JP2024014473A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that can increase degrees of freedom for an adjustment range of PRCF and effectively suppress PRCF.

SOLUTION: A plurality of lands 50 of a tread 30 include a pair of shoulder lands 51 and 52 and central lands 53 and 54. The shoulder lands 51 and 52 are extended in a direction crossing a tire circumferential direction and arranged at an interval in the tire circumferential direction, at least portions of which have a plurality of inclined grooves 51a and 52a arranged in a grounding-width area 39. A carcass ply 70 has a ply main body part 70A, and a pair of ply folded-back parts 70B folded back at a bead core 11 from the ply main body part 70A and extended up to the shoulder lands 51 and 52 to overlap in a tire radial direction with a belt 31. An inclination direction with respect to the tire circumferential direction of ply cords 70d of the ply main body part 70A is the opposite direction of the inclination direction with respect to the tire circumferential direction of the inclined grooves 51a and 52a in the grounding-width area 39.

SELECTED DRAWING: Figure 3

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to pneumatic tires.

In vehicles such as four-wheeled cars, it is considered normal for the vehicle to travel straight due to SAT (Self Aligning Torque) when the steering wheel is released, but the vehicle exhibits a tendency to gradually deviate from straight ahead. There are cases. This vehicle deflection is caused by tire characteristics, and is caused by the effects of CRCF (Conicity Residual Cornering Force) and PRCF (Ply steer Residual Cornering Force). CRCF is a force that is generated when a lateral force is generated on a tire due to a change in shape, such as a difference in thickness between the left and right sides of one tire. On the other hand, PRCF is a force generated by the direction of the cord of the belt buried near the surface layer of the tire tread (angle of inclination to the tire circumferential direction) and the tread pattern, and can be adjusted by design. . For example, in Patent Document 1, narrow grooves are formed on the tread surface of the ribs/blocks of the tread so that the reaction force generated by the narrow grooves acts in a direction that cancels out the deflection force generated by the inclination of the belt in the cord direction. , a pneumatic tire is shown that is inclined with respect to the groove depth direction.

Japanese Patent Application Publication No. 2005-335646

When adjusting the PRCF, if the tread pattern is changed as in Patent Document 1, the mold for molding the tire must be changed, but the tread pattern must be adjusted again after the mold has been determined. It is difficult. On the other hand, although it is possible to adjust the PRCF by changing the inclination angle of the belt cord, the range of adjustment is limited because the inclination angle of the belt cord is also a factor that determines the performance of the tire itself.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire that can increase the degree of freedom in adjusting the PRCF range and can effectively suppress PRCF. It is said that

The pneumatic tire of the present invention includes a pair of beads having a bead core, a pair of sidewalls extending outward in the tire radial direction from each of the pair of beads, and a pair of sidewalls arranged between the pair of sidewalls, and having a predetermined ground contact width. A pneumatic tire comprising: a tread having a tread surface including a region and in which a belt having a plurality of belt cords is embedded; and a carcass ply disposed between the pair of beads and having a plurality of ply cords. The tread includes a plurality of lands arranged along the tire circumferential direction, and a plurality of main grooves arranged between the plurality of lands in the tire axial direction and extending in the tire circumferential direction, The plurality of lands includes a pair of shoulder lands respectively arranged at both ends in the tire axial direction, and at least one center land arranged between the pair of shoulder lands in the tire axial direction, Each of the shoulder lands has a plurality of inclined grooves that extend in a direction intersecting the tire circumferential direction, are arranged at intervals in the tire circumferential direction, and at least a part of which is arranged in the ground contact width region. The carcass ply has a ply main body disposed between the pair of beads, and is folded back from the ply main body at the bead core of the pair of beads, and the folded end extends to the shoulder land and a pair of ply folded parts that overlap with the belt in the tire radial direction, and the inclination direction of the ply cord with respect to the tire circumferential direction in the ply main body part disposed on the tread is the same as that of the inclination groove in the ground contact width region. This is the opposite direction to the direction of inclination with respect to the tire circumferential direction.

According to the present invention, it is possible to provide a pneumatic tire that can increase the degree of freedom in adjusting the PRCF and can effectively suppress PRCF.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the half cross section of the tire axial direction of the pneumatic tire based on embodiment. It is a front view showing a part of tread of the pneumatic tire concerning an embodiment. FIG. 2 is a developed view schematically showing the structure of a carcass ply and a belt according to an embodiment. FIG. 3 is a diagram showing the respective inclination angles of the ply cord of the carcass ply and the first inclined groove with respect to the tire circumferential direction. FIG. 6 is a diagram showing the respective inclination angles of the ply cord of the carcass ply and the second inclined groove with respect to the tire circumferential direction.

Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 shows a cross section of a tire 1, which is a pneumatic tire according to an embodiment, in the tire axial direction. FIG. 2 is a front view showing a part of the tread surface 37 of the tire 1.

The cross-sectional view of FIG. 1 is an axial cross-sectional view (tire meridian cross-sectional view) of the tire 1 in an unloaded state when the tire 1 is mounted on a regular rim (not shown) and filled with a regular internal pressure. A regular rim is a rim defined for each tire by the standard in a standard system including the standard on which the tire is based, for example, a standard rim for JATMA, and a "Measuring Rim" for TRA and ETRTO. Regular internal pressure is the air pressure specified for each tire by each standard in the standard system including the standard on which the tire is based.For truck bus tires and light truck tires, the maximum air pressure is JATMA, For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and for ETRTO, it is "INFLATION PRESSURE". For passenger car tires, the pressure is normally 180kPa, but for tires marked with "Extra Load" or "Reinforced", the pressure is 220kPa.

The basic structure of the tire 1 is symmetrical in cross section in the tire axial direction. FIG. 1 shows a half section of the right half of the tire 1, and the left half (not shown) has the same structure. In FIG. 1, the symbol S1 is the tire equatorial plane. The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis and located at the center in the tire axial direction.

Here, the tire axial direction is a direction parallel to the tire rotation axis, and is a left-right direction in the paper plane of FIG. In FIG. 1, the tire axial direction is shown as X. The inner side in the tire axial direction is the direction approaching the tire equatorial plane S1, and is the left side in the drawing in FIG. The outer side in the tire axial direction is a direction away from the tire equatorial plane S1, and is on the right side of the paper in FIG.

Further, the tire radial direction is a direction perpendicular to the tire rotation axis, and is a vertical direction in the plane of the paper in FIG. In FIG. 1, the tire radial direction Y is shown. The outer side in the tire radial direction is the direction away from the tire rotation axis, and is the upper side of the paper in FIG. The inner side in the tire radial direction is the direction approaching the tire rotation axis, and in FIG. 1 is the lower side of the page.

As shown in FIG. 1, the tire 1 includes a pair of beads 10, a pair of sidewalls 20 extending outward in the tire radial direction from each of the pair of beads 10, and a tread 30 disposed between the pair of sidewalls 20. , a carcass ply 70 disposed across the pair of beads 10, and an inner liner 80 disposed on the tire inner cavity side of the carcass ply 70.

The pair of beads 10 are arranged on both sides in the tire axial direction and at the inner end in the tire radial direction. The bead 10 includes a bead core 11, a bead filler 12 extending outward in the tire radial direction from the bead core 11, a Chehar 13, and a rim strip rubber 14.

The bead core 11 is an annular member in which a metal bead wire coated with rubber is wound multiple times in the circumferential direction of the tire. The bead core 11 is a member that serves to fix the tire 1 filled with air to the rim. The bead filler 12 has a tapered shape whose thickness decreases as it extends from the inside in the tire radial direction to the outside in the tire radial direction. The bead filler 12 is provided to increase the rigidity of the peripheral portion of the bead 10 and ensure high maneuverability and stability. The bead filler 12 is made of, for example, rubber that is harder than the surrounding rubber members. The inner surface of the bead filler 12 in the tire radial direction is bonded to the outer surface of the bead core 11 in the tire radial direction using, for example, an adhesive.

Chehar 13 further surrounds the outside of carcass ply 70 that surrounds bead core 11 and bead filler 12. The rim strip rubber 14 is arranged on the outer side of the Chehar 13 and the carcass ply 70 in the tire axial direction. Chehar 13 and rim strip rubber 14 contact the inner surface of the rim on which tire 1 is mounted. A rim line 14a along the tire circumferential direction is formed on the outer surface of the rim strip rubber 14 on the outside in the tire axial direction.

The sidewall 20 includes sidewall rubber 21 disposed on the outer side of the carcass ply 70 in the tire axial direction. The sidewall rubber 21 constitutes the outer side surface of the tire 1 in the tire circumferential direction. The tire radially inner end 21c of the sidewall rubber 21 covers the tire radially outer end 14b of the rim strip rubber 14. The sidewall rubber 21 is the part that bends the most when the tire 1 acts as a cushion, and is usually made of flexible rubber with fatigue resistance.

The tread 30 includes an endless belt 31, a cap ply 35, and tread rubber 36. The belt 31 is arranged on the outside of the carcass ply 70 in the tire radial direction. The cap ply 35 is arranged on the outer side of the belt 31 in the tire radial direction. The tread rubber 36 is arranged on the outer side of the cap ply 35 in the tire radial direction. Note that there may be two cap plies 35. Alternatively, a configuration without the cap ply 35 may be used. When the cap ply 35 is not provided, an edge ply may be arranged to press the end of the belt 31 in the tire axial direction from the tire outer surface side. The number of edge plies may be one or two.

The belt 31 is a member that reinforces the tread 30. The belt 31 of the embodiment has a two-layer structure including an inner belt 32 disposed on the outer side of the inner liner 80 in the tire radial direction, and an outer belt 33 disposed on the outer side of the inner belt 32 in the tire radial direction. Both the inner belt 32 and the outer belt 33 have a structure in which belt cords such as a plurality of steel cords are covered with rubber.

The inner belt 32 is wider than the outer belt 33. Therefore, the outer end 32a of the inner belt 32 in the tire axial direction is located on the outer side in the tire axial direction than the outer end 33a of the outer belt 33 in the tire axial direction. By providing the belt 31, the rigidity of the tire 1 is ensured, and the ground contact of the tread 30 with respect to the road surface is improved. Note that the belt 31 is not limited to a two-layer structure, but may have a one-layer, three or more layer structure. The belt 31 has a characteristic configuration in the present disclosure, which will be described in detail later.

The cap ply 35 is a member that reinforces the tread 30 together with the belt 31. The cap ply 35 has a structure in which a plurality of insulating organic fiber cords such as polyamide fibers are covered with rubber, for example. The outer end 35a of the cap ply 35 in the tire axial direction is located further outward in the tire axial direction than the outer end 32a of the inner belt 32 in the tire axial direction. The cap ply 35 covers the entire belt 31 from the tire outer surface side. Although the cap ply 35 in the embodiment has one layer, it may have a structure of two or more layers. By providing the cap ply 35, it is possible to improve durability and reduce road noise during driving.

The tread rubber 36 is arranged on the outer side of the cap ply 35 in the tire radial direction. The tread rubber 36 is a member that constitutes a tread surface 37 that is the outer surface of the tread 30. The axially outer end 36b of the tread rubber 36 curves inward in the tire radial direction beyond the axially outer end 35a of the cap ply 35, and covers the tire radially outer end 21b of the sidewall rubber 21.

A tread pattern 38 is provided on the tread surface 37. The tread pattern 38 will be described with reference to FIG. 2. Note that FIG. 2 shows the tire axial direction X and the tire circumferential direction C.

The tread pattern 38 includes a plurality of lands 50 arranged to extend in the tire circumferential direction, and a plurality of main grooves 60 arranged between the lands 50 in the tire axial direction. The plurality of lands 50 and the plurality of main grooves 60 that constitute the tread pattern 38 both extend annularly along the tire circumferential direction. The tread pattern 38 of the embodiment is a pattern that approximates a so-called symmetrical pattern of a tire.

The tread surface 37 has a ground contact width region 39 that is a region that actually contacts the road surface during running. The ground contact width region 39 is a region between the ground contact ends at both ends of the tire in the axial direction, that is, the first ground contact end 39A on the left side and the second ground contact end 39B on the right side in FIG. In the tread surface 37, a region outside the first ground contact edge 39A and the second ground contact edge 39B in the tire axial direction does not normally contact the road surface. Here, a portion of the tread rubber 36 on the outside in the tire axial direction from each of the first ground contact end 39A and the second ground contact end 39B to the tire axial direction outside end 36b (see FIG. 1) is It's called 40. The shoulder 40 is a portion that transitions from the sidewall 20 to the ground contact width region 39.

Here, the contact edge refers to the axial end of the contact patch when a pneumatic tire mounted on a regular rim and filled with the regular internal pressure is in contact with the ground and a regular load is applied to it. . The regular load is the load specified for each tire by each standard in the standard system including the standard on which the tire is based, and in the case of JATMA it is the "maximum load capacity", and in the case of TRA it is the load specified in the table "TIRE LOAD LIMITS AT". The maximum value listed in "VARIOUS COLD INFLATION PRESSURES" is "LOAD CAPACITY" for ETRTO. When the tire is for a passenger car, the load corresponds to 88% of the above load. If the tires are for racing carts, the normal load is 392N.

The lands 50 of the embodiment include a first shoulder land 51 and a second shoulder land 52 arranged in a left and right pair at both ends in the tire axial direction, and a first shoulder land 51 and a second shoulder land 52. It includes a first center land 53 and a second center land 54 arranged in a left and right pair therebetween. Each land in the embodiment is formed into a rib shape that is continuous in the tire circumferential direction. Note that the first shoulder land 51 and the second shoulder land 52 are an example of a pair of left and right shoulder lands arranged at both ends in the tire axial direction. Further, the first center land 53 and the second center land 54 are examples of center lands arranged between the first shoulder land 51 and the second shoulder land 52 in the tire axial direction.

The main groove 60 of the embodiment includes a central main groove 61 between the first central land 53 and the second central land 54 and a first central groove between the first shoulder land 51 and the first central land 53. , and a second intermediate main groove 63 between the second shoulder land 52 and the second central land 54 . The center main groove 61 is arranged at a position where the equator S2 of the tire 1 passes through the center in the tire axial direction. The first intermediate main groove 62 and the second intermediate main groove 63 are both main grooves located on the outermost side in the tire axial direction. The central main groove 61 and each intermediate main groove 62, 63 are grooves that are continuous in the tire circumferential direction.

The width (tire axial direction dimension) of the first shoulder land 51 and the second shoulder land 52 is approximately the same, and the width of the half width area of the tread surface 37 (the left and right width areas on the outer side in the tire axial direction from the equator S2) is approximately the same. For example, it has a width of about 50% or more and 80% or less.

The first shoulder land 51 has, as the tread pattern 38, a plurality of first inclined grooves 51a having a direction component in the tire axial direction, and a plurality of first sipes 51b. The second shoulder land 52 includes, as the tread pattern 38, a plurality of second inclined grooves 52a having a direction component in the tire axial direction, a plurality of second sipes 52b, and a plurality of third sipes 52c. have. Note that the first slanted groove 51a and the second slanted groove 52a in the embodiment both have a groove width of more than 1 mm. The first sipe 51b, the second sipe 52b, and the third sipe 52c in the embodiment are all grooves with a groove width of 1 mm or less. These inclined grooves 51a, 52a and sipes 51b, 52b, 52c all extend in a direction intersecting the tire circumferential direction. Note that the first inclined groove 51a and the second inclined groove 52a are both examples of inclined grooves arranged in the ground contact width region 39.

The plurality of first inclined grooves 51a of the first shoulder land 51 are arranged at intervals in the tire circumferential direction. The plurality of first inclined grooves 51a are arranged, for example, at a variable pitch in the tire circumferential direction. The first inclined groove 51a has an arcuate shape that is gently convex on one side (lower side in FIG. 2) in the tire circumferential direction. The inner end of the first inclined groove 51a in the tire axial direction does not reach the first intermediate main groove 62, but is terminated. On the other hand, the outer end in the tire axial direction of the first inclined groove 51a extends to the shoulder 40 on the first shoulder land 51 side and is open to the outer surface of the shoulder 40.

The plurality of second inclined grooves 52a of the second shoulder land 52 are arranged at intervals in the tire circumferential direction. The plurality of second inclined grooves 52a are arranged, for example, at a variable pitch in the tire circumferential direction. The second inclined groove 52a has an arcuate shape that is gently convex toward the tire circumferential direction side (upper side in FIG. 2) opposite to the first inclined groove 51a. The inner end of the second inclined groove 52a in the tire axial direction does not reach the second intermediate main groove 63, but is terminated. On the other hand, the outer end in the tire axial direction of the second inclined groove 52a extends to the shoulder 40 on the second shoulder land 52 side and is open to the outer surface of the shoulder 40.

The first inclined groove 51a and the second inclined groove 52a have the same arcuate shape, although their convex directions are different from each other, and are arranged point-symmetrically with respect to each other in FIG. The first inclined groove 51a is arranged slightly outside the center in the axial direction of the tire so that the first ground contact end 39A passes therethrough. The second inclined groove 52a is arranged slightly outside the center in the axial direction of the tire so that the second ground contact end 39B passes therethrough.

Approximately half of each of the first inclined groove 51a and the second inclined groove 52a on the inner side in the tire axial direction extends in the ground contact width region 39. In the ground contact width region 39, the first inclined groove 51a and the second inclined groove 52a extend in the same direction and are substantially parallel to each other. The extending direction of these inclined grooves 51a and 52a in the ground contact width region 39 (indicated by a straight line G in FIG. 2) intersects the tire circumferential direction at an angle θ3. This angle θ3 is an acute angle between the straight line G and the tire circumferential direction. For example, this angle θ3 is approximately 65°, but is not limited to this.

Each of the plurality of first sipes 51b formed on the first shoulder land 51 is arranged approximately at the center between a pair of first inclined grooves 51a adjacent to each other in the tire circumferential direction. These first sipes 51b have a shape that follows the circumferentially adjacent first inclined groove 51a of the tire, and have an arcuate shape that is gently convex downward in FIG. 2. The inner end of the first sipe 51b in the tire axial direction reaches the outer end edge 62a of the first intermediate main groove 62 in the tire axial direction and is open. On the other hand, the outer end of the first sipe 51b in the tire axial direction is located slightly outward in the tire axial direction than the first ground contact end 39A. The first sipe 51b is generally inclined so as to extend upward in FIG. 2 as it goes inward in the tire axial direction.

Each of the plurality of second sipes 52b formed on the second shoulder land 52 is arranged approximately at the center between a pair of second inclined grooves 52a adjacent to each other in the tire circumferential direction. These second sipes 52b have a shape that follows the second inclined groove 52a adjacent in the tire circumferential direction, and are gentle on the tire circumferential side (upper side in FIG. 2) opposite to the first sipe 51b. It has a circular arc shape with a convex shape. The inner end of the second sipe 52b in the tire axial direction reaches the outer end edge 63a of the second intermediate main groove 63 in the tire axial direction and is open. On the other hand, the outer end of the second sipe 52b in the tire axial direction is located slightly on the outer side in the tire axial direction than the second ground contact end 39B. The second sipe 52b is generally inclined so as to extend toward the tire circumferential direction opposite to the first sipe 51b (downward in FIG. 2) as it goes inward in the tire axial direction.

The third sipe 52c formed only on the second shoulder land 52 extends from the inner end in the tire axial direction of the second inclined groove 52a until reaching the second intermediate main groove 63. This third sipe 52c is formed in such a manner that the second inclined groove 52a extends toward the second intermediate main groove 63.

The widths (dimensions in the tire axial direction) of the first central land 53 and the second central land 54 are the same. The widths of the first central land 53 and the second central land 54 are, for example, about 20% or more and 70% or less of the widths of the first shoulder land 51 and the second shoulder land 52.

A plurality of first notches 53a that are open to the central main groove 61 are formed at the widthwise edge of the first central land 53 on the central main groove 61 side. The first notch 53a is inclined with respect to the tire axial direction so as to face one tire circumferential direction side (lower side in FIG. 2) as it goes toward the center main groove 61 side. The plurality of first notches 53a are arranged at a real pitch in the tire circumferential direction. On the other hand, a plurality of second notches 53b that are open to the first intermediate main groove 62 are formed at the widthwise edge of the first central land 53 on the first intermediate main groove 62 side. The second notch 53b has the same shape as the first notch 53a, and faces toward the opposite side (upper side in FIG. 2) from the first notch 53a as it goes toward the first intermediate main groove 62 side. It's slanted like that. The plurality of second notches 53b are arranged in the tire circumferential direction at the same pitch as the first notches 53a. Each of the plurality of second notches 53b is arranged at an intermediate position between the first notches 53a in the tire circumferential direction.

A plurality of third notches 54 a that are open to the second intermediate main groove 63 are formed at the widthwise edge of the second central land 54 on the second intermediate main groove 63 side. The third notch 54a is inclined toward the second intermediate main groove 63 so as to face in the same direction as the first notch 53a. The plurality of third notches 54a are arranged in the tire circumferential direction at the same pitch as the first notches 53a.

The three main grooves 60, that is, the central main groove 61, the first intermediate main groove 62, and the second intermediate main groove 63, are all grooves mainly for ensuring drainage performance. The widths of these three main grooves 60 are approximately the same, but all three may have different widths, or two may be the same and one may be different. The width of the main groove 60 is, for example, about 20% or more and 60% or less of the width of each central land 53, 54, but is not limited thereto.

Returning to FIG. 1, the carcass ply 70 will be explained. The carcass ply 70 constitutes a ply that serves as the frame of the tire 1. The belt 31 of the tread 30 described above is arranged on the tire outer surface side of the carcass ply 70. In the tread 30, an inner liner 80, a carcass ply 70, a belt 31, and a cap ply 35 are laminated in this order from the tire inner cavity side to the tire outer surface side, and the tread rubber 36 is stacked on the tire outer surface side of the cap ply 35. is located.

The carcass ply 70 includes a ply main body portion 70A, a pair of left and right ply folded portions 70B, and a pair of left and right ply bent portions 70C. The ply body portion 70A is a portion that extends from the inner side of one bead core 11 in the tire axial direction, through one sidewall 20, the tread 30, and the other sidewall 20, to the inner side of the other bead core 11 in the tire axial direction. .

The ply folded portion 70B is folded back around the bead core 11 from the inner end of the ply body portion 70A in the tire radial direction, thereby extending outward in the tire radial direction on the outer side of the bead core 11 and the bead filler 12 in the tire radial direction. , and extends to the axially outer end of the tread 30 via the shoulder 40.

A portion of the ply folded-back portion 70B that is further outward in the tire radial direction than the outer end 12a of the bead filler 12 in the tire radial direction overlaps with the outer side in the tire axial direction of the ply main body portion 70A. The folded end 71a, which is the terminal end of the ply folded part 70B, extends to the tire lumen side at the tire axially outer end 32b of the inner belt 32, and overlaps the tire axially outer end 32b. The folded end 71b, which is the tip of the folded end 71a, is located slightly inward in the tire axial direction from the outer end 33a of the outer belt 33 in the tire axial direction. The folded ends 71b of the pair of left and right ply folded parts 70B face each other in the tire axial direction.

The ply bent portion 70C is a portion that is bent in a U-shape from the ply main body portion 70A around the bead core 11 and connected to the ply folded portion 70B. The ply bent portion 70C is in contact with the inner side of the bead core 11 in the tire axial direction. The ply main body portion 70A and the ply folded portion 70B are continuous via the ply bent portion 70C.

The carcass ply 70 has a configuration in which a plurality of parallel ply cords are coated with rubber. The ply cord is made of an insulating organic fiber cord such as polyester or polyamide, and functions as the frame of the tire 1. The carcass ply 70 having such a structure has a more characteristic configuration in the present disclosure, which will be described in detail later.

In addition, although the carcass ply 70 of the embodiment has a one-layer structure, the carcass ply 70 may have a structure of two or more layers. However, a one-layer structure is preferable because weight reduction can be achieved.

The chafer 13 of the bead 10 described above surrounds the inner end in the tire radial direction of the carcass ply 70 including the ply bent portion 70C. Further, the rim strip rubber 14 is disposed on the ply folded portion 70B of the carcass ply 70 and on the outer side of the Chehar 13 in the tire axial direction.

The inner liner 80 covers the inner surface of the tire between the pair of beads 10. Inner liner 80 covers the inner surface of carcass ply 70 in a region spanning tread 30, shoulder 40, and sidewall 20. Furthermore, the inner liner 80 covers the inner surface of the carcass ply 70 and the chafer 13 in a region extending from the sidewall 20 to the bead 10. Therefore, the inner liner 80 constitutes the inner wall surface of the tire 1. The inner liner 80 is made of air-permeable rubber and prevents air inside the tire from leaking to the outside.

Here, as the rubber employed for the bead filler 12, a rubber whose hardness is higher than at least the sidewall rubber 21 and the inner liner 80 is used. The hardness of the rubber is a value measured with a type A durometer (durometer hardness) in an atmosphere of 23° C. in accordance with JIS K6253.

For example, when the hardness of the sidewall rubber 21 is used as a reference, the hardness of the bead filler 12 is preferably about 1.2 times or more and 2.3 times or less the hardness of the sidewall rubber 21. The hardness of the rim strip rubber 14 is more preferably about 1 to 1.6 times the hardness of the sidewall rubber 21. With such hardness, a balance between flexibility as a tire and rigidity near the bead 10 can be ensured.

The above is the basic configuration of the tire 1 according to the embodiment. Next, the characteristic configurations of the carcass ply 70 and the belt 31 will be explained.

FIG. 3 is an exploded view schematically showing a part of the circumferential direction of the tire 1 when the tread rubber 36 and cap ply 35 that constitute the outer surface of the tread 30 are omitted from the direction of arrow III in FIG. 1. It is a diagram. That is, in FIG. 3, the belt 31 and carcass ply 70 in the tread 30 are shown. As described above, the belt 31 includes the inner belt 32 and the outer belt 33, but the outer belt 33 is illustrated as the belt 31 here. The belt 31 is arranged at the center of the tire in the axial direction. The outer end of the belt 31 in the tire axial direction covers a part of the folded end 71a of the ply folded part 70B of the carcass ply 70. In addition, when the belt 31 has a two-layer structure, if the outer end in the tire axial direction of at least one layer of the belt covers a part of the folded end 71a of the ply folded part 70B of the carcass ply 70. good. In FIG. 3, the belt 31 is cut in the circumferential direction in order to clarify the layer structure of the belt 31 and the carcass ply 70. Note that FIG. 3 shows the tire axial direction X and the tire circumferential direction C.

In addition, FIG. 3 also shows, in correspondence with FIG. One second inclined groove 52a is shown.

The carcass ply 70 includes a plurality of ply cords 70d arranged in parallel. The ply cord 70d is made of an insulating organic fiber cord such as polyester or polyamide. A plurality of ply cords 70d are covered with rubber to form a carcass ply 70. In the first shoulder land 51 and the second shoulder land 52 on the outside in the tire axial direction of the tread 30, the ply cord 70d of the folded end 71a of the carcass ply 70 is opposite to the inclination direction of the ply cord 70d of the ply main body 70A. tilted in the direction.

The belt 31 includes a plurality of belt cords 31d arranged in parallel. The belt cord 31d is made of steel cord or the like. The belt 31 is constructed by covering a plurality of belt cords 31d with rubber.

The plurality of ply cords 70d in the ply main body 70A arranged on the tread 30 are inclined at an angle θ1 with respect to the tire circumferential direction. This angle θ1 is an acute angle between the ply cord 70d and the tire circumferential direction. For example, the angle θ1 is preferably 55° or more and 75° or less, but is not limited to this range.

The direction in which the ply cord 70d of the ply main body portion 70A extends is the direction in which the first inclined groove 51a of the first shoulder land 51 and the second inclined groove 52a of the second shoulder land 52 extend in the ground contact width region 39. (the direction shown by straight line G in FIGS. 2 and 3).

FIG. 4A shows the arrangement relationship between the ply cord 70d of the ply main body 70A of the carcass ply 70 and the first inclined groove 51a. FIG. 4B shows the arrangement relationship between the ply cord 70d of the ply main body 70A of the carcass ply 70 and the second inclined groove 52a. As shown in FIG. 4A, the angle θ3 between the direction G in which the first inclined groove 51a extends in the ground contact width region 39 and the line C1 along the tire circumferential direction, and the ply cord 70d of the ply main body 70A of the carcass ply 70. The angle θ1 formed by the line C1 along the tire circumferential direction is approximately the same angle. Similarly, as shown in FIG. 4B, the angle θ3 between the direction G in which the second inclined groove 52a extends in the ground contact width region 39 and the line C1 along the tire circumferential direction and the ply main body 70A of the carcass ply 70 The angle θ1 between the ply cord 70d and the line C1 along the tire circumferential direction is approximately the same angle. Here, the angle θ1 is formed on one side in the tire axial direction (the left side in FIGS. 4A and 4B) with respect to the line C1 extending along the tire circumferential direction, and the angle θ3 is formed on the line C1 extending along the tire circumferential direction. On the other hand, it is formed on the other side in the tire axial direction (on the right side in FIGS. 4A and 4B). That is, the inclination direction of the ply cord 70d of the ply body portion 70A of the carcass ply 70 with respect to the tire circumferential direction is opposite to the inclination direction of the first inclined groove 51a and the second inclined groove 52a with respect to the tire circumferential direction in the ground contact width region 39. It is the direction. Note that it is preferable that the angle θ3 formed by the first inclined groove 51a and the second inclined groove 52a with the tire circumferential direction and the angle θ1 formed between the ply cord 70d and the tire circumferential direction are the same angle, They may be different from each other, and for example, it is preferable that the difference is within ±10°.

As shown in FIG. 3, the belt cord 31d of the embodiment extends in the same direction of inclination as the ply cord 70d disposed on the tread 30 with respect to the tire circumferential direction. Here, the same inclination direction side refers to a state in which the tire extends toward one side in the tire circumferential direction while being inclined to one side in the tire axial direction, and does not extend to the other side in the tire axial direction. means. The acute angle θ2 between the belt cord 31d and the tire circumferential direction is smaller than the acute angle θ1 between the ply cord 70d and the tire circumferential direction. Here, the sum of angle θ1 and angle θ2 is preferably 90°±5°.

In the embodiment, it is preferable that the angle θ4 between the ply cord 70d at the folded end 71a of the carcass ply 70 and the belt cord 31d is approximately 90°. That is, it is preferable that the direction in which the ply cord 70d at the folded end 71a of the carcass ply 70 extends and the direction in which the belt cord 31d extends are substantially orthogonal. For example, the angle θ4 is preferably 90°±10°.

Further, in the carcass ply 70 of the embodiment, each of the folded ends 71b of the left and right pair of folded ends 71a is located inside the ground contact ends at both ends of the ground contact width region 39, and is close to the ground contact ends. .

Specifically, in FIG. 3, the left folded end 71b is disposed within a predetermined tire axial direction region 39W1 that is set axially inward of the left side first ground contact end 39A. This tire axial direction region 39W1 has a width of 15% of the tire axial direction length L1 in the region from the first ground contact end 39A to the tire axial direction outer edge 62a of the first intermediate main groove 62. FIG. 2 also shows that the folded end 71b is arranged within the tire axial direction region 39W1.

On the other hand, the same applies to the right folded end 71b in FIG. 3, and the folded end 71b is arranged within a predetermined tire axial direction region 39W2 that is set inward in the tire axial direction from the right second ground contact end 39B. ing. This tire axial direction region 39W2 has a width of 15% of the tire axial direction length L2 in the region from the second ground contact end 39B to the tire axial direction outer edge 63a of the second intermediate main groove 63. FIG. 2 also shows that the folded end 71b is arranged within the tire axial direction region 39W2.

According to the tire 1 according to the embodiment described above, the following effects are achieved.

(1) The tire 1 according to the embodiment is arranged between a pair of beads 10 having a bead core 11, a pair of sidewalls 20 extending outward in the tire radial direction from each of the pair of beads 10, and a pair of sidewalls 20. The tread 30 has a tread surface 37 including a predetermined ground contact width region 39 and has a belt 31 embedded therein having a plurality of belt cords 31d, and a tread 30 which is disposed between a pair of beads 10 and has a plurality of ply cords 70d. A pneumatic tire comprising a carcass ply 70 having a tread 30, a plurality of lands 50 arranged along the circumferential direction of the tire, and a plurality of lands 50 arranged in the axial direction of the tire, A plurality of main grooves 60 extending in the circumferential direction of the tire, and the plurality of lands 50 include a first shoulder land 51 and a second shoulder land, which are a pair of left and right shoulder lands respectively arranged at both ends in the tire axial direction. 52, and a first center land 53 and a second center land 54 as center lands arranged between the first shoulder land 51 and the second shoulder land 52 in the tire axial direction, Each of the shoulder land 51 and the second shoulder land 52 extends in a direction intersecting the tire circumferential direction, is arranged at intervals in the tire circumferential direction, and at least a portion thereof extends in the ground contact width region 39. The carcass ply 70 has a plurality of first inclined grooves 51a and a plurality of second inclined grooves 52a arranged, and the carcass ply 70 has a ply main body 70A arranged between a pair of beads 10 and a pair of first inclined grooves 51a and a plurality of second inclined grooves 52a arranged between It has a pair of ply folded parts 70B which are each folded back at the bead core 11 of the bead 10, and whose folded ends 71a extend to the first shoulder land 51 and the second shoulder land 52 and overlap with the belt 31 in the tire radial direction. However, the inclination direction of the ply cord 70d in the ply main body 70A disposed on the tread 30 with respect to the tire circumferential direction is the inclination direction of the first inclined groove 51a and the second inclined groove 52a in the ground contact width region 39 with respect to the tire circumferential direction. and in the opposite direction.

The tire 1 of the embodiment has a plurality of first inclined grooves 51a of the first shoulder land 51 and a plurality of second inclined grooves of the second shoulder land 52, which extend in the same direction with respect to the tire circumferential direction. 52a, there is a possibility that PRCF, which is one of the components of the vehicle deflection described above, will occur. This PRCF occurs particularly depending on the direction in which the first inclined groove 51a and the second inclined groove 52a extend in the ground contact width region 39. Here, the ply cord 70d in the ply main body 70A disposed on the tread 30 of the tire 1 of the embodiment is the inclination of the first inclined groove 51a and the second inclined groove 52a in the tire circumferential direction in the ground contact width region 39. It extends at an angle in the opposite direction. Further, the ply cord 70d overlaps each of the first inclined groove 51a and the second inclined groove 52a in the tire thickness direction, that is, in the tire radial direction.

In the tire 1 of the embodiment, the ply cord 70d disposed on the tread 30 generates a torsional force according to the direction of inclination with respect to the tire circumferential direction during running. In the embodiment, this torsional force acts to cancel out the PRCF generated by the first inclined groove 51a and the second inclined groove 52a. This canceling effect is caused by the part of the ply cord 70d overlapping the first inclined groove 51a and the second inclined groove 52a being inclined in the opposite direction to the first inclined groove 51a and the second inclined groove 52a. This is caused by the fact that it extends. PRCF can be effectively canceled by adjusting the arrangement of the carcass ply 70 so that the direction of inclination of the ply cord 70d is opposite to the direction of inclination of the first inclined groove 51a and the second inclined groove 52a. can. That is, in the tire 1 of the embodiment, the PRCF can be adjusted by adjusting the arrangement of the carcass ply 70 and adjusting the inclination direction of the ply cord 70d. Therefore, according to the tire 1 of the embodiment, it is possible to increase the degree of freedom in the adjustment range of PRCF, and it is also possible to effectively suppress PRCF.

Further, in the first shoulder land 51 and the second shoulder land 52 on the outside in the tire axial direction of the tread 30, the ply cord 70d of the folded end 71a of the carcass ply 70 is arranged in the direction of inclination of the ply cord 70d of the ply main body 70A. is tilted in the opposite direction. Therefore, a decrease in tire balance that may occur due to the ply cord 70d of the ply main body portion 70A can be canceled out by the ply cord 70d of the folded end portion 71a.

(2) In the tire 1 according to the embodiment, the belt cord 31d of the belt 31 extends in the same inclination direction as the ply cord 70d disposed on the tread 30 with respect to the tire circumferential direction, and the belt cord The angle θ2 between the ply cord 31d and the tire circumferential direction is preferably smaller than the angle θ1 between the ply cord 70d disposed on the tread 30 and the tire circumferential direction.

In the tire 1 of the embodiment, PRCF is also generated by the belt cord 31d of the belt 31, and the PRCF depends on the inclination angle of the belt cord 31d. As in the embodiment, the angle θ2 between the belt cord 31d and the tire circumferential direction is preferably smaller than the angle θ1 between the ply cord 70d disposed on the tread 30 and the tire circumferential direction. Since the angle θ2 between the belt cord 31d and the tire circumferential direction is smaller than the angle θ1 between the ply cord 70d disposed on the tread 30 and the tire circumferential direction, the PRCF generated by the belt cord 31d and the The PRCFs generated by the first ply cord 71d are combined, and the effect of suppressing the PRCFs generated by the pattern components can be obtained.

(3) In the tire 1 according to the embodiment, it is preferable that the direction in which the ply cord 70d at the folded end 71a of the carcass ply 70 extends and the direction in which the belt cord 31d extends are substantially orthogonal.

As a result, the deformation in the torsional direction that occurs in the belt 31 when a slip angle is applied is efficiently returned to its original state when the SAT returns to the straight running state, and as a result, residual stress in the belt 31 is suppressed. be able to.

(4) In the tire 1 according to the embodiment, the angle θ3 between the first inclined groove 51a and the second inclined groove 52a and the tire circumferential direction and the tire circumference of the ply cord 70d arranged in the tread 30 are It is preferable that the difference between the angle θ1 and the direction is within ±10°.

Thereby, it is possible to increase the degree of freedom in the adjustment range of PRCF, and it is also possible to effectively suppress PRCF.

(5) In the tire 1 according to the embodiment, the first shoulder land of the folded ends 71b, which are the tips of the folded ends 71a facing each other in the tire axial direction, of the pair of ply folded parts 70B in the carcass ply 70 The folded end 71b on the 51 side is located in the tire axial direction in a region from the axially outer edge 62a of the first intermediate main groove 62 located at the outermost side in the tire axial direction to the first ground contact end 39A of the ground contact width region 39. The folded end 71b on the second shoulder land 52 side is arranged within the tire axial direction region 39W1 of 15% from the first ground contact end 39A with respect to the length L1, and the second With respect to the tire axial length L2 in the area from the axially outer edge 63a of the intermediate main groove 63 to the second ground contact end 39B of the ground contact width region 39, 15% of the tire axial direction from the second ground contact end 39B. Preferably, it is located within the region 39W2.

As a result, while ensuring the effect of suppressing PRCF by the ply cord 70d of the ply body part 70A of the carcass ply 70, the deterioration of the tire balance that may be caused by the ply cord 70d of the ply body part 70A can be prevented by the folded end part 71a. This can be canceled by the ply cord 70d.

Although the specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and even if modifications and improvements are made within the scope of achieving the purpose of the present invention, they will not fall within the scope of the present invention. It will be done.

For example, the pattern of the main groove and the center land between the first shoulder land 51 and the second shoulder land 52 on both sides in the axial direction of the tire is not limited to the aspect of the above embodiment, but may be arranged at the center in the axial direction of the tire. It may also be a pattern in which a pair of left and right main grooves are arranged on both sides of one central land.

The configuration according to the embodiment can be applied not only to pneumatic tires for passenger cars but also to pneumatic tires for various vehicles such as light trucks, trucks, and buses.

1 Tire (pneumatic tire)
10 bead 11 bead core 20 sidewall 30 tread 31 belt 31d belt cord 37 tread surface 39 ground contact width area 39A first ground contact end (ground contact end)
39B Second grounding end (grounding end)
39W1, 39W2 Tire axial area
50 Land 51 First shoulder land (Shoulder land)
51a First slanted groove (slanted groove)
52 Second shoulder land (shoulder land)
52a Second slanted groove (slanted groove)
53 First Central Land (Central Land)
54 Second Central Land (Central Land)
60 Main groove 62a, 63a Outer edge of main groove in tire axial direction 70 Carcass ply 70A Ply main body 70B Ply folded part 70d Ply cord 71a Folded end 71b Folded end

Claims (5)

a pair of beads having a bead core;
a pair of sidewalls extending outward in the tire radial direction from each of the pair of beads;
a tread that is disposed between the pair of sidewalls, has a tread surface including a predetermined ground contact width area, and has a belt embedded therein having a plurality of belt cords;
A pneumatic tire comprising: a carcass ply disposed between the pair of beads and having a plurality of ply cords,
The tread is
A plurality of lands arranged along the circumferential direction of the tire;
A plurality of main grooves arranged between the plurality of lands in the tire axial direction and extending in the tire circumferential direction,
The plurality of lands are
A pair of shoulder lands located at both ends of the tire in the axial direction,
at least one central land located between the pair of shoulder lands in the tire axial direction,
Each of the pair of shoulder lands extends in a direction intersecting the tire circumferential direction, is spaced apart from each other in the tire circumferential direction, and has a plurality of slopes, at least a part of which is arranged in the ground contact width region. has a groove,
The carcass ply has a ply main body disposed between the pair of beads, and is folded back from the ply main body at the bead core of the pair of beads, and the folded end extends to the shoulder land and is connected to the belt. a pair of ply folded portions that overlap in the tire radial direction;
A pneumatic tire, wherein an inclination direction of the ply cord with respect to the tire circumferential direction in the ply main body portion disposed on the tread is opposite to an inclination direction of the inclined groove with respect to the tire circumferential direction in the ground contact width region. The belt cord extends in the same inclination direction as the ply cord arranged on the tread with respect to the tire circumferential direction, and the angle θ2 between the belt cord and the tire circumferential direction is such that the belt cord is arranged on the tread. The pneumatic tire according to claim 1, wherein the angle θ1 between the ply cord and the tire circumferential direction is smaller than an angle θ1 between the ply cord and the tire circumferential direction. The pneumatic tire according to claim 1 or 2, wherein the extending direction of the ply cord at the folded end of the carcass ply and the extending direction of the belt cord are substantially perpendicular to each other. According to claim 1 or 2, the difference between the angle between the inclined groove and the tire circumferential direction and the angle between the ply cord arranged on the tread and the tire circumferential direction is within ±10°. pneumatic tires. Each of the folded ends, which are the tips of the folded ends of the pair of ply folded parts in the carcass ply, which are opposite to each other in the tire axial direction, is the axially outer end of the main groove located most outwardly in the tire axial direction. The pneumatic tire according to claim 3, wherein the pneumatic tire is disposed within a 15% axial region of the tire from the ground contact end with respect to the tire axial length in the region from the edge to the ground contact end of the ground contact width region.

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