below with reference to fig. 2. Fig. 2 is a plan view of the pneumatic tire 1, and shows a part of the tread 10.

As shown in fig. 2, the tread 10 has a center block 50 at the center in the tire axial direction, and has a tread pattern asymmetric to the left and right with respect to the equator CL. Hereinafter, the region closer to the ground end E1 than the equator CL is referred to as a first region, and the region closer to the ground end E2 than the equator CL is referred to as a second region. In the case of a tire in which the tread pattern of the pneumatic tire 1 is assembled to the vehicle such that the first region is located on the vehicle outside and the second region is located on the vehicle inside, excellent steering stability can be achieved while ensuring good drainage. As described above, the pneumatic tire 1 is a summer tire used on a road surface where no frozen or snow is present, and is suitable for use in EV, HV, or SUV.

In the present embodiment, the center of the center block 50 in the axial direction is offset toward the land E1 side from the equator CL. Therefore, the first and second center main grooves 21, 22 disposed adjacently on both sides of the center block 50 in the tire axial direction are formed at positions at different distances from the equator CL.

The four main grooves may be formed with the same width, but in the present embodiment, the width W ₂₂ of the second center main groove 22 and the width W ₂₃ of the second shoulder main groove 23 formed in the second region are larger than the width W ₂₀ of the first shoulder main groove 20 and the width W ₂₁ of the first center main groove 21 formed in the first region. By widening the width of the main groove formed in the second region, good drainage is ensured, and the wet braking performance is improved. In the present specification, unless otherwise specified, the width of the groove means a width along a contour surface α (see fig. 5 described later), which is a surface along the ground contact surface of the tread 10.

The first center main groove 21 may be formed wider than the width of the first shoulder main groove 20. In addition, the second center main groove 22 and the second shoulder main groove 23 may have the same width as each other. An example of the width of the groove is 12.0 to 13.5mm in width W ₂₀, 14.5 to 16.0mm in width W ₂₁, and 17.0 to 18.5mm in width W ₂₂、W₂₃.

The four main grooves may be formed with the same depth as each other, and the center main grooves 21, 22 may be formed deeper than the shoulder main grooves 20, 23. The depth of the groove refers to the depth of the deepest portion of the groove unless otherwise specified. More specifically, the shortest distance from the contour surface α to the groove bottom at the deepest portion is referred to. An example of the depth of each main groove is 7 to 15mm.

Typically, at least any one of the four main grooves is provided with a wear indicator (not shown). The wear indication is a protrusion disposed at the groove bottom, and serves as an index for confirming the wear level of the tread rubber.

In the first region of the tread 10, a first shoulder block 30, a first intermediate block 40, and a center block 50 are formed in this order from the ground contact end E1 side. In addition, a first shoulder main groove 20 and a first center main groove 21 are formed in the first region. The first shoulder main groove 20 intercepts the first shoulder block 30 from the first intermediate block 40, and the first center main groove 21 intercepts the first intermediate block 40 from the center block 50.

In the second region of the tread 10, a second shoulder block 70, a second intermediate block 60, and a center block 50 are formed in this order from the ground contact end E2 side. In the second region, a second center main groove 22 and a second shoulder main groove 23 are formed. The second center main groove 22 intercepts the center block 50 from the second intermediate block 60, and the second shoulder main groove 23 intercepts the second intermediate block 60 from the second shoulder block 70.

The first shoulder block 30, the first intermediate block 40, the center block 50, the second intermediate block 60, and the second shoulder block 70 are arranged parallel to each other across the main groove. In the present embodiment, the width of the first shoulder block 30 is larger than the width of the second shoulder block 70. In addition, the width of the first intermediate block 40 is larger than the width of the second intermediate block 60. Also, the width of the center block 50 is smallest among the widths of all the blocks.

Inclined surfaces 36, 46, 47 extending obliquely to the adjacent main groove side are formed on the inner side surface in the tire axial direction of the first shoulder block 30 and on the both side surfaces in the tire axial direction of the first intermediate block 40, as will be described in detail later. The inclined surfaces 36, 46, 47 include portions extending along the tire circumferential direction and portions extending in a direction inclined at a predetermined angle with respect to the tire circumferential direction. The central block 50, the second intermediate block 60, and the second shoulder block 70 are not beveled.

A plurality of sipes are formed in the first shoulder block 30 along the tire circumferential direction. In the present specification, the sipe is a narrow groove having a width smaller than a transverse groove described later, and means a groove having a groove width of 1.0mm or less. The groove width does not include the width of a step described later. In the pneumatic tire 1, the sipe plays a role of adjusting the rigidity of the block, for example, and contributes to both good riding comfort performance and braking performance. In the present embodiment, two longitudinal sipes 311, 312 are formed in the first shoulder block 30 along the tire circumferential direction.

The first shoulder block 30 has a lateral sipe 32 and a lateral sipe 33 extending outward in the tire axial direction from a longitudinal sipe 311. In the present specification, the term "groove (also referred to as" sipe ") means both a form in which the groove extends along the tire axial direction and a form in which the groove extends at an inclination angle of 45 ° or less, preferably 30 ° or less, with respect to the tire axial direction. In the same manner as the main groove extending in the tire circumferential direction, the main groove may be formed in a zigzag shape while being bent at an inclination angle of 45 ° or less with respect to the tire circumferential direction.

The lateral sipes 32 and the lateral sipes 33 are alternately arranged at intervals in the tire circumferential direction. One ends of the lateral cutter groove 32 and the lateral cutter groove 33 are opened in the longitudinal cutter groove 311, and the other ends of the lateral cutter groove 32 and the lateral cutter groove 33 extend to the vicinity of the side rib 13 beyond the ground end E1. By extending the lateral sipes 32 and 33 to the vicinity of the side ribs 13, drainage is improved.

The first shoulder block 30 has a sipe 35 extending from the first shoulder main groove 20 toward the longitudinal sipe 312 at an inclination angle of approximately 45 ° with respect to the tire axial direction. The sipes 35 are formed in plural at intervals in the tire circumferential direction. One end of the sipe 35 is open to the first shoulder main groove 20, and the other end of the sipe 35 is open to the longitudinal sipe 312. In the present embodiment, the sipe 35 (similar to other sipes) is formed in a linear shape, but the present invention is not limited thereto. For example, the sipe 35 may be formed in a curved shape, or may have a bent shape.

A step 34 extending outward from the groove wall surface is formed on one groove wall surface of the sipe 35. In the present specification, the step means a substantially flat portion of the block formed on the inner side in the tire radial direction than the ground contact surface of the tread 10, and is a portion other than the sipe and the lateral groove. The step 34 is continuously formed along the extending direction of the sipe 35. The width of the step 34 gradually increases toward the first shoulder main groove 20. In addition, a step 34 is formed between the inclined surface 36 and the first shoulder main groove 20.

Three longitudinal sipes 411, 412, 413 are formed in the first intermediate block 40 along the tire circumferential direction. Further, the first intermediate block 40 is formed with a sipe 451 extending from the first shoulder main groove 20 toward the longitudinal sipe 411 at an inclination angle of approximately 45 ° with respect to the tire axial direction. One end of the blade groove 451 opens into the first shoulder main groove 20, and the other end of the blade groove 451 opens into the longitudinal blade groove 411. Further, the first intermediate block 40 is formed with a sipe 452 extending from the first center main groove 21 toward the longitudinal sipe 413 at an inclination angle of approximately 45 ° with respect to the tire axial direction. One end of the sipe 452 opens into the first center main groove 21, and the other end of the sipe 452 opens into the longitudinal sipe 413.

Preferably, the sipe 451 and the sipe 452 are formed on substantially the same straight line. Further, it is more preferable that the sipe 451, the sipe 452, and the sipe 35 formed in the first shoulder block 30 be formed on substantially the same straight line. This can improve drainage.

Steps 441 and 442 extending outward from the groove wall surfaces are formed on one groove wall surface of the blade grooves 451 and 452, respectively. The step 441 is continuously formed along the extending direction of the sipe 451, and the step 442 is continuously formed along the extending direction of the sipe 452. The width of the step 441 gradually increases as it goes toward the first shoulder main groove 20, and is formed between the inclined surface 46 and the first shoulder main groove 20. In addition, the width of the step 442 gradually becomes larger toward the first central main groove 21, and is formed between the inclined surface 47 and the first central main groove 21.

It is preferable that the steps 441 and 442 have a point-symmetrical shape with respect to an arbitrary point on the center line of the first intermediate block 40 in the tire axial direction. Further, it is preferable that the step 441 is formed so as to face the step 34 formed on the inner side in the tire axial direction of the first shoulder block 30 with the first shoulder main groove 20 interposed therebetween. Further, it is more preferable that the step 441 and the step 34 have a point-symmetrical shape with respect to an arbitrary point on the center line of the first shoulder main groove 20 in the tire axial direction. This makes it possible to achieve both good drainage and excellent handling stability.

A sipe 55 extending from the first center main groove 21 toward the inner side of the center block 50 at an inclination angle of approximately 45 ° with respect to the tire axial direction is formed in the center block 50. One end of the sipe 55 opens into the first central main groove 21, and the other end of the sipe 55 terminates within the central block 50. The other end of the sipe 55 is located closer to the ground end E2 than the equator CL. Preferably, sipe 55 is formed in substantially the same line as sipes 451, 452 formed in first intermediate block 40.

The center block 50 is formed with a slope 56 inclined from one groove wall surface of the sipe 55 toward the upper surface of the center block 50. The inclined surface 56 is formed along the extending direction of the sipe 55, and extends from the first center main groove 21 to the vicinity of the equator CL. The inclined surface 56 may be formed from the middle of the groove wall surface of the sipe 55 toward the upper surface, or may be formed from the groove bottom of the sipe 55 toward the upper surface. The inclined surface 56 may be formed on the groove wall surface of all the sipes 55, or may be formed on the groove wall surface of a part of the sipes 55. By forming the inclined surface 56, the rigidity of the center block 50 can be improved, and uneven wear of the center block 50 can be suppressed.

Two longitudinal sipes 611, 612 are formed in the second intermediate block 60 along the tire circumferential direction. The second intermediate block 60 has a sipe 651 extending from the second center main groove 22 toward the longitudinal sipe 611 at a predetermined inclination angle with respect to the tire axial direction. One end of the knife slot 651 is open to the second central main slot 22, and the other end of the knife slot 651 is open to the longitudinal knife slot 611. Further, the second intermediate block 60 is formed with a sipe 652 extending from the second shoulder main groove 23 toward the longitudinal sipe 612 at a predetermined inclination angle with respect to the tire axial direction. One end of the sipe 652 opens in the second shoulder main groove 23, and the other end of the sipe 652 opens in the longitudinal sipe 612.

The inclination angles of the sipe 651 and the sipe 652 with respect to the tire axial direction may be the same or different. The inclination angle of the sipes 651, 652 with respect to the tire axial direction may be smaller than the inclination angle of the sipes 451, 452 formed in the first intermediate block 40 with respect to the tire axial direction. The inclination angle of the pockets 651, 652 with respect to the tire axial direction is, for example, 20 ° to 50 °.

The knife groove 651 forms one between two adjacent lateral grooves 63 in the tire circumferential direction. The knife groove 651 is preferably formed at a position approximately bisected in the tire circumferential direction between the adjacent two lateral grooves 63. The sipe 652 is formed in two between two adjacent lateral grooves 63 in the tire circumferential direction. The sipes 652 are preferably formed at positions approximately trisecting in the tire circumferential direction between the adjacent two lateral grooves 63.

The second intermediate block 60 is formed with a lateral groove 63 extending from the second center main groove 22 toward the second shoulder main groove 23 at a predetermined inclination angle with respect to the tire axial direction. One end of the lateral groove 63 opens at the second center main groove 22, and the other end of the lateral groove 63 opens at the second shoulder main groove 23. The inclination angle of the lateral groove 63 with respect to the tire axial direction is substantially the same as the knife grooves 651, 652.

The groove width of the lateral groove 63 varies throughout the tire axial direction. Specifically, the groove width of the lateral groove 63 at the portion from the second center main groove 22 to the longitudinal groove 612 is smaller than the groove width of the lateral groove 63 at the portion from the longitudinal groove 612 to the second shoulder main groove 23. The groove width of the lateral groove 63 at the portion from the second center main groove 22 to the longitudinal groove 612 is, for example, 30% to 70% of the groove width of the lateral groove 63 at the portion from the longitudinal groove 612 to the second shoulder main groove 23. By changing the groove width of the lateral groove 63, pumping noise (noise) generated from the lateral groove 63 when the tire is grounded can be reduced.

The second shoulder block 70 has a lateral sipe 72 and a lateral sipe 73 extending outward in the tire axial direction from the second shoulder main groove 23. The lateral sipes 72 and 73 are formed in plural at intervals in the tire circumferential direction. The lateral cutter grooves 72 are formed in two between two adjacent lateral grooves 73. The lateral sipes 72 are preferably formed at positions approximately trisected in the tire circumferential direction between the adjacent two lateral sipes 73. The inclination angles of the lateral sipes 72 and 73 with respect to the tire axial direction are substantially the same, and are, for example, 5 ° to 20 °.

One end of the lateral sipe 72 opens into the first central main groove 21, and the other end of the lateral sipe 72 terminates into the second shoulder block 70. Preferably, the other end of the lateral sipe 72 is located outside the ground contact end E2 with respect to the tire axial direction. One end of the lateral groove 73 opens into the second shoulder main groove 23, and the other end of the lateral groove 73 extends beyond the ground contact end E2 to the vicinity of the side rib 13. By extending the lateral groove 73 to the vicinity of the side rib 13, drainage is improved.

The lateral groove 73 includes a shallow groove portion 731 having a smaller depth than the other portions of the lateral groove 73, and a narrow portion 732 having a smaller groove width than the other portions of the lateral groove 73. The shallow groove portion 731 is formed in the vicinity of the connection position of the lateral groove 73 and the second shoulder main groove 23. The depth of the shallow groove 731 is, for example, 20% to 50% of the depth of the other portion of the horizontal groove 73. The groove wall surface of the shallow groove 731 is preferably inclined so that the groove width becomes narrower as it goes toward the groove bottom. By forming the shallow groove portion 731, the rigidity of the second shoulder block 70 can be improved, and the steering stability can be improved.

The narrow portion 732 is formed on the outer side of the shallow groove portion 731 in the tire axial direction. The groove width of the narrow portion 732 is, for example, 10% to 50% of the other portion of the transverse groove 73. By forming the narrow portion 732, the rigidity of the second shoulder block 70 can be improved, and the steering stability can be improved.

The first shoulder block 30 is described in detail below with reference to fig. 3 to 7. Fig. 3 is a plan view showing the vicinity of the first shoulder block 30, and fig. 4 is a perspective view in which the vicinity of the first shoulder block 30 is enlarged. Fig. 5 to 7 are cross-sectional views taken along line AA, line BB, and line CC in fig. 3, respectively.

As shown in fig. 3 and 4, longitudinal sipes 311 and 312 are formed in the first shoulder block 30 along the tire circumferential direction. In the present embodiment, the groove widths of the longitudinal sipes 311 and 312 are substantially uniform throughout the tire radial direction except in the vicinity of the groove bottom, but the present invention is not limited thereto. For example, the groove wall surfaces of the longitudinal grooves 311, 312 may be inclined so that the groove width becomes narrower as the groove bottom is formed.

A step 37 extending inward in the tire axial direction is formed on the groove wall surface of the longitudinal sipe 311. The steps 37 are formed at predetermined intervals in the tire circumferential direction. The depth of the step 37 is, for example, 10% to 50% of the depth of the longitudinal groove 311. The width of the step 37 in the tire axial direction is substantially uniform throughout the tire circumferential direction, for example, substantially the same as the width of the longitudinal sipe 311. The length of the steps 37 in the tire circumferential direction is not particularly limited, and is, for example, substantially the same as the length of the intervals of the steps 37 in the tire circumferential direction. By providing the step 37 on the groove wall surface of the longitudinal groove 311, the drainage performance of the longitudinal groove 311 is improved. In the present embodiment, the step 37 is formed at a predetermined interval in the tire circumferential direction, but the present invention is not limited thereto. For example, the step 37 may be formed over the entire circumference in the tire circumferential direction.

The first shoulder block 30 has a lateral sipe 32 and a lateral sipe 33 extending outward in the tire axial direction from a longitudinal sipe 311. One ends of the lateral cutter groove 32 and the lateral cutter groove 33 are opened to the longitudinal cutter groove 311, and the other ends of the lateral cutter groove 32 and the lateral cutter groove 33 extend to the vicinity of the side rib 13. The inclination angles of the lateral sipes 32 and 33 with respect to the tire axial direction are substantially the same, and are, for example, 5 ° to 20 °. The groove width of the lateral sipe 32 (excluding the wide portion 321 described later) and the lateral sipe 33 (excluding the wide portion 331 described later) are substantially uniform in the entire tire axial direction. The depth of the lateral sipe 32 (excluding the wide portion 321 described later) and the lateral sipe 33 is not particularly limited, and is, for example, 50% to 150% of the depth of the longitudinal sipe 311.

The lateral cutter groove 32 includes a wide portion 321 having a shallower depth than the other portions of the lateral cutter groove 32 and a wider width than the other portions of the lateral cutter groove 32. The wide portion 321 is formed at a connection position between the lateral sipe 32 and the longitudinal sipe 311. The depth of the wide portion 321 is, for example, 10% to 50% of the depth of the other portion of the lateral sipe 32. The width of the wide portion 321 gradually increases toward the connection position of the lateral sipe 32 and the longitudinal sipe 311. The width of the wide portion 321 at the connection position of the lateral sipe 32 and the longitudinal sipe 311 is, for example, 200 to 500% of the width of the other portion of the lateral sipe 32. By forming the wide portion 321, the rigidity of the first shoulder block 30 can be improved, and the steering stability can be improved.

The transverse groove 33 includes a wide portion 331 having a width wider than other portions of the transverse groove 33. The width of the wide portion 331 becomes gradually larger toward the connection position of the horizontal groove 33 and the vertical sipe 311. The width of the wide portion 331 at the connection position of the horizontal groove 33 and the vertical blade groove 311 is, for example, 110 to 200% of the width of the other portion of the horizontal groove 33. The depth of the wide portion 331 is not particularly limited, but is substantially the same as the depth of the lateral groove 33 in the present embodiment. By forming the wide portion 331, the capacity of the lateral groove 33 can be increased, and the drainage can be improved.

A slope 36 extending obliquely to the first shoulder main groove 20 is formed on the inner side surface in the tire axial direction of the first shoulder block 30. The inclined surface 36 includes a first inclined surface 361 extending along the tire circumferential direction, and a second inclined surface 362 extending in a direction inclined at a predetermined angle with respect to the tire circumferential direction.

As shown in fig. 3, the inclination angle θ ₁ of the second inclined surface 362 with respect to the tire circumferential direction is preferably 1 ° or more, and more preferably 3 ° or more. By setting the inclination angle θ ₁ to 1 ° or more, drainage can be improved. The inclination angle θ ₁ is preferably 30 ° or less, and more preferably 20 ° or less. By setting the inclination angle θ ₁ to 30 ° or less, a decrease in rigidity of the first shoulder block 30 can be suppressed, and steering stability can be ensured. Accordingly, an example of a suitable range of the inclination angle θ ₁ is 1 ° to 30 °, more preferably 3 ° to 20 °.

When the ground contact surface of the tread 10 has a rectangular rate of 0.55 to 0.85, the end of the ground contact surface intersects the second inclined surface 362 at a substantially right angle in a plan view, as will be described in detail later. Accordingly, the second inclined surface 362 contacts the road surface during sudden braking or sudden acceleration to suppress tilting of the block, the ground contact pressure at the block end portion is reduced, and turning performance during turning is improved.

The first shoulder block 30 has a sipe 35 extending from the first shoulder main groove 20 toward the longitudinal sipe 312 at an inclination angle of approximately 45 ° with respect to the tire axial direction. One end of the sipe 35 is open to the first shoulder main groove 20, and the other end of the sipe 35 is open to the longitudinal sipe 312. The groove width and depth of the sipe 35 are substantially uniform throughout the extending direction of the sipe 35.

A step 34 extending outward from the sipe 35 is formed on a groove wall surface on a side close to the second inclined surface 362 of the groove wall surfaces of the sipe 35. The step 34 includes a portion formed along the sipe 35, and a portion formed between the second inclined surface 362 and the first shoulder main groove 20. The width of the portion of the step 34 formed along the sipe 35 (the width in the direction perpendicular to the extending direction of the sipe 35) becomes gradually larger in the extending direction of the sipe 35 as going toward the first shoulder main groove 20. In addition, the width (width in the tire axial direction) of the portion of the step 34 formed between the second inclined surface 362 and the first shoulder main groove 20 gradually becomes smaller as it moves away from the approaching sipe 35 in the tire circumferential direction.

Fig. 5 is a cross-sectional view taken along line AA in fig. 3, and is a cross-sectional view of first ramp 361. As shown in fig. 5, the inclination angle θ ₃₆₁ of the first inclined surface 361 with respect to the contour plane α along the ground contact surface of the tread 10 is preferably 30 ° or more, more preferably 40 ° or more. By setting the inclination angle θ ₃₆₁ to 30 ° or more, the tank volume can be increased, and drainage can be improved. The inclination angle θ ₃₆₁ of the first inclined surface 361 is preferably 60 ° or less, and more preferably 50 ° or less. By setting the inclination angle θ ₃₆₁ to 60 ° or less, a decrease in the block surface area of the first shoulder block 30 that accompanies formation of the first inclined surface 361 can be suppressed, and wear resistance and grip performance can be ensured. Accordingly, an example of a suitable range of the inclination angle θ ₃₆₁ of the first inclined surface 361 is 30 ° to 60 °, more preferably 40 ° to 50 °.

In the present embodiment, the inclination angle θ ₃₆₁ of the first inclined surface 361 (the same applies to the second inclined surface 362) is uniform in the entire tire radial direction, but the present invention is not limited thereto. For example, the first inclined surface 361 may include a plurality of inclined surfaces inclined at different angles with respect to the profile surface α. In addition, for example, the first inclined surface 361 may include a curved inclined surface. In the present embodiment, the inclination angle θ ₃₆₁ of the first inclined surface 361 is uniform in the entire tire circumferential direction, but is not limited thereto. For example, the inclination angle θ ₃₆₁ of the first inclined surface 361 may be increased or decreased as the connection position between the first inclined surface 361 and the second inclined surface 362 is approached.

The depth H ₃₆₁ of the first inclined surface 361 is preferably 10% or more, more preferably 25% or more of the depth H ₂₀ of the first shoulder main groove 20. By setting the depth H ₃₆₁ of the first inclined surface 361 to 10% or more of the depth H ₂₀ of the first shoulder main groove 20, the groove volume can be increased, and the drainage can be improved. The depth H ₃₆₁ of the first inclined surface 361 is preferably 70% or less, more preferably 60% or less of the depth H ₂₀ of the first shoulder main groove 20. By setting the depth H ₃₆₁ of the first inclined surface 361 to 70% or less of the depth H ₂₀ of the first shoulder main groove 20, a decrease in the block volume of the first shoulder block 30 that accompanies formation of the first inclined surface 361 can be suppressed. This suppresses a decrease in the rigidity of the first shoulder block 30 and improves the steering stability. Accordingly, an example of the suitable range of the depth H ₃₆₁ of the first inclined surface 361 is 10% to 70%, more preferably 25% to 60%, with respect to the depth H ₂₀ of the first shoulder main groove 20. The depth H ₃₆₁ of the first inclined surface 361 is the shortest distance from the profile surface α to the deepest portion of the first inclined surface 361.

In the present embodiment, the depth H ₃₆₁ of the first inclined surface 361 (the same applies to the second inclined surface 362) is uniform in the entire tire circumferential direction, but the present invention is not limited thereto. For example, the depth H ₃₆₁ of the first slope 361 may be increased or decreased as the connection position between the first slope 361 and the second slope 362 is approached.

The width W ₃₆₁ of the first inclined surface 361 is preferably 20% or more of the width W ₂₀ of the first shoulder main groove 20, and more preferably 25% or more of the width W ₂₀ of the first shoulder main groove 20. By setting the width W ₃₆₁ of the first inclined surface 361 to 20% or more of the width W ₂₀ of the first shoulder main groove 20, the groove volume can be increased, and the drainage performance can be improved. The width W ₃₆₁ of the first inclined surface 361 is preferably 50% or less of the width W ₂₀ of the first shoulder main groove 20, and more preferably 45% or less of the width W ₂₀ of the first shoulder main groove 20. By setting the width W ₃₆₁ of the first inclined surface 361 to 50% or less of the width W ₂₀ of the first shoulder main groove 20, it is possible to suppress a decrease in the block surface area of the first shoulder block 30 that accompanies formation of the first inclined surface 361, and to ensure wear resistance and grip performance. Accordingly, an example of a suitable range of the width W ₃₆₁ of the first inclined surface 361 is 20% to 50%, more preferably 25% to 45%, with respect to the width W ₂₀ of the first shoulder main groove 20. The width of the first inclined surface is a length in a direction perpendicular to a direction in which the adjacent main groove extends in a plan view. The width of the main groove is the length between the intersection points of the virtual line and the contour surface α, which are obtained by extending the groove walls on both sides toward the contour surface α.

Fig. 6 is a cross-sectional view taken along line BB in fig. 3, and is a cross-sectional view of the second ramp 362. As shown in fig. 6, the inclination angle θ ₃₆₂ of the second inclined surface 362 with respect to the contour surface α may be substantially the same as or different from the inclination angle θ ₃₆₁ (see fig. 5) of the first inclined surface 361. The inclination angle θ ₃₆₂ of the second inclined surface 362 is preferably 30 ° to 60 °, more preferably 40 ° to 50 °, from the same viewpoint as the inclination angle θ ₃₆₁ of the first inclined surface 361.

The depth H ₃₆₂ of the second inclined surface 362 may be substantially the same as or different from the depth H ₃₆₁ (see fig. 5) of the first inclined surface 361. The depth H ₃₆₂ of the second inclined surface 362 is preferably 10% to 70%, more preferably 25% to 60% of the depth H ₂₀ of the first shoulder main groove 20 from the same viewpoint as the depth H ₃₆₁ of the first inclined surface 361. In addition, a step 34 is formed between the second inclined surface 362 and the first shoulder main groove 20. Accordingly, the depth H ₃₆₂ of the second chamfer 362 coincides with the distance from the profile surface α to the step 34.

In the present embodiment, the step 34 is formed substantially parallel to the contour surface α, but the present invention is not limited thereto. For example, a slope extending obliquely to the first shoulder main groove 20 may be formed in the step 34. The inclination angle of the inclined surface formed on the step 34 may be substantially the same as or different from the inclination angle θ ₃₆₂ of the second inclined surface 362. In addition, the inclined surface formed on the step 34 may include a curved inclined surface.

The width of the second inclined surface 362 may be substantially the same as or different from the width W ₃₆₁ (see fig. 5) of the first inclined surface 361. The width of the second inclined surface 362 is preferably 20 to 50%, more preferably 25 to 45% of the width W ₂₀ of the first shoulder main groove 20 from the same viewpoint as the width W ₃₆₁ of the first inclined surface 361. The width of the second inclined surface 362 is a width along a direction perpendicular to the direction in which the second inclined surface 362 extends.

Fig. 7 is a sectional view taken along line CC in fig. 3, and is a sectional view of the sipe 35 and the step 34. The depth H ₃₅ of the sipe 35 is not particularly limited, and may be substantially the same as the depth H ₂₀ (see fig. 5) of the first shoulder main groove 20, or may be 70% to 95% of the depth H ₂₀ of the first shoulder main groove 20. In the present embodiment, the groove wall surface in the vicinity of the groove bottom of the sipe 35 is curved, but not limited thereto. For example, the groove wall surface and the groove bottom surface of the sipe 35 may be connected at substantially right angles. In the present embodiment, the sipe 35 has a substantially uniform groove width in the tire radial direction, but the present invention is not limited thereto. For example, the groove width of the sipe 35 may be formed so as to be narrower as the groove bottom is approached. Further, a slope having a predetermined inclination angle with respect to the contour surface α may be formed on the groove wall surface of the sipe 35.

The first intermediate block 40 is described in detail below with reference to fig. 8 to 12. Fig. 8 is a plan view showing the vicinity of the first intermediate block 40, and fig. 9 is a perspective view in which the vicinity of the first intermediate block 40 is enlarged. Fig. 10 to 12 are cross-sectional views taken along line DD, line EE, and line FF in fig. 8, respectively.

Three longitudinal sipes 411, 412, 413 are formed in the first intermediate block 40 along the tire circumferential direction. In the present embodiment, the groove widths of the longitudinal cutter grooves 411, 412, 413 are substantially uniform in the tire radial direction except in the vicinity of the groove bottom, but the present invention is not limited thereto. For example, the groove wall surfaces of the longitudinal tool grooves 411, 412, 413 may be inclined so that the groove width becomes narrower as the groove bottom is formed.

The longitudinal sipe 412 has a plurality of widened portions 412A having an enlarged groove width. The maximum groove width of the widened portion 412A is not particularly limited, and is, for example, 200 to 500% of the width of the other portion of the longitudinal groove 412. By forming the widened portion 412A, the heat accumulated in the tire axial direction center of the first intermediate block 40 can be cooled. In the present embodiment, the groove wall surface of the widened portion 412A is formed in an arcuate shape, but is not limited thereto. For example, the shape of コ may be also be a waveform.

A slope 46 extending obliquely to the first shoulder main groove 20 is formed on the tire axial direction outer side surface of the first intermediate block 40. The inclined surface 46 includes a first inclined surface 461 extending along the tire circumferential direction, and a second inclined surface 462 extending in a direction inclined at a prescribed angle with respect to the tire circumferential direction. Further, a slope 47 extending obliquely toward the first center main groove 21 is formed on the inner side surface in the tire axial direction of the first intermediate block 40. The inclined surface 47 includes a first inclined surface 471 extending along the tire circumferential direction and a second inclined surface 472 extending in a direction inclined at a predetermined angle with respect to the tire circumferential direction, similarly to the inclined surface 46.

As shown in fig. 8, the inclination angle θ ₂ of the second inclined surface 462 with respect to the tire circumferential direction and the inclination angle θ ₃ of the second inclined surface 472 with respect to the tire circumferential direction may be different from the inclination angle θ ₁ (see fig. 3), but are preferably substantially the same as the inclination angle θ ₁ (see fig. 3). From the same viewpoint as the inclination angle θ ₁, an example of a suitable range of the inclination angle θ ₂、θ₃ is 1 ° to 30 °, and more preferably 3 ° to 20 °.

When the ground contact surface of the tread 10 has a rectangle ratio of 0.55 to 0.85, the end of the ground contact surface intersects the second inclined surfaces 462, 472 at a substantially right angle in a plan view, which will be described in detail later. Accordingly, the second inclined surfaces 462 and 472 contact the road surface during sudden braking and sudden acceleration to suppress tilting of the blocks, and the ground contact pressure at the block ends is reduced, thereby improving the steering stability during normal running.

The first intermediate block 40 has a sipe 451 extending from the first shoulder main groove 20 toward the longitudinal sipe 411 at an inclination angle of approximately 45 ° with respect to the tire axial direction. One end of the blade groove 451 opens into the first shoulder main groove 20, and the other end of the blade groove 451 opens into the longitudinal blade groove 411. Further, the first intermediate block 40 is formed with a sipe 452 extending from the first center main groove 21 toward the longitudinal sipe 413 at an inclination angle of approximately 45 ° with respect to the tire axial direction. One end of the sipe 452 opens into the first center main groove 21, and the other end of the sipe 452 opens into the longitudinal sipe 413. The groove width and depth of the sipes 451, 452 are substantially uniform throughout the extending direction of the sipes 451, 452.

Of the groove wall surfaces of the tool grooves 451, 452, the groove wall surfaces on the side close to the second inclined surfaces 462, 472 are respectively formed with steps 441, 442 extending outward. The step 441 includes a portion formed along the sipe 451, and a portion formed between the second inclined surface 462 and the first shoulder main groove 20. In addition, the step 442 includes a portion formed along the pocket 452, and a portion formed between the second inclined surface 472 and the first central main groove 21.

The width of the portion of the step 441 formed along the sipe 451 (the width in the direction perpendicular to the extending direction of the sipe 451) becomes gradually larger in the extending direction of the sipe 451 as going toward the first shoulder main groove 20. In addition, the width of the portion of the step 441 formed between the second inclined surface 462 and the first shoulder main groove 20 (the width in the tire axial direction) gradually becomes larger in the tire circumferential direction as it goes away from the connection position of the first inclined surface 461 and the second inclined surface 462.

As for the step 442, as well as the step 441, the width of the portion of the step 442 formed along the sipe 452 (the width in the direction perpendicular to the extending direction of the sipe 452) gradually becomes larger in the extending direction of the sipe 452 as going toward the first center main groove 21. In addition, the width of the portion of the step 442 formed between the second inclined surface 472 and the first center main groove 21 (the width in the tire axial direction) gradually becomes larger in the tire circumferential direction as it goes away from the connection position of the first inclined surface 471 and the second inclined surface 472.

The cross-sectional shapes of the first inclined surface 461, the second inclined surface 462, and the sipe 451 will be described below with reference to fig. 10to 12. The first inclined surface 471, the second inclined surface 472, and the pocket 452 are not described, but may be the same. Fig. 10 is a cross-sectional view taken along line DD in fig. 8, and is a cross-sectional view of the first ramp 461. The inclination angle θ ₄₆₁ of the first inclined surface 461 with respect to the contour plane α along the ground contact surface of the tread 10 may be different from the inclination angle θ ₃₆₁ of the first inclined surface 361 formed in the first shoulder block 30 with respect to the contour plane α, but is preferably substantially the same. From the same viewpoint as the inclination angle θ ₃₆₁, an example of a suitable range of the inclination angle θ ₄₆₁ of the first inclined surface 461 is 30 ° to 60 °, and more preferably 40 ° to 50 °.

In the present embodiment, the inclination angle θ ₄₆₁ of the first inclined surface 461 (the same applies to the second inclined surface 462) is uniform in the entire tire radial direction, but the present invention is not limited thereto. For example, the first inclined surface 461 may include a plurality of inclined surfaces inclined at different angles with respect to the contour surface α. In addition, for example, the first inclined surface 461 may also include a curved inclined surface. In the present embodiment, the inclination angle θ ₄₆₁ of the first inclined surface 461 is uniform in the entire tire circumferential direction, but is not limited thereto. For example, the inclination angle θ ₄₆₁ of the first inclined surface 461 may be increased or decreased as the connection position of the first inclined surface 461 and the second inclined surface 462 is approached.

The depth H ₄₆₁ of the first inclined surface 461 may be different from the depth H ₃₆₁ of the first inclined surface 361 formed in the first shoulder block 30, but is preferably substantially the same. From the same viewpoint as the depth H ₃₆₁ of the first inclined surface 361, an example of the suitable range of the depth H ₄₆₁ of the first inclined surface 461 is preferably 10% to 70%, more preferably 25% to 60%, with respect to the depth H ₂₀ of the first shoulder main groove 20.

In the present embodiment, the depth H ₄₆₁ of the first inclined surface 461 (the same applies to the second inclined surface 462) is uniform in the entire tire circumferential direction, but is not limited thereto. For example, the depth H ₄₆₁ of the first slope 461 may be increased or decreased as the connection position of the first slope 461 and the second slope 462 is approached.

The width W ₄₆₁ of the first inclined surface 461 may be different from the width W ₃₆₁ of the first inclined surface 361 formed in the first shoulder block 30, but is preferably substantially the same. From the same viewpoint as the width W ₃₆₁ of the first inclined surface 361, an example of a suitable range of the width W ₄₆₁ of the first inclined surface 461 is preferably 20% to 50%, more preferably 25% to 45%, with respect to the width W ₂₀ of the first shoulder main groove 20.

Fig. 11 is a sectional view taken along line CC in fig. 8, and is a sectional view of the second ramp 462. As shown in fig. 11, the inclination angle θ ₄₆₂ of the second inclined surface 462 with respect to the contour surface α may be substantially the same as or different from the inclination angle θ ₄₆₁ (see fig. 10) of the first inclined surface 461. The inclination angle θ ₄₆₂ of the second inclined surface 462 is preferably 30 ° to 60 °, more preferably 40 ° to 50 °, from the same viewpoint as the inclination angle θ ₄₆₁ of the first inclined surface 461.

The depth H ₄₆₂ of the second inclined surface 462 may be substantially the same as or different from the depth H ₄₆₁ (see fig. 10) of the first inclined surface 461. The depth H ₄₆₂ of the second inclined surface 462 is preferably 10% to 70%, more preferably 25% to 60% of the depth H ₂₀ of the first shoulder main groove 20 from the same viewpoint as the depth H ₄₆₁ of the first inclined surface 461. In addition, a step 441 is formed between the second inclined surface 462 and the first shoulder main groove 20. Accordingly, the depth H ₄₆₂ of the second slope 462 coincides with the distance from the contour plane α to the step 441.

In the present embodiment, the step 441 is formed substantially parallel to the contour surface α, but is not limited thereto. For example, the step 441 may be formed with a slope extending obliquely to the first shoulder main groove 20. The inclination angle of the inclined surface formed on the step 441 may be substantially the same as or different from the inclination angle θ ₄₆₂ of the second inclined surface 462. In addition, the inclined surface formed at the step 441 may include a curved inclined surface.

The width of the second inclined surface 462 may be substantially the same as or different from the width W ₄₆₁ (see fig. 10) of the first inclined surface 461. The width of the second inclined surface 462 is preferably 20 to 50%, more preferably 25 to 45% of the width W ₂₀ of the first shoulder main groove 20, from the same viewpoint as the width W ₄₆₁ of the first inclined surface 461. The width of the second inclined surface 462 refers to a width along a direction perpendicular to a direction in which the second inclined surface 462 extends.

Fig. 12 is a sectional view taken along line CC in fig. 8, and is a sectional view of the pocket 451 and the step 441. The depth H ₄₅₁ of the sipe 451 is not particularly limited, and may be substantially the same as the depth H ₂₀ of the first shoulder main groove 20, or may be 70% to 95% of the depth H ₂₀ of the first shoulder main groove 20. In the present embodiment, the groove wall surface near the groove bottom of the sipe 451 is curved, but not limited thereto. For example, the groove wall surface and the groove bottom surface of the sipe 451 may be connected at substantially right angles. In the present embodiment, the sipe 451 has a substantially uniform groove width in the tire radial direction, but the present invention is not limited thereto. For example, the groove width of the sipe 451 may be inclined so as to be narrower as the groove bottom is inclined. Further, a slope having a predetermined inclination angle with respect to the contour surface α may be formed on the groove wall surface of the pocket 451.

The shape of the ground contact surface of the tread 10 will be described in detail below with reference to fig. 13 and 14. Fig. 13 is a diagram schematically showing the shape of the ground contact surface of the tread 10, fig. 14 is a perspective view of the pneumatic tire 1, and is an enlarged view showing the outside of the vehicle.

As shown in fig. 13, the ground contact length (L2) near the ground contact end is short with respect to the ground contact length (L1) along the tire circumferential direction of the ground contact surface on the equator CL, and the ground contact surface of the tread 10 has a shape similar to an elliptical shape. Here, the ground contact length (L1) is a length along the tire circumferential direction on the equator CL of the ground contact surface when a load corresponding to 70.4% of the normal load is applied in a state where the unused pneumatic tire is mounted on the normal rim and filled with air so as to have a predetermined internal pressure. The ground contact length (L2) is the length of the ground contact surface along the tire circumferential direction at a position 10mm inward in the tire axial direction from both ends of the ground contact surface in the tire axial direction obtained by the above measurement conditions. The predetermined internal pressure under the above measurement conditions was 200kPa when the tire flatness ratio was 60% or more, and was 220kPa when the tire flatness ratio was less than 60%. In the tire described as Extra Load, the predetermined internal pressure under the above measurement conditions is 240kPa when the flattening ratio is 60% or more, and is 260kPa when the flattening ratio is less than 60%.

In this specification, L2/L1 is defined as the rectangle rate of the ground contact surface of the tread 10. In the present embodiment, the ground contact length (L2) is substantially the same length on the left and right sides of the tread 10.

The ground contact surface of the tread 10 has a rectangle ratio of 0.55 to 0.85. In the tread pattern of the present embodiment, when the rectangle ratio under the above conditions is 0.55 to 0.85, the end portion of the ground contact surface intersects with the second inclined surface 362 formed in the first shoulder block 30 at a substantially right angle in a plan view as shown in fig. 13. This improves the drainage property toward the outer side in the tire axial direction. In addition, during sudden braking and sudden acceleration, the second inclined surface 362 contacts the road surface, so that the ground contact pressure at the block end is reduced, the ground contact surface is suppressed from floating, and the cornering performance during cornering is improved.

The rectangular rate of the ground plane is more preferably 0.60 to 0.80, still more preferably 0.65 to 0.75, and particularly preferably 0.68 to 0.72. In the tread pattern of the present embodiment, when the rectangular rate of the ground contact surface is less than 0.55, the steering stability is lowered, and it is difficult to combine both good drainage and excellent steering stability. On the other hand, when the rectangular rate of the ground plane exceeds 0.85, the drainage property is lowered, and in this case, it is difficult to combine both good drainage property and excellent steering stability.

The belt reinforcement 17 and the belt angle according to the present embodiment will be described below as a mode for setting the rectangle ratio of the ground contact surface to 0.55 to 0.85.

First, the belt reinforcement 17 is explained. As shown in fig. 14, the belt reinforcement 17 is disposed between the belt 16 and the tread 10. The belt reinforcement 17 is disposed for the purpose of improving durability, reducing road noise during running, and the like. The belt reinforcement 17 has, for example, a two-layer construction including a cap ply 18 and an edge ply 19. The structure of the belt reinforcing member 17 is not limited to this. For example, the cap ply 18 may be omitted, or the edge ply 19 may be provided with two layers.

The cap ply layer 18 is disposed between the left and right side ribs 13 so as to extend in the tire axial direction. The cap ply 18 is made of an insulating organic fiber layer such as polyamide fiber, and is covered with a top layer rubber.

The edge ply 19 is disposed at each end of the belt layer 16 in the tire axial direction. Preferably, as shown in fig. 14, the inner end 19A of the edge ply 19 is located further outside than the outer end 362A of the second inclined surface 362 formed on the first shoulder block 30 in the tire axial direction. Thus, the rectangular rate of the ground plane can be easily set to 0.55 to 0.85. The inner end 19A is an end of the edge ply 19 located at the innermost side in the tire axial direction. The outer end 362A of the second inclined surface 362 is the outermost position in the tire axial direction at the intersection of the second inclined surface 362 and the contour surface α along the ground contact surface of the tread 10.

The belt angle is explained next. The belt angle is an angle of the belt cord with respect to the tire circumferential direction. The belt angle is preferably 21 ° to 27 °. If the ratio is within this range, the rectangular rate of the ground plane is easily set to 0.55 to 0.85. When the belt angle is smaller than 21 °, the restraining force of the belt 16 becomes strong, resulting in a rectangle ratio of the ground contact surface exceeding 0.85. On the other hand, when the belt angle is larger than 27 °, the restraining force of the belt 16 becomes weak, resulting in the rectangle ratio of the ground contact surface becoming smaller than 0.55. The belt angle is more preferably 22 ° to 26 °, still more preferably 23 ° to 25 °.

As described above, according to the pneumatic tire 1 having the above-described structure, excellent steering stability can be achieved while ensuring good drainage. By forming the second inclined surface 362 extending obliquely to the first shoulder main groove 20 and extending in a direction inclined at a predetermined angle with respect to the tire circumferential direction on the inner side surface in the tire axial direction of the first shoulder block 30, and setting the rectangular rate of the ground contact surface of the tread 10 to 0.55 to 0.85, the second inclined surface 362 contacts the road surface during sudden braking and sudden acceleration, the ground contact pressure of the block end portion is reduced, the floating of the ground contact surface is suppressed, and the cornering performance at cornering is improved.

The above-described embodiments can be appropriately modified within a range that does not impair the object of the present invention. In the above-described embodiment, the first inclined surface extending in the tire circumferential direction and the second inclined surface extending in the direction inclined at a predetermined angle with respect to the tire circumferential direction are formed, but for example, the first inclined surface may not be formed. In the above embodiment, the step is formed between the second inclined surface and the main groove, but for example, the step may not be formed. The number, shape, etc. of the lateral grooves and sipes formed in each block may be changed within a range that does not impair the object of the present invention.

Claims

1. A pneumatic tire having a tread, wherein the assembly direction of the pneumatic tire with respect to a vehicle is specified,

The tread has:

a first shoulder main groove extending along the tire circumferential direction; and

A first shoulder block divided by the first shoulder main groove and disposed on the vehicle outside,

A slope extending obliquely to the first shoulder main groove side adjacent to the first shoulder block is formed on a side surface of the first shoulder block on the inner side in the tire axial direction,

The inclined surface extends in a direction inclined at a prescribed angle with respect to the tire circumferential direction,

The rectangle rate of the ground contact surface of the tread is 0.55-0.85.

2. The pneumatic tire of claim 1, wherein,

The width of the inclined plane is more than 20% of the width of the adjacent first shoulder main groove.

3. The pneumatic tire of claim 1 or 2, wherein,

The pneumatic tire further includes:

A belt layer; and

An edge ply provided at an end portion of the belt layer in the tire axial direction and disposed outside the vehicle,

The inner end of the edge ply in the tire axial direction is arranged at a position outside the outer end of the inclined surface in the tire axial direction.

4. The pneumatic tire of claim 1 or 2, wherein,

The pneumatic tire is further provided with a belt layer,

The belt angle of the belt layer is 21-27 degrees.