JP2024042212A - pneumatic tires - Google Patents

Abstract

[Problem] To provide a pneumatic tire with improved steering stability. [Solution] A pneumatic tire with a tread 30 having a plurality of main grooves 60 extending in the tire circumferential direction, a plurality of lands 70 arranged between the main grooves 60 in the tire width direction, and a tread surface 37 including a predetermined ground contact width region 39, the land 70 including a central land 71 arranged in the center in the tire width direction, and a first intermediate land 72 and a second intermediate land 73 arranged on both sides of the central land 71, the intermediate lands 72, 73 having a plurality of first intermediate sipes 91A and second intermediate sipes 91B arranged at intervals in the tire circumferential direction and extending in a direction intersecting the tire circumferential direction, the total width of the intermediate lands 72, 73 being 30% or more of the width W of the ground contact width region 39, and the tire width direction lengths L3, L4 of the intermediate sipes 91A, 91B being 50% or less of the width of the intermediate lands 72, 73. [Selected Figure] Figure 2

Description

The present invention relates to pneumatic tires.

BACKGROUND ART Pneumatic tires have been known that include a tread in which a tread pattern is formed by a plurality of grooves. Examples of the plurality of grooves include a main groove along the circumferential direction of the tire, a narrow groove called a sipe formed on the land surface between the plurality of main grooves and extending in a direction intersecting the circumferential direction of the tire. Patent Document 1 discloses a tire in which steering stability is said to be improved by varying the width of the main grooves and forming sipes that cross the land on a specific land between the main grooves. .

JP2022-73064A

By the way, while increasing the width of the land between the main grooves improves the rigidity of the tread, it may lead to a decrease in ground contact. Sipe installed on land has the function of improving ground contact, but when it crosses land as in Patent Document 1, it is difficult to balance rigidity and ground contact, so it is difficult to improve steering stability. There is room for improvement.

Therefore, an object of the present invention is to provide a pneumatic tire with improved handling stability.

The pneumatic tire of the present invention has a plurality of main grooves extending in the tire circumferential direction, a plurality of lands arranged between the main grooves in the tire width direction, and a tread surface including a predetermined ground contact width area. A pneumatic tire with a tread, the land includes a center land located at the center in the width direction of the tire, and intermediate lands located on both sides of the center land, and the intermediate land extends around the circumference of the tire. a plurality of intermediate sipes arranged at intervals in the tire circumferential direction and extending in a direction intersecting the tire circumferential direction; the total width of the intermediate lands is 30% or more of the width of the ground contact width region; The length of the sipe in the tire width direction is 50% or less of the width of the intermediate land.

According to the present invention, a pneumatic tire with improved steering stability can be provided.

FIG. 2 is a diagram showing a half cross section of the tire according to the embodiment in the tire width direction. FIG. 1 is a partially enlarged front view showing a tread surface of a tire according to an embodiment.

Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is a diagram showing the internal structure of a tire 1, which is a pneumatic tire according to an embodiment, and shows a half cross section in the width direction of the tire. FIG. 2 is a partially enlarged front view of the tire 1, showing the tread surface 37 of the tire 1. FIG. The tire 1 according to the embodiment is, for example, a pneumatic tire for a passenger car.

First, the internal structure of the tire 1 will be explained with reference to FIG. The basic internal structure of the tire 1 is symmetrical in cross section in the tire width 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.

The cross-sectional view in FIG. 1 is a cross-sectional view in the width direction of the tire in an unloaded state in which the tire 1 is mounted on a specified rim (not shown) and filled with a specified internal pressure. Note that the standard rim refers to a standard rim defined by JATMA corresponding to the tire size. Further, the specified internal pressure is, for example, 180 kPa when the tire is for a passenger car.

In FIG. 1, the tire width direction is indicated by an arrow X, and the tire radial direction is indicated by an arrow Y. The tire width direction is a direction parallel to the tire rotation axis, and is a left-right direction in the plane of the paper in FIG. The inner side in the tire width direction is a direction approaching the tire equatorial plane S1 in the tire width direction, and is the left side in the drawing in FIG. The outer side in the tire width direction is the direction away from the tire equatorial plane S1 in the tire width direction, and is the right side in FIG. 1.

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 provided on both sides in the tire width direction, 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 tire includes a tread 30 disposed between a pair of beads 10, a carcass ply 40 disposed across the pair of beads 10, and an inner liner 50 disposed on the tire inner cavity side of the carcass ply 40. .

The bead 10 has a bead core 11, a bead filler 12 extending radially outward from the bead core 11, a rim strip rubber 13, and a rim protector 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 rim strip rubber 13 further surrounds the outside of the carcass ply 40, which is provided surrounding the bead core 11 and the bead filler 12. The rim strip rubber 13 contacts the inner part of the rim on which the tire 1 is mounted. A peak 13a is formed along the tire circumferential direction on the outer surface of the rim strip rubber 13 on the outer side in the tire width direction. The outer part of the rim strip rubber 13 in the tire width direction, including the peak 13a, constitutes a rim protector 14 that protects the rim from external damage. The rim protector 14 is continuous in an annular shape in the tire circumferential direction.

The sidewall 20 includes sidewall rubber 21 disposed on the outside of the carcass ply 40 in the tire width direction. The sidewall rubber 21 constitutes the outer wall surface of the tire 1. The sidewall rubber 21 is the part that flexes 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 40 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.

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 50 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 width direction is located further outward in the tire width direction than the outer end 33a of the outer belt 33 in the tire width 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 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 width direction is located further outward in the tire width direction than the outer end 32a of the inner belt 32 in the tire width 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 outer end 36b of the tread rubber 36 in the tire width direction extends beyond the outer end 35a of the cap ply 35 in the tire width direction and curves inward in the tire radial direction. An outer end 36b of the cap ply 35 in the tire width direction is covered with an outer end 21b of the sidewall rubber 21 in the tire radial direction.

A tread pattern 38 is provided on the tread surface 37. The tread pattern 38 has a characteristic configuration in the present disclosure, which will be described in detail later.

The carcass ply 40 is spanned between a pair of beads 10. The carcass ply 40 constitutes a ply that serves as the frame of the tire 1. The carcass ply 40 is embedded in the tire 1 in such a manner that it passes between the pair of beads 10 on the tire inner cavity side of the pair of sidewalls 20 and the tread 30. In the tread 30, a belt 31 is arranged on the outside of the carcass ply 40 in the tire radial direction.

The carcass ply 40 includes a plurality of ply cords (not shown). The plurality of ply cords extend, for example, in a plane along the width direction of the tire, and are arranged side by side in the tire circumferential direction. This ply cord is made of an insulating organic fiber cord such as polyester or polyamide. A carcass ply 40 is constructed by covering a plurality of ply cords with rubber.

The carcass ply 40 has a ply main body portion 40A, a ply folded portion 40B, and a bent portion 40C. The ply main body portion 40A is a portion that extends from the inner side of one bead core 11 in the tire width 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 width direction. . The ply folded portion 40B is a portion that extends outward in the tire width direction of the bead filler 12 on the outside in the tire width direction by being folded back around the bead core 11 from the inner end in the tire radial direction of the ply main body portion 40A. The bent portion 40C is a portion that is bent in a U-shape from the ply main body portion 40A around the bead core 11 and connected to the ply folded portion 40B. The ply main body portion 40A and the ply folded portion 40B are continuous via the bent portion 40C.

The carcass ply 40 of the embodiment has a two-layer structure in which a first carcass ply 41 and a second carcass ply 42 are stacked. In the ply main body portion 40A, the first carcass ply 41 is arranged on the tire inner cavity side of the second carcass ply 42. In the ply folded portion 40B, the first carcass ply 41 is arranged on the outside of the second carcass ply 42 in the tire width direction. The first carcass ply 41 of the ply folded portion 40B extends from the bent portion 40C to the middle of the bead filler 12. The second carcass ply 42 of the ply folded portion 40B extends from the bent portion 40C to near the center of the sidewall 20 in the tire radial direction. The tire radial outer end portion of the second carcass ply 42 of the ply folded portion 40B is overlapped with the second carcass ply 42 of the ply main body portion 40A.

A side reinforcing layer 45, which is a reinforcing layer made of a steel member, is arranged outside the bead filler 12 in the tire width direction. This side reinforcing layer 45 is sandwiched between the bead filler 12 and the ply folded portion 40B of the carcass ply 40, and further has a portion extending outward from the bead filler 12 in the tire radial direction.

Although the carcass ply 40 of the embodiment has a two-layer structure, the carcass ply 40 may have one layer or three or more layers. It is preferable that the carcass ply 40 is composed of a ply having a two-layer or more layered structure, since local deformation of the tire 1 near the mounting portion of the rim is sufficiently suppressed.

The inner liner 50 covers the inner surface of the tire between a pair of beads 10. The inner liner 50 covers the inner surface of the ply body 40A in the region from the tread 30 to the sidewall 20. The inner liner 50 also covers the inner surfaces of the ply body 40A and the rim strip rubber 13 in the region from the sidewall 20 to the bead 10. The inner liner 50 is made of air-resistant rubber and prevents air in the tire cavity 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 50 is used. The hardness of the rubber is JIS K6253-3:2012 durometer hardness type A.

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 13 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. Further, the hardness of the tread rubber 36 is preferably relatively low from the viewpoint of good ground contact and low fuel consumption, and for example, the durometer hardness type A is preferably about 50 or more and 60 or less.

The above is the internal structure of the tire 1 according to the embodiment. Next, with reference to FIG. 2, the tread pattern 38 of the tread 30 according to the embodiment will be described in detail. Note that FIG. 2 shows a tire width direction X and a tire circumferential direction C.

The tread pattern 38 of the embodiment includes a plurality of main grooves 60 and a plurality of lands 70 arranged between the main grooves 60 in the tire width direction. The plurality of main grooves 60 and the plurality of lands 70 both extend annularly along the tire circumferential direction. The tread pattern 38 of the embodiment is a so-called symmetrical pattern, and is a non-directional pattern in which the direction of rotation of the tire 1 is not specified.

The tread surface 37 of the tread 30 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 in the tire width 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 width direction does not normally contact the road surface.

Here, a portion of the tread rubber 36 on the outside in the tire width direction, from each of the first ground contact end 39A and the second ground contact end 39B to the tire radial direction outer end 21b of the sidewall rubber 21 (see FIG. 1). The part up to the vicinity is called shoulder 25. The shoulder 25 is a portion that transitions from the sidewall 20 to the ground contact width region 39. Note that FIG. 2 shows a region having a half width W1, which is half the width W of the ground contact width region 39 from the tire equator S2 to the first ground contact end 39A and the second ground contact end 39B.

Note that the contact edge here refers to the edge of the tire width direction of the contact patch under conditions where 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. That's true. 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 plurality of main grooves 60 include a pair of central main grooves 60A disposed at the center in the tire width direction, and a pair of intermediate main grooves 60B disposed on the outer sides of the pair of central main grooves 60A in the tire width direction.

Regarding the widths (dimensions in the tire width direction) of the main grooves 60 in the embodiment, the two central main grooves 60A have the same width, and the two intermediate main grooves 60B have the same width. The width of the central main groove 60A and the width of the intermediate main groove 60B may be the same or different. For example, the width of the central main groove 60A may be greater than the width of the intermediate main groove 60B, or conversely, the width of the intermediate main groove 60B may be greater than the width of the central main groove 60A.

The multiple lands 70 include one central land 71 arranged between the pair of central main grooves 60A, a first intermediate land 72 and a second intermediate land 73 arranged between the central main groove 60A and the intermediate main groove 60B, and a first shoulder land 74 and a second shoulder land 75 arranged at both ends in the tire width direction. Each land in the embodiment is formed in a rib shape that is continuous in the tire circumferential direction. The first intermediate land 72 and the first shoulder land 74 are arranged to the left of the central land 71 in FIG. 2. The second intermediate land 73 and the second shoulder land 75 are arranged to the right of the central land 71 in FIG. 2.

The center land 71 is arranged at a position where the tire equator S2 passes through the center in the width direction. The central land 71 has a plurality of central sipes 81 that open to the tread surface 37 , that is, the outer surface of the central land 71 . The central sipe 81 is a thin groove having a shape extending in a direction intersecting the tire circumferential direction. The groove width of the central sipe 81 is 1 mm or less.

The multiple central sipes 81 include multiple first central sipes 81A and multiple second central sipes 81B. The first central sipe 81A is arranged at the edge of the central land 71 on the first shoulder land 74 side (left side in FIG. 2). The second central sipe 81B is arranged at the edge of the central land 71 on the second shoulder land 75 side (on the right side in FIG. 2).

A plurality of first central sipes 81A and a plurality of second central sipes 81B are alternately arranged at intervals in the tire circumferential direction. The pitch in the tire circumferential direction of the plurality of first central sipes 81A and the pitch in the tire circumferential direction of the plurality of second central sipes 81B may be equal pitches or may be unequal pitches. The first central sipe 81A and the second central sipe 81B have the same arcuate shape, and a pair of the first central sipe 81A and the second central sipe 81B that are adjacent to each other in the tire circumferential direction are They are arranged symmetrically.

In FIG. 2, the first central sipe 81A opens into the central main groove 60A adjacent to the left side of the central land 71, and extends downward from its opening end toward one side in the tire circumferential direction, then curves slightly upward toward the other side in the tire circumferential direction, terminating without reaching the tire equator S2. The first central sipe 81A is generally inclined so that it extends toward one side in the tire circumferential direction (downward in FIG. 2) as it approaches the tire equator S2.

In FIG. 2, the second central sipe 81B opens into the central main groove 60A adjacent to the right side of the central land 71, extends from the open end toward the upper side, which is the other side in the tire circumferential direction, and then It curves briefly toward the lower side, which is one side, and ends without reaching the tire equator S2. The second central sipe 81B is generally inclined so as to extend toward the other side in the tire circumferential direction (upper side in FIG. 2) toward the tire equator S2.

The first central sipe 81A and the second central sipe 81B have opposite shapes, but have the same shape. In the following description, when explaining matters common to the first central sipe 81A and the second central sipe 81B, the first central sipe 81A and the second central sipe 81B will be collectively referred to as the central sipe 81. There is.

In the central land 71, the central sipes 81 are arranged at both ends of the central land 71 in the tire width direction.

The tire width direction length L1 of the first central sipe 81A is preferably 50% or less of the width G1 of the central land 71, and more preferably 30% or more and 50% or less of the width G1 of the central land 71. Similarly, the length L2 of the second central sipe 81B in the tire width direction is preferably 50% or less of the width G1 of the central land 71, and is 30% or more and 50% or less of the width G1 of the central land 71. It is more preferable if there is. Therefore, each of the first central sipe 81A and the second central sipe 81B may just reach the tire equator S2, which is the center in the tire width direction, from the end of the central land 71 in the tire width direction, and in that case, the tire width The directional lengths L1 and L2 are the longest. In any case, the first central sipe 81A and the second central sipe 81B do not have any portion that overlaps with each other in the tire circumferential direction.

The width G2 of the first intermediate land 72 is preferably 30% or more of the half width W1, which is half the width of the ground contact width region 39, and is 30% or more and 45% or less of the half width W1 of the ground contact width region 39. More preferred. Similarly, the width G3 of the second intermediate land 73 is preferably 30% or more of the half width W1 of the ground contact width region 39, and is 30% or more and 45% or less of the half width W1 of the ground contact width region 39. More preferred. That is, the sum of the width G2 of the first intermediate land 72 and the width G3 of the second intermediate land 73 is preferably 30% or more of the width W of the ground contact width area 39, and the width of the ground contact width area 39 is More preferably, the content of W is 30% or more and 45% or less.

The width G2 of the first intermediate land 72 and the width G3 of the second intermediate land 73 may be the same as each other or different. Also, the width G2 of the first intermediate land 72 and the width G3 of the second intermediate land 73 may be the same as the width G1 of the central land 71 or different.

Both the first intermediate land 72 and the second intermediate land 73 have a plurality of intermediate sipes 91 that are open to the tread surface 37, that is, the outer surface thereof. The intermediate sipe 91 is a thin groove having a shape extending in a direction intersecting the tire circumferential direction. The groove width of the intermediate sipe 91 is 1 mm or less.

The plurality of intermediate sipes 91 include a plurality of first intermediate sipes 91A and a plurality of second intermediate sipes 91B. The first intermediate sipe 91A is arranged at the edge of each of the first intermediate land 72 and the second intermediate land 73 on the first shoulder land 74 side (left side in FIG. 2). The second intermediate sipe 91B is arranged at the edge of each of the first intermediate land 72 and the second intermediate land 73 on the second shoulder land 75 side (on the right side in FIG. 2).

A plurality of first intermediate sipes 91A and a plurality of second intermediate sipes 91B are alternately arranged at intervals in the tire circumferential direction. The tire circumferential pitch of the plurality of first intermediate sipes 91A and the tire circumferential pitch of the plurality of second intermediate sipes 91B may be an equal pitch or an unequal pitch. The first intermediate sipe 91A and the second intermediate sipe 91B have the same arcuate shape, and a pair of the first intermediate sipe 91A and the second intermediate sipe 91B that are adjacent to each other in the tire circumferential direction are They are arranged symmetrically.

The first intermediate sipe 91A of the first intermediate land 72 opens into the intermediate main groove 60B adjacent to the left side of the first intermediate land 72 in FIG. The first intermediate land 72 extends for a short distance to the right side while sloping upward, and then bends in a mountain shape to the bottom side, which is the opposite side in the circumferential direction of the tire, and extends to the right side while sloping. It is terminated without being reached. On the other hand, the second intermediate sipe 91B of the first intermediate land 72 opens into the central main groove 60A adjacent to the right side of the first intermediate land 72, and extends from the opening end to the lower side which is the other side in the tire circumferential direction. The first intermediate land 72 extends for a short distance to the left side while sloping, then bends in a mountain shape to the upper side, which is the opposite side in the tire circumferential direction, and extends to the left side while sloping, and ends without reaching the center in the width direction of the first intermediate land 72. are doing.

The first intermediate sipe 91A of the second intermediate land 73 opens into the central main groove 60A adjacent to the left side of the second intermediate land 73 in FIG. It extends for a short distance to the right side while inclining, and then bends in a mountain shape to the lower side, which is the opposite side in the tire circumferential direction, and extends to the right side while inclining, without reaching the widthwise center of the second intermediate land 73. It is terminated. On the other hand, the second intermediate sipe 91B of the second intermediate land 73 opens into the intermediate main groove 60B adjacent to the right side of the second intermediate land 73, and extends from the opening end to the lower side on one side in the tire circumferential direction. It extends for a short distance to the left side while sloping, then bends in a mountain shape to the upper side, which is the opposite side in the tire circumferential direction, and extends to the left side while sloping, and ends without reaching the center in the width direction of the second intermediate land 73. are doing.

The first intermediate sipe 91A and the second intermediate sipe 91B have an arcuate shape in which the directions of the arcs are opposite to each other, but have the same shape. In the following description, when explaining matters common to the first intermediate sipe 91A and the second intermediate sipe 91B, the first intermediate sipe 91A and the second intermediate sipe 91B will be collectively referred to as the intermediate sipe 91. There is.

In each of the first intermediate land 72 and the second intermediate land 73, the intermediate sipes 91 are arranged at both ends of the intermediate land 72, 73 in the tire width direction.

The length L3 of the first intermediate sipe 91A in the tire width direction is preferably 50% or less of the width G2 of the first intermediate land 72, and is 35% or more and 50% or less of the width G2 of the first intermediate land 72. It is more preferable if Similarly, the length L4 of the second intermediate sipe 91B in the tire width direction is preferably 50% or less of the width G3 of the second intermediate land 73, and 35% of the width G3 of the second intermediate land 73. % or more and 50% or less is more preferable. Therefore, each of the first intermediate sipe 91A and the second intermediate sipe 91B may just reach the tire width direction center from the tire width direction end of each intermediate land, and in that case, the tire width direction length L3, L4 is the longest. In any case, the first intermediate sipe 91A and the second intermediate sipe 91B do not have any portions that overlap with each other in the tire circumferential direction.

Among the central sipe 81 and the intermediate sipes 91, when viewed in the tire circumferential direction, one first central sipe 81A and two first intermediate sipes 91A are arranged at approximately the same position in the tire circumferential direction. has been done. Therefore, these three sipes, which are substantially aligned in the tire circumferential direction, one first central sipe 81A and two first intermediate sipes 91A, are substantially parallel to each other along the tire width direction. Further, one second central sipe 81B and two second intermediate sipes 91B are shifted in the tire circumferential direction with respect to the first central sipe 81A and first intermediate sipe 91A that are adjacent in the tire circumferential direction. They are arranged at approximately the same position in the circumferential direction of the tire. Therefore, these three sipes, which are substantially aligned in the tire circumferential direction, one second central sipe 81B and two second intermediate sipes 91B, are substantially parallel to each other along the tire width direction.

Furthermore, both the first central sipe 81A and the second central sipe 81B have an arc shape that is substantially convex toward the tire circumferential direction, but the directions of the arcs are alternately opposite when viewed in the tire width direction. The direction is changing. Furthermore, both the first intermediate sipe 91A and the second intermediate sipe 91B have an arc shape that is substantially convex toward the tire circumferential direction, but the directions of the arcs are alternately opposite when viewed in the tire width direction. The direction is changing.

The first shoulder land 74 has a plurality of first slits 110 as the tread pattern 38. The second shoulder land 75 has a plurality of second slits 120 as the tread pattern 38. These slits 110 and 120 are grooves each having a groove width exceeding 1 mm, and extend in a direction intersecting the tire circumferential direction. Each of the first shoulder land 74 and the second shoulder land 75 does not have a narrow sipe with a groove width of 1 mm or less, such as the central sipe 81 and the intermediate sipe 91, as the grooves constituting the tread pattern 38. Not yet.

The first slits 110 of the first shoulder land 74 are arranged at intervals in the tire circumferential direction. The first slits 110 are arranged at equal or unequal pitches in the tire circumferential direction, for example, in the range of 20 mm to 40 mm. The first slits 110 have an arc shape that is gently convex on one side in the tire circumferential direction (the lower side in FIG. 2). The inner end of the first slit 110 in the tire width direction does not reach the intermediate main groove 60B adjacent to the first shoulder land 74, but terminates there. On the other hand, the outer end of the first slit 110 in the tire width direction extends to the shoulder 25 on the first shoulder land 74 side and opens to the outer surface of the shoulder 25.

The plurality of second slits 120 of the second shoulder land 75 are arranged at intervals in the tire circumferential direction. The plurality of second slits 120 are arranged at equal or unequal pitches in the tire circumferential direction, for example, in a range of 20 mm or more and 40 mm or less. The second slit 120 has an arcuate shape that is gently convex toward the tire circumferential side (upper side in FIG. 2) opposite to the first slit 110. The inner end of the second slit 120 in the tire width direction does not reach the intermediate main groove 60B adjacent to the second shoulder land 75, but ends there. On the other hand, the outer end of the second slit 120 in the tire width direction extends to the shoulder 25 on the second shoulder land 75 side and is open to the outer surface of the shoulder 25.

The first slit 110 and the second slit 120 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 slit 110 is arranged slightly outside the center in the tire width direction so that the first ground contact end 39A passes through the first slit 110. The second slit 120 is arranged slightly outside the center in the tire width direction so that the second ground contact end 39B passes therethrough.

With respect to the first slit 110 and the second slit 120, each of the above-mentioned central sipe 81 and intermediate sipe 91 is generally arranged between a pair of first slits 110 adjacent to each other in the tire circumferential direction, and in the tire circumferential direction. Two slits are arranged between each pair of second slits 120 adjacent to each other. That is, in the central sipe 81, a first central sipe 81A and a second central sipe 81B adjacent to one side (lower side in FIG. 2) of the first central sipe 81A in the tire circumferential direction form one set. These one set of central sipes 81 are arranged between a pair of first slits 110 adjacent to each other in the tire circumferential direction and between a pair of second slits 120 adjacent to each other in the tire circumferential direction. Further, in the intermediate sipe 91, a first intermediate sipe 91A and a second intermediate sipe 91B adjacent to the first intermediate sipe 91A on one side in the tire circumferential direction (lower side in FIG. 2) form one set, These one set of intermediate sipes 91 are arranged between a pair of first slits 110 adjacent to each other in the tire circumferential direction and between a pair of second slits 120 adjacent to each other in the tire circumferential direction.

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

(1) The tire 1 according to the embodiment includes a plurality of main grooves 60 extending in the tire circumferential direction, a plurality of lands 70 arranged between the main grooves 60 in the tire width direction, and a predetermined ground contact width region 39. A pneumatic tire is provided with a tread 30 having a tread surface 37, in which the land 70 includes a central land 71 located at the center in the width direction of the tire, and first intermediate lands located on both sides of the central land 71. 72 and a second intermediate land 73, each intermediate land 72, 73 is arranged as a plurality of intermediate sipes 91 that are arranged at intervals in the tire circumferential direction and extend in a direction intersecting the tire circumferential direction. Each has an intermediate sipe 91A and a second intermediate sipe 91B, and the sum of the width G2 of the first intermediate land 72 and the width G3 of the second intermediate land 73 is 30% or more of the width W of the ground contact width region 39. The length L3 of the first intermediate sipe 91A in the tire width direction is 50% or less of the width G2 of the first intermediate land 72, and the length L4 of the second intermediate sipe 91B in the tire width direction is equal to or less than 50% of the width G2 of the first intermediate land 72. It is 50% or less of the width G3 of the intermediate land 73.

The total width of the intermediate lands 72, 73 is 30% or more of the width W of the ground contact width region 39, so that the ratio of the width of the entire intermediate land to the ground contact width region 39 in the embodiment is relatively large. This improves the rigidity of the intermediate land. On the other hand, the intermediate sipes 91 reduce the rigidity, but since the intermediate sipes 91 are relatively short, at 50% or less of the width of the intermediate land, a good balance between rigidity and ground contact is ensured. In other words, the length of the intermediate sipes 91 can be adjusted to adjust the ground contact in a suitable direction. The improvement in the rigidity and the improvement in the ground contact of the intermediate land combine to improve the steering stability of the tire 1. Note that the rigidity tends to decrease when the number of intermediate sipes 91 is large, but for example, when the hardness of the tread rubber 36 is low, at 50 or more and 60 or less, the decrease in rigidity can be suppressed by shortening the length of the intermediate sipes 91.

(2) In the tire 1 according to the embodiment, the sum of the width G2 of the first intermediate land 72 and the width G3 of the second intermediate land 73 is 30% or more and 45% or less of the width W of the ground contact width region 39. The length L3 of the first intermediate sipe 91A in the tire width direction is 35% or more and 50% or less of the width G2 of the first intermediate land 72, and the length L4 of the second intermediate sipe 91B in the tire width direction is preferably 35% or more and 50% or less of the width G3 of the second intermediate land 73.

As a result, the stiffness of the intermediate land and the ground contact are improved, and the steering stability of the tire 1 is improved.

(3) In the tire 1 according to the embodiment, the intermediate sipes 91 are arranged at both ends in the tire width direction of the first intermediate land 72 and the second intermediate land 73, respectively. .

By arranging the intermediate sipes 91 at both ends of the intermediate land in the tire width direction, the substantial hardness of the intermediate land is appropriately reduced. As described above, the handling stability of the tire 1 is improved by adding the point that the hardness of the intermediate land is appropriately reduced to the improvement in the rigidity of the intermediate land.

(4) In the tire 1 according to the embodiment, the tread 30 includes a tread rubber 36, and the hardness of the tread rubber 36 is JIS K6253-3:2012 durometer hardness Type A, which is 50 or more and 60 or less. is preferred. This provides good ground contact and low fuel consumption.

Since the first shoulder land 74 and the second shoulder land 75 have no sipes, their rigidity is improved and toe-heel wear caused by the sipes does not occur. Note that the first shoulder land 74 and the second shoulder land 75 are arranged between the first slits 110 adjacent in the tire circumferential direction and between the second slits 120 adjacent in the tire circumferential direction, respectively. Although the tire has blocks arranged in the circumferential direction, it is preferable that the number of blocks arranged in the tire circumferential direction is relatively small, about 64, from the viewpoint of improving rigidity. When the number of blocks between the first slits 110 and the second slits 120 in the tire circumferential direction is about 64, the first slits 110 and the second slits 120 also have the same number of 64. The number of central sipes 81 and intermediate sipes 91 in the embodiment is about twice the number of first slits 110 and second slits 120, respectively, and is about 128, for example.

That is, in the tire 1 according to the embodiment, the tread 30 has the first shoulder land 74 and the second shoulder land 75 on both sides in the tire width direction, and the first shoulder land 74 and the second shoulder land 75 have the first shoulder land 74 and the second shoulder land 75. A plurality of blocks are provided at intervals in the tire circumferential direction, and the number of intermediate sipes 91 arranged in the tire circumferential direction is preferably twice the number of blocks arranged in the tire circumferential direction. This improves the rigidity of the shoulder land.

It should be noted that the present invention is not limited to the above-described embodiments, and even if modifications, improvements, etc. are made within the scope of achieving the object of the present invention, they are still within the scope of the present invention.

The configuration of the embodiment described above can be employed as tires for various vehicles such as light trucks, trucks, and buses in addition to passenger cars.

Examples will be described below. The ratio of the total width of the intermediate land to the width of the contact width area is in the range of 25% or more and 50% or less, and the ratio of the length in the tire width direction of one intermediate sipe to the width of the intermediate land is 30% or more and 55% or less. Twelve types of tires, which were appropriately combined within the following range, were evaluated using a simulation model. Table 1 shows the data of these tires, divided into Examples 1 to 7 that meet the conditions of the present invention and Comparative Examples 1 to 5 that do not meet the conditions of the present invention. In addition, in Table 1, "the ratio of the total width of the intermediate land to the width of the contact width area" is expressed as "ratio of the intermediate land (%)", and "the length of the intermediate sipe in the tire width direction to the width of the intermediate land" ``Ratio of intermediate sipes'' is expressed as ``Ratio of intermediate sipes (%)''.

Note that the tires of Examples 1 to 7 and Comparative Examples 1 to 5 all have the same basic configuration as the above embodiment. Further, the data on the intermediate land ratio and the intermediate sipe length ratio of each tire shown in Table 1 are data obtained when the tire is mounted on a regular rim and under no load at a regular internal pressure.

The steering stability, ground contact, and CP (cornering power) of the tires of Examples 1 to 7 and Comparative Examples 1 to 5 were measured by simulation. In measuring steering stability and ground contact, an air pressure of 260 kPa was applied, and a load of 70% of the maximum load of the tire's load index was applied. Moreover, when measuring CP, the air pressure was set to 230 kPa, and a load of 70% of the maximum load at the load index of the tire was applied.

For CP evaluation, the tire of Example 1 was evaluated as an index of 100, and other tires were evaluated as an index, and the larger the index evaluation value, the better. The evaluation of ground contact is based on the footprint of the tire in contact with the ground under the above load. Specifically, when the ground contact area of the intermediate land of Example 1 is used as a reference, the evaluation is based on the ratio of the ground contact area of the intermediate land of each example and each comparative example to the reference area. As for the evaluation, when the ground contact area of only the intermediate land is taken as 100%, ◎ if it is 100% or more, ○ if it is 90% or more and 99% or less, △ or 80% if it is 80% or more and 89% or less. If it is less than that, it is marked as ×.

The evaluation of steering stability is performed based on CP and ground contact. If the CP is 100 or more and the ground contact is 0, the vehicle is given a rating of ◎, indicating that the steering stability is particularly good. If the CP is 100 or more, but the ground contact is △, the steering stability is considered to be good and a rating of ◯ is given. On the other hand, if the CP is 96 or more and 99 or less, the steering stability is insufficient regardless of the ground contact evaluation result, so a △ is given. Furthermore, when the CP is 95 or less, the steering stability deteriorates regardless of the ground contact evaluation result, and therefore, an x is given to the vehicle. In other words, regarding the evaluation of steering stability, ◎ indicates that the steering stability is particularly good, ○ indicates that the steering stability is good, △ indicates that the steering stability is insufficient, × indicates poor steering stability.

According to Table 1, it can be seen that when the ratio of the intermediate land is less than 30% as in Comparative Examples 1 to 3, the ground contact is good, but the CP is low and the steering stability is not ensured. In Comparative Examples 4 and 5, the ratio of intermediate land is 30% or more, but it can be seen that when the ratio of intermediate sipes exceeds 50%, the CP is low and the steering stability is not improved. On the other hand, in Examples 1 to 6 of the present invention, ground contact and CP were ensured in a well-balanced manner, and the steering stability was generally good. In Example 7, the ratio of intermediate land was as high as 50%, so although there was an element that improved steering stability by increasing the rigidity and CP, the rigidity was too high and the ground contact deteriorated, which caused difficulty in maneuvering. The rating was 0 because it affected stability. In the tire of the example, when the ratio of the intermediate land is large and the ratio of the intermediate sipes is small, the rigidity of the intermediate land increases and the CP increases. but. If the ratio of the intermediate land is large and the rigidity is too high, the road following performance will decrease, the linearity of the vehicle behavior will decrease, and the steering stability will be impaired. In order to obtain these characteristics in a well-balanced manner, the total width of the intermediate land is 30% or more of the width of the contact width area, and the length of the intermediate sipe in the tire width direction is 50% or less of the width of the intermediate land. This is effective. In addition, when a test was conducted applying the conditions of the present invention to a fuel-efficient tire having a low durometer hardness type A of 50 or more and 60 or less, it showed good handling stability.

1. Tires (pneumatic tires)
30 Tread 37 Tread surface 39 Contact width region 40 Carcass ply 60 Main groove 70 Land 71 Central land 72 First intermediate land (intermediate land)
73 Second Intermediate Land (Intermediate Land)
91 Intermediate sipe G2 Width of first intermediate land G3 Width of second intermediate land L3 Length of first intermediate sipe in tire width direction L4 Length of second intermediate sipe in tire width direction W Width of contact width region

Claims (5)

A plurality of main grooves extending in the circumferential direction of the tire;
a plurality of lands arranged between the main grooves in the tire width direction;
A pneumatic tire comprising a tread surface including a predetermined ground contact width area,
The land includes a central land located at the center in the width direction of the tire;
intermediate land located on both sides of the central land,
The intermediate land has a plurality of intermediate sipes arranged at intervals in the tire circumferential direction and extending in a direction intersecting the tire circumferential direction,
The total width of the intermediate land is 30% or more of the width of the ground contact width region,
A pneumatic tire, wherein the length of the intermediate sipe in the tire width direction is 50% or less of the width of the intermediate land. The total width of the intermediate land is 30% or more and 45% or less of the width of the ground contact width region,
The pneumatic tire according to claim 1, wherein the length of the intermediate sipe in the tire width direction is 35% or more and 50% or less of the width of the intermediate land. The pneumatic tire according to claim 1 or 2, wherein the intermediate sipes are arranged at both ends in the tire width direction of the intermediate land. The pneumatic tire according to claim 1 or 2, wherein the tread includes tread rubber, and the hardness of the tread rubber is JIS K6253-3:2012 durometer hardness type A of 50 or more and 60 or less. The tread has shoulder lands on both sides in the tire width direction,
The shoulder land is provided with a plurality of blocks at intervals in the tire circumferential direction,
The pneumatic tire according to claim 1 or 2, wherein the number of the intermediate sipes arranged in the tire circumferential direction is twice the number of the blocks arranged in the tire circumferential direction.

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