CN117984696A - Tire with a tire body - Google Patents

Abstract

The invention provides a tire capable of improving drainage performance and steering stability on wet road surface. The tire is provided with: a plurality of main grooves (10) extending in the tire circumferential direction on the tread surface; and a plurality of land sections (20) partitioned by the main trench (10). At least 1 land portion (20) (e.g., quarter land portion (23)) includes: a sipe (44); and shallow grooves (50) formed shallower than the sipes (44). The sipe (44) has: an opening end (44 a) which is opened in the main groove (10); and a closed end (44 b) closed within the land portion (20). The shallow groove (50) extends so as to surround the sipe (44) in a tread plan view, and is connected to the main groove (10) where the open end (44 a) is open.

Description

Tire with a tire body

Technical Field

The present invention relates to a tire having sipes formed in land portions of a tread portion.

Background

As described in patent documents 1 to 4, a tread structure including land portions in which sipes are formed is often used for an automobile tire. The water removal effect of sipes is known to contribute to improved drainage performance and steering stability on wet road surfaces. Although the sipe connected to the main groove can exert a water removal effect even when water is introduced from the main groove, a specific structure for further improving drainage performance and steering stability performance on a wet road surface is not known from the viewpoint of improvement.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2021-160578

Patent document 2: japanese patent laid-open No. 2020-168944

Patent document 3: japanese patent laid-open No. 2018-184345

Patent document 4: japanese patent laid-open publication 2016-159665

Disclosure of Invention

The purpose of the present invention is to provide a tire that can improve drainage performance and steering stability performance on wet road surfaces.

The tire of the present invention comprises: a plurality of main grooves extending in the tire circumferential direction on the tread surface; and a plurality of land portions partitioned by the main trench, at least 1 of the land portions including: a sipe; and a shallow groove formed shallower than the sipe, the sipe having: an open end at the main trench opening; and a closed end closed within the land portion, the shallow groove extending so as to surround the sipe in a tread plan view and being connected to the main groove of the open end opening.

Drawings

Fig. 1 is a tire meridian cross-sectional view schematically showing a tire according to the present embodiment.

Fig. 2 is an expanded view showing a tread pattern.

Fig. 3 is an enlarged view showing a main portion of the tread surface.

Fig. 4 is a perspective view showing a main portion of the tread surface.

FIG. 5 is a cross-sectional view of the sipe along a widthwise centerline.

Fig. 6 is an X-X cross-sectional view of fig. 3.

Fig. 7 is an enlarged view showing a main portion of the tread surface.

Fig. 8 is an expanded view showing a tread pattern.

Fig. 9 is an expanded view showing a modification of the tread pattern.

Description of the reference numerals

3F … tread surface, 10 … main groove, 11 … shoulder main groove, 12 … central main groove, 13 … shoulder main groove, 20 … land portion, 21 … shoulder land portion, 22 … quarter land portion, 23 … quarter land portion, 24 … shoulder land portion, 40 … sipe, 44 … sipe, 44a … open end, 44b … closed end, 50 … shallow groove, 51 … first groove portion, 52 … second groove portion, 53 … third groove portion, 54 … partition wall.

Detailed Description

An embodiment of the present invention will be described with reference to the accompanying drawings.

Tire

The tire T of the present embodiment shown in fig. 1 is a pneumatic radial tire for an automobile, and includes: a pair of bead portions 1; a sidewall portion 2 extending radially outward of the tire from the bead portion 1; and tread portions 3 connected to the respective tire radial direction outer ends of the side wall portions 2. An annular bead core 1a is embedded in the bead portion 1. The bead core 1a is formed by covering a binding body such as a wire with rubber. A bead filler 1b is disposed radially outward of the bead core 1a. The bead filler 1b is formed of rubber having a triangular cross section extending radially outward from the bead core 1a.

Here, the tire radial direction is a direction along the diameter of the tire T, and corresponds to the up-down direction in fig. 1. In fig. 1, the upper side is the tire radial direction outer side, and the lower side is the tire radial direction inner side. The tire axial direction is a direction parallel to the rotation axis of the tire T, and corresponds to the left-right direction in fig. 1. The side closer to the tire equator TC is the tire axial inner side, and the side farther from the tire equator TC is the tire axial outer side. The tire equator TC is: a virtual line located at the tire axial center of the tire T and orthogonal to the tire rotation axis in a tread plan view. The tire circumferential direction is a direction around the rotation axis of the tire T.

The tire T is provided with: a carcass 4 extending annularly and straddling between the pair of bead portions 1. The carcass 4 is turned up from the inner side toward the outer side in the tire axial direction so as to sandwich the bead core 1a and the bead filler 1 b. The carcass 4 is formed of carcass cord, and the carcass cord is covered with rubber to form the carcass cord. The carcass cords are aligned in a direction intersecting the tire circumferential direction (e.g., a direction at an angle of 75 to 90 degrees with respect to the tire circumferential direction). For the material of the carcass cord, metal such as steel, organic fiber such as polyester, rayon, nylon, aramid, etc. are preferably used.

The tire T has: and a belt layer 5 laminated on the outer side of the carcass 4 in the tire radial direction. The belt layer 5 is formed of a plurality of (2 in this embodiment) belt plies 5a, 5b stacked on each other. The belt cords 5a, 5b are each formed by covering a belt cord with rubber. The belt cords are aligned in a direction inclined with respect to the tire circumferential direction (for example, a direction at an angle of 20 to 30 degrees with respect to the tire circumferential direction). For the material of the belt cord, a metal such as steel is preferably used. The belt cords 5a, 5b are laminated in such a manner that the belt cords cross each other in opposite directions therebetween.

The tire T is provided with: and a belt reinforcing material 6 laminated on the outer side of the belt layer 5 in the tire radial direction. The belt reinforcing material 6 is formed of a belt reinforcing cord, and the belt reinforcing cord is covered with rubber to form the belt reinforcing cord. The belt reinforcing cords are aligned substantially parallel to the tire circumferential direction. The belt reinforcing cord is formed by winding 1 or more belt reinforcing cords covered with rubber, for example, in a spiral manner in the tire circumferential direction. As the material of the belt reinforcing cord, the above-mentioned organic fiber is preferably used. In the present embodiment, the belt reinforcing material 6 covers the entire surface of the belt layer 5, but may be configured to cover only both ends of the belt layer 5.

The tire T is provided with: an inner liner 7 provided on the inner surface of the tire T. The liner 7 is made of a rubber excellent in air shielding properties such as butyl rubber. The inner liner 7 has a function of maintaining the inner pressure of the tire T.

[ Tread Pattern ]

The tread pattern shown in fig. 2 is formed on the tread surface 3f, which is the outer circumferential surface of the tread portion 3. The tire T is provided with: a plurality of main grooves 10 extending in the tire circumferential direction (corresponding to the up-down direction in fig. 2) on the tread surface 3 f; and a plurality of land portions 20 partitioned by the main grooves 10. The main groove 10 is provided with a wear indicator portion, not shown. The main groove 10 has a maximum groove width of 4mm or more and a maximum groove depth of 5mm or more. The groove width is measured as the distance between the intersection points of the land portion 20 surface and the groove wall in the direction orthogonal to the extending direction (longitudinal direction). The same applies to the width of the sipe 40 and the width of the lateral groove 30 described later. The main groove 10 is a straight groove, but not limited thereto, and may be a zigzag groove.

The dimensions of the main groove 10, the lateral groove 30, the sipe 40, and the like described later are measured in a non-loaded state in which the tire T mounted on the regular rim is filled with the regular internal pressure. The normal rim is: in a specification system including a specification according to which a tire is mounted, a rim defined for each tire according to the specification is, for example, a standard rim in the JATMA specification, and a "measuring rim" in the TRA specification and the ETRTO specification. The normal internal pressure is: in a specification system including specifications according to which tires are based, air pressure defined for each tire is based on each specification, and in the case of a tire for a truck or a tire for a light truck, the highest air pressure is the highest air pressure in the JATMA specification, and the maximum value described in the table "tire load limit under various cold inflation pressures" is the TRA specification, and the inflation pressure is the ETRTO specification. In the case of a car tire, 180kPa is usually set, but in the case of a tire described as "Extra Load" or "reinfored", 220kPa is set.

In the present embodiment, 3 main grooves 10 are provided on the tread surface 3f, and 4 land portions 20 are partitioned by the 3 main grooves 10. The 3 main grooves 10 include: a pair of shoulder main grooves 11, 13 located on the outermost side in the tire axial direction among these main grooves; and a central main groove 12 located between the pair of shoulder main grooves 11, 13. The center main groove 12 is provided on the tire equator TC. The 4 land portions 20 include: a pair of shoulder land portions 21, 24 formed adjacent to the tire axial outer sides of the shoulder main grooves 11, 13; and a pair of quarter land portions 22, 23 formed adjacent to the tire axial inner sides of the shoulder main grooves 11, 13.

The shoulder land portions 21, 24 each include a ground contact end TE. The ground TE is: the tire T mounted on the regular rim is filled with a regular internal pressure and placed vertically on a flat road surface, and at the outermost position in the tire axial direction of the ground contact surface when a regular load is applied. The normal load is: the load specified for each tire according to each specification in the specification system including the specification according to which the tire is based is "maximum load capacity" in the JATMA specification, the maximum value described in the table "tire load limits under various cold inflation pressures" in the TRA specification, and "load capacity" in the ETRTO specification. In the case of a tire for a car, the load is 88% of the load. In the case of a tire for racing, the normal load is 392N.

The land portions 20 are formed with lateral grooves 30 (lateral grooves 31 to 33) and notched sipes 40 (sipes 41 to 45), respectively, which extend in a direction intersecting the tire circumferential direction. The cross grooves 30 have a groove width exceeding 1.5mm, preferably having a maximum groove width of 1.8mm or more. The cross groove 30 has a maximum groove depth of preferably 3.0mm or more, more preferably 4.4mm or more. The maximum groove depth of the lateral groove 30 is equal to or less than the maximum groove depth of the main groove 10. Sipe 40 has a maximum width of 1.5mm or less. The sipe 40 has a maximum depth of preferably 2.0mm or more, more preferably 3.0mm or more. The maximum depth of the sipe 40 is equal to or less than the maximum depth of the sipe 30.

In the present embodiment, a tread pattern that is asymmetric with respect to the tire equator TC is formed. The tire T is: an assembling direction specifying type tire with respect to an assembling direction of a vehicle is specified. The inner region IN is a region on the vehicle inner side (IN side) when mounted on the vehicle with reference to the tire equator TC, and the outer region OUT is a region on the vehicle outer side (OUT side) when mounted on the vehicle with reference to the tire equator TC. The shoulder land portion 21, the shoulder main groove 11, and the quarter land portion 22 are provided IN the inner region IN, respectively. The quarter land portion 23, the shoulder main groove 13, and the shoulder land portion 24 are provided in the outer region OUT, respectively.

An identifier for specifying the fitting direction with respect to the vehicle is provided on the outer surface of the tire T. The designation of the fitting direction is performed as follows: for example, the outer surface of the side wall portion 2 disposed on the vehicle inner side is provided with a logo (for example, "instride") on the vehicle inner side when mounted on the vehicle, and/or the outer surface of the side wall portion 2 disposed on the vehicle outer side is provided with a logo (for example, "OUTSIDE") on the vehicle outer side when mounted on the vehicle. The tire T is not limited to the fitting direction-designated tire, and therefore, a tread pattern symmetrical with respect to the tire equator TC may be formed.

[ Quarter land portion of outer zone ]

As shown in fig. 3 and 4, the quarter land portion 23 includes: a sipe 44; and shallow grooves 50 formed shallower than the sipe 44. The sipe 44 has: an open end 44a that opens in the main groove 10 (specifically, the shoulder main groove 13); and a closed end 44b closed within the land portion. That is, the sipe 44 has a semi-closed configuration opening in the shoulder main groove 13. The shallow groove 50 extends so as to surround the sipe 44 in a tread plan view, and is connected to the main groove 10 whose open end 44a is open. Such a sipe 44 is repeatedly formed in the tire circumferential direction, and a shallow groove 50 surrounding the sipe 44 is formed. The shallow trench 50 is connected only to the main trench 13 of the pair of main trenches 12, 13 that demarcate the quarter land portion 23, and is not connected to the main trench 12. The shallow grooves 50 are not yet connected to the sipe 40 and the sipe 30.

Although the sipe 44 can perform the water removal function by introducing water from the main groove 13, the provision of the shallow grooves 50 as described above can further introduce the water around the sipe 44 to improve the water removal function, and further can improve the drainage performance and the steering stability on a wet road surface. Further, the provision of the shallow grooves 50 enhances the soft performance around the edges of the sipe 44 and makes it easy to attach to the road surface (the ground contact performance is improved), so that the performance is excellent in terms of ensuring the steering stability on the wet road surface, and the improvement of the braking performance on the wet road surface can be facilitated. However, if the circumference of the edge of the sipe 44 is excessively moved, there is a possibility that the grounding property is deteriorated instead, and therefore, the shallow groove 50 is formed shallower than the sipe 44.

As shown in fig. 5, in the present embodiment, the depth of the sipe 44 varies in the extending direction. The sipe 44 has: a base portion extending at a relatively greater depth D44a from the open end 44a toward the closed end 44 b; a distal portion extending from the closed end 44b toward the open end 44a at a relatively small depth D44 b; and an intermediate portion having a depth that gradually changes to join the base portion and the end portion. In one example, depth D44a is 6.5mm and depth D44b is 3mm. In the present embodiment, the groove depth D50 (see fig. 6) of the shallow groove 50 is set smaller than the minimum depth D44b of the sipe 44, but may be set smaller than the maximum depth D44a of the sipe 44.

Fig. 6 is an X-X cross-sectional view of fig. 3. From the viewpoint of improving the water removal effect by the sipe 44, it is preferable that the sipe 44 has a width W44 of 1.0mm or more. Preferably, the sipe 44 is formed to have a larger width than the other sipe 40 not surrounded by the shallow groove 50, for example, the sipe 43 formed in the same quarter land portion 23. In one example, the sipe 43 has a width of 0.6mm, whereas the sipe 44 has a width W44 of 1.5mm. The sipe 44 is formed as a two-dimensional sipe whose shape does not change in the depth direction, but is not limited to this, and may be a three-dimensional sipe including a portion whose shape changes in the depth direction.

In the present embodiment, the shallow trench 50 extends with a constant trench depth D50. In order to secure the improvement effect by the shallow trench 50, the trench depth D50 is preferably 0.8mm or more. From the viewpoint of suppressing deterioration of grounding property, the trench depth D50 is preferably 1.5mm or less. The width W50 of the shallow trench 50 is, for example, 0.5 to 1.0mm. The groove width W50 is smaller than the width W44 of the sipe 44, but is not limited thereto. The contour of the groove edge 50E formed by the surface of the land portion 20 and the groove wall of the shallow groove 50 is formed by an arc, whereby edge pressure can be reduced. The radius of curvature R of the circular arc is, for example, 0.3mm or more. In one example, the groove depth D50 is 1.0mm, the groove width W50 is 0.8mm, and the radius of curvature R is 0.3mm.

In order to secure the improvement effect by the shallow grooves 50, the gap G1 between the sipe 44 and the shallow grooves 50 in the width direction of the sipe 44 is preferably 1.5mm or less, more preferably 1.0mm or less. From the viewpoint of suppressing deterioration of grounding property, the interval G1 is preferably 0.8mm or more. In one example, the interval G1 is 1.0mm. In the present embodiment, the interval G1 is substantially constant except for the acute angle portion formed by the sipe 44 and the shoulder main groove 13. At the acute angle portion, the shallow groove 50 is away from the sipe 44 so as not to interfere with a low stage 23s (or chamfer) described later. The distance G2 (see fig. 3) between the closed end 44b and the shallow groove 50 in the extending direction of the sipe 44, which is measured along the widthwise center line of the sipe 44, is, for example, 5.0 to 10.0mm.

As long as the sipe 44 and the shallow groove 50 surrounding the sipe 44 as described above are included in at least 1 land portion 20. As described above, an example in which they are included in the quarter land portion 23 is shown in the present embodiment. Since the quarter land portion 23 includes the sipe 44 and the shallow groove 50 which open outward in the tire axial direction, the drainage performance of the shoulder main groove 13 can be improved. However, the sipe 44 and the shallow groove 50 may be connected to the central main groove 12. The shoulder land portions 21 and 24 or the center land portion 25 described later may include sipes 44 and shallow grooves 50.

In the present embodiment, the land portions 20 (i.e., the quarter land portions 23) including the sipes 44 and the shallow grooves 50 are provided as ribs that extend continuously in the tire circumferential direction. In the present embodiment, the quarter land portion 23 does not include the transverse grooves 30. The quarter land portion 23 is ribbed, so that, although including the sipe 44 and the shallow groove 50, the decrease in rigidity of the land portion is suppressed, and therefore, it is convenient to ensure the steering stability performance. However, the land portion including the sipe 44 and the shallow groove 50 is not limited to this, and may be a block row in which a plurality of blocks are arranged in the tire circumferential direction.

In the present embodiment, the sipe 44 and the shallow groove 50 are provided in the outer region OUT. The sipe 44 and the shallow groove 50 are used to improve the drainage performance, and the land rigidity of the outer region OUT is suppressed from being lowered, so that the steering stability performance is easily ensured. Further, since the sipe 44 and the shallow groove 50 are opened in the main groove 10, the contact length along the tire circumferential direction is increased and the contact pressure is reduced, so that the contact performance of the outer region OUT is easily ensured. However, the sipe 44 and the shallow groove 50 may be provided IN the inner region IN.

As shown in fig. 3 and 4, the shallow trench 50 includes: a first groove 51 that is isolated from the sipe 44 on one side in the tire circumferential direction; a second groove portion 52 that is isolated from the sipe 44 on the other side in the tire circumferential direction; and a third groove portion 53 which is isolated from the closed end 44b in the extending direction of the sipe 44. The first groove 51 and the second groove 52 are opened to the main groove 13. Since the land portion 20 and the groove wall of the main groove 13 are formed with the low land 13s at the groove edge, water is easily introduced from the main groove 13 into the sipe 44 and the shallow groove 50. The width of the lower stage 13s is, for example, 0.3 to 1.0mm. The depth of the lower stage 13s is, for example, 0.5 to 1.5mm. The depth of the low stage 13s is preferably equal to or greater than the trench depth D50 of the shallow trench 50.

The shallow trench 50 has a partition wall 54 provided between the first trench 51 and the third trench 53 and between the second trench 52 and the third trench 53. The shallow groove 50 is formed by a bead provided on a tire molding surface of a mold for vulcanization molding of the tire T, the bead having a shape divided at a position corresponding to the partition wall 54. Tire forming surfaces including lugs are typically made by casting aluminum. The protrusion is divided to have a short length, so that the protrusion can be prevented from rolling up and down due to shrinkage during casting, and the shallow trench 50 can be formed appropriately. In addition, the divided portions of the bead function as bypass passages through which air can circulate when the tire T is vulcanized, and therefore, it is advantageous to reduce the vulcanization molding failure.

The shallow grooves 50 do not have grooves curved in a tread plan view due to the partition walls 54. The first groove 51, the second groove 52, and the third groove 53 are each formed in a simple straight line or curved shape in a tread plan view without being bent. Therefore, air stagnation in the shallow trench 50 can be suppressed, and air column resonance can be reduced. The thickness T54 of the partition wall 54 is, for example, 0.5 to 1.0mm. In one example, the thickness T54 is 0.8mm. The partition wall 54 extends in the extending direction of the third groove 53, but is not limited to this, and may extend in the extending direction of the first groove 51 or the second groove 52, for example. The shallow trenches 50 may be configured without the partition walls 54.

In the present embodiment, the sipe 44 extends so as to be curved so as to gradually increase in angle with respect to the tire circumferential direction from the closed end 44b toward the open end 44 a. According to this structure, the sipe 44 can be connected to the main groove 13 at a proper angle, and the edges of the sipe 44 can be prevented from being grounded together when the tire T rotates, thereby reducing pattern noise. The sipe 44 has a shape in which a plurality of circular arcs having different radii of curvature are connected in a tread plan view. The tip portion of the sipe 44 including the closed end 44b is constituted by an arc of a relatively small radius of curvature, and the base portion of the sipe 44 including the open end 44a is constituted by an arc of a relatively large radius of curvature. However, the sipe 44 is not limited thereto, and may be formed of a single circular arc.

The first groove 51 and the second groove 52 are curved along the sipe 44. The first groove 51 located on the curved outer peripheral side of the sipe 44 extends in the tire circumferential direction beyond the closed end 44b of the sipe 44, and the third groove 53 extends obliquely with respect to the tire axial direction. The sipe 44 is not limited to a curved shape, and may be a straight extending shape, for example. The first groove 51 and the second groove 52 preferably have shapes that follow the sipe 44 in a tread plan view, but are not limited thereto. However, the above-mentioned interval G1 is preferably in the range of 0.8 to 1.5mm so that the shallow groove 50 is in a positional relationship that is not separated with respect to the sipe 44.

In the present embodiment, the low land 23s is provided at an acute angle portion formed by the sipe 44 and the shoulder main groove 13. Accordingly, it is possible to suppress toe wear of the heel in a form in which the sharp-angled portion having low rigidity is preferentially worn. The depth of the low stage 23s is, for example, 1.5 to 3.0mm. The depth of the low stage 23s is set to be equal to or greater than the depth of the low stage 13 s. The low stage 23s is formed in a triangular shape in a tread plan view. A chamfer, not shown, may be provided at the acute angle portion instead of the lower stage 23s. The chamfer is formed, for example, by an inclined surface gradually increasing in depth toward the tip of the acute angle portion.

Regarding the quarter land portions 23, the sipes 43 and the sipes 44 are arranged differently from each other in the tire circumferential direction, and they overlap in the tire circumferential direction view. The sipe 43 has a semi-closed configuration opening in the central main groove 12. The sipe 43 extends obliquely with respect to the tire axial direction. The sipe 43 is inclined in the same orientation as the base portion or third groove portion 53 of the sipe 44. In addition, a pit 60 is provided in the quarter land portion 23. The concave pit 60 is disposed between the sipe 43 and (the first groove 51 of) the shallow groove 50. By providing the concave recesses 60, the rigidity difference in the quarter land portion 23 can be reduced, and the rigidity balance can be improved.

The depth of the concave pits 60 is preferably equal to the depth of the end portion of the sipe 44 (the aforementioned depth D44 b), and more specifically, the ratio of the relatively small depth to the relatively large depth among them is preferably 80% or more, and more preferably 90% or more. According to this structure, the end portion of the sipe 44 and the concave pit 60 disappear by abrasion at substantially the same timing, so that the uneven wear state is inconspicuous in appearance. The concave pits 60 have a shape that becomes tapered in the extending direction of the sipe 44 in a tread plan view. Accordingly, the groove volume of the pit 60 can be reduced and the pattern noise caused by the pit 60 can be suppressed.

[ Quarter land portion of inner zone ]

As shown in fig. 7, the quarter land portion 22 and the quarter land portion 23 are adjacent in the tire axial direction across 1 central main groove 12. The quarter land portion 22 includes the sipe 42 and the sipe 32. The lateral groove 32 has a semi-closed configuration that opens at the shoulder main groove 11. That is, the cross groove 32 has: an open end 32a that opens in the shoulder main groove 11; and a closed end 32b closed within the land portion. The sipe 42 has a semi-closed configuration opening in the central main groove 12. That is, the sipe 42 has: an open end 42a that opens into the central main channel 12; and a closed end 42b closed within the land portion. The sipe 32 and the sipe 42 are disposed differently from each other in the tire circumferential direction, and overlap in the tire circumferential direction view.

Since the lateral grooves 32 and the sipes 42 are disposed differently from each other in the tire circumferential direction in the quarter land portion 22, the land portion rigidity (rib rigidity) can be made uniform, and uneven wear can be suppressed. From the viewpoint of the rigidity uniformity of the land portion, it is preferable that the interval G22 between the lateral groove 32 and the sipe 42 at the widthwise central position (central position of the maximum width) of the quarter land portion 22 is substantially constant. Specifically, the minimum value of the interval G22 is preferably 90% or more, more preferably 95% or more of the maximum value. The lateral groove 32 formed at the quarter land portion 22 to open at the shoulder main groove 11 helps to ensure drainage performance at the shoulder main groove 11 that does not communicate with the lateral groove 31.

The cross grooves 32 are formed so as to taper toward the closed end 32 b. Therefore, abrupt changes in the land rigidity can be suppressed, and the land rigidity of the tire equator TC side portion of the quarter land 22 can be easily ensured. The same applies to the lug grooves 31 included in the shoulder land portions 21. The sipe 32 is connected only to the shoulder main groove 11, and is not connected to the other sipe 30 and sipe 40. The sipe 42 is connected only to the central main groove 12, and is not connected to the other lateral grooves 30 and sipes 40. Only the lateral grooves 32 and the sipes 42 are formed in the quarter land portion 22.

The lug grooves 32 are curved so as to be convex in the tire circumferential direction. The cross grooves 32 are curved in a convex shape downward in fig. 7. The center of the circular arc passing through the center of the groove width of the lug groove 32 is located on one side (upper side in fig. 7) of the lug groove 32 in the tire circumferential direction. The sipe 42 is curved so as to be convex in the tire circumferential direction in the same direction as the lateral groove 32. According to this structure, abrupt changes in the interval between the lateral grooves 32 and the sipes 42 in the tire axial direction can be suppressed, and the land rigidity of the quarter land portion 22 can be uniformized.

The sipe 42 is smoothly continuous with respect to the sipe 43 across the main groove 10 (specifically, the central main groove 12). According to this structure, since the sipe 42 and the sipe 43 are moderately displaced in the tire circumferential direction, it is convenient to suppress the pattern noise. The 2 sipes 40 (or the lateral grooves 30) are smoothly continuous across the main groove 10: one virtual line extending in the longitudinal direction thereof and the other virtual line extending in the longitudinal direction thereof overlap in the main groove 10 or approach each other so that the separation distance in the tire circumferential direction is 10.0mm or less. In the example of fig. 7, virtual lines L42, L43 passing through the width centers of the sipes 42, 43 approach each other in the main groove 10.

[ Shoulder land portion ]

The shoulder land portion 21 includes a sipe 41 and a lateral groove 31. The lateral groove 31 is isolated from the main groove 10 and is not in communication with the shoulder main groove 11. The lug grooves 31 extend outward in the tire axial direction from closed ends 31a closed in land portions so as to cross the ground contact ends TE. The shoulder land portion 21 is not completely divided by the lateral groove 31. The shoulder land portions 21 are formed as ribs that extend continuously in the tire circumferential direction. The sipe 41 extends outward in the tire axial direction from an opening end 41a that opens in the shoulder main groove 11 so as to cross the land end TE. The sipes 40 other than the sipe 41 are not formed in the shoulder land portion 21. The sipe 31 and the sipe 41 are alternately arranged in the tire circumferential direction.

The lateral groove 31 is curved so as to be convex in the tire circumferential direction. The cross grooves 31 are curved so as to be convex downward in fig. 7. The center of the circular arc passing through the center of the groove width of the lug groove 31 is located on one side (upper side in fig. 7) of the lug groove 31 in the tire circumferential direction. The lug grooves 31 are curved in a convex shape in the tire circumferential direction in the same direction as the lug grooves 32. The sipe 41 is curved so as to be convex in the tire circumferential direction in the same direction as the lateral groove 31. According to this structure, abrupt changes in the interval between the lateral grooves 31 and the sipes 41 in the tire axial direction can be suppressed, and the land rigidity of the shoulder land portion 21 can be uniformized. The sipe 41 is curved in a convex shape in the tire circumferential direction in the same direction as the sipe 42.

The lug grooves 31 are smoothly continuous with respect to the lug grooves 32 across the main groove 10 (specifically, the shoulder main groove 11). According to this structure, since the lug grooves 31 and the lug grooves 32 are moderately displaced in the tire circumferential direction, it is convenient to suppress the pattern noise. In the example of fig. 7, virtual lines L31, L32 passing through the groove width centers of the lateral grooves 31, 32 overlap in the main groove 10. The sipe 41 is smoothly continuous with respect to the sipe 42 across the main groove 10 (specifically, the shoulder main groove 11). According to this structure, since the sipe 41 and the sipe 42 are moderately displaced in the tire circumferential direction, it is convenient to suppress the pattern noise. In the example of fig. 7, virtual lines L41, L42 passing through the width centers of the sipes 41, 42 overlap in the main groove 10.

From the viewpoint of suppressing uneven wear of the shoulder land portion 21, it is preferable that the interval G21 between the lateral groove 31 and the sipe 41 at the width center position (center position of maximum width) of the shoulder land portion 21 is substantially constant. Specifically, the minimum value of the interval G21 is preferably 55% or more, more preferably 85% or more, and still more preferably 90% or more of the maximum value. The width center position requirement for the shoulder land portion 21 is set as: a position half of the tire axial distance from the groove edge formed by the surface of the shoulder land portion 21 and the groove wall of the shoulder main groove 11 to the ground contact end TE.

As shown in fig. 2, the shoulder land portion 24 includes a sipe 45 and a lateral groove 33. The lug grooves 33 extend outward in the tire axial direction from an opening end 33a (see fig. 8) that opens in the shoulder main groove 13, and cross the ground contact end TE. The sipe 33 is curved so as to be convex in the tire circumferential direction in the same direction as the sipe 44. The center of the circular arc passing through the center of the groove width of the lug groove 33 is located on the other side (lower side in fig. 2) of the lug groove 33 in the tire circumferential direction. The sipe 33 is smoothly continuous with respect to the sipe 44 through the main groove 10 (specifically, the shoulder main groove 13). The sipe 45 is isolated from the shoulder main groove 13 and connected to the lateral groove 33. The sipe 33 and the sipe 45 are alternately arranged in the tire circumferential direction. The sipe 45 is curved so as to be convex in the tire circumferential direction in an opposite direction to the lateral groove 33.

As shown in fig. 8, in the present embodiment, at least in the region SA on the inner side in the tire axial direction of the land TE, the sipe 41 and the sipe 45 are offset in the tire circumferential direction so that the virtual line VL parallel to the tire axial direction intersecting the sipe 41 does not intersect the sipe 45. Fig. 8 shows 2 virtual lines VL. One of them passes through the open end 41a of the sipe 41, and the other passes through the intersection point of the sipe 41 and the land TE. The virtual line VL intersecting the sipe 41 in the region SA does not intersect the sipe 45 wherever it is set. In other words, the sipe 41 and the sipe 45 in the region SA do not overlap each other in the tire axial view.

In the present embodiment, the sipe 41 included in the shoulder land portion 21 and the sipe 45 included in the shoulder land portion 24 are convexly curved in the same direction in the tire circumferential direction, but they are offset in the tire circumferential direction as described above. Accordingly, the mode noise caused by the sipes 41 and 45 can be suppressed. In the present embodiment, the lateral groove 33 included in the shoulder land portion 24 of the outer region OUT is curved, and the sipe 45 is curved so as to be convex in the tire circumferential direction in the direction opposite to the direction of the lateral groove 33. Therefore, compared with the case of bending in the same direction, the frequency of the pitch noise is easily dispersed, and the pitch noise at the time of steering is suppressed.

It is preferable that the radius of curvature SR1 of the sipe 41 is different from the radius of curvature SR2 of the sipe 45. Accordingly, one sipe (sipe 41 in the present embodiment) has a relatively small degree of curvature and approximates a straight shape, and the other sipe (sipe 45 in the present embodiment) has a relatively large degree of curvature. In addition to the misalignment in the tire circumferential direction, the pattern noise caused by the sipes 41 and 45 can be effectively suppressed by making the curvatures different in this way. The difference between the radius of curvature SR1 and the radius of curvature SR2 is, for example, 60mm or more. The radii of curvature SR1, SR2 are set to: the radius of curvature of the circular arc passing through the center of the width of the sipe 41, 45 in the region SA.

In the present embodiment, the radius of curvature SR2 of the sipe 45 located on the vehicle outside when mounted on the vehicle is smaller than the radius of curvature SR1 of the sipe 41 located on the vehicle inside when mounted on the vehicle (SR 1 > SR 2). Accordingly, since the sipe 45 provided in the outer region OUT has an increased angle with respect to the tire circumferential direction at the outer portion in the tire axial direction, uneven wear can be suppressed.

In the present embodiment, the sipe 41 located on the vehicle inner side when mounted on the vehicle is connected to the main groove 10 (i.e., the shoulder main groove 11), and the sipe 45 located on the vehicle outer side when mounted on the vehicle is isolated from the main groove 10. Accordingly, the water is introduced from the shoulder main groove 11 into the shoulder land portion 21 IN the inner region IN by the sipe 41, and the water removing effect is also exerted, so that the water discharging performance is improved. The lateral groove 31 is not in communication with the main groove 10, and therefore, the sipe 41 is more advantageous in construction. In addition, in the shoulder land portion 24 of the outer region OUT, the decrease in the land portion rigidity due to the sipe 45 is suppressed, and therefore, it is convenient to ensure the steering stability performance at the time of cornering.

The sipe 41 and sipe 45 extend transversely across the land TE, and are connected to the concave portion 70 formed on the outer side in the tire axial direction than the land TE. Accordingly, the soft performance of the region between the adjacent sipes 31 and the region between the adjacent sipes 33 is enhanced, and the grounding performance of the shoulder land portions 21, 24 can be improved. The pit 70 has a maximum depth of, for example, 1.0mm or less. In one example, the depth of the concave pit 70 is 0.5mm at the outer end in the tire axial direction, gradually increases from this point toward the land TE, and is 0.8mm at the connecting portion with the sipe. The concave pit 70 is formed in a crescent shape having a relatively small width at both ends in the tire axial direction and a relatively large width at the center, but is not limited thereto.

In the present embodiment, the sipe 41 and the concave pit 70 form the first connecting body 71, the sipe 45 and the concave pit 70 form the second connecting body 72, and the first connecting body 71 and the second connecting body 72 are offset in the tire circumferential direction so that the virtual line VL' parallel to the tire axial direction intersecting the first connecting body 71 does not intersect the second connecting body 72. Accordingly, the mode noise caused by the sipes 41 and 45 can be suppressed more effectively. The virtual line VL' intersecting the first connecting body 71 does not intersect the second connecting body 72 wherever it is set. In other words, the first connecting body 71 and the second connecting body 72 do not overlap each other in the tire axial direction view.

[ Modification of tread Pattern ]

In the foregoing embodiment, the example in which 3 main grooves 10 are provided on the tread surface 3f has been shown, but the present invention is not limited thereto, and the number of main grooves 10 may be 2, 4, or 5 or more. Fig. 9 is an example in which 4 main grooves are provided on the tread surface 3f and 5 land portions 20 are partitioned by the 4 main grooves. The 4 main grooves 10 include a pair of shoulder main grooves 11, 13, and a pair of center main grooves 12, 14 therebetween. The 5 land portions 20 include a pair of shoulder land portions 21, 24, a pair of quarter land portions 22, 23, and a center land portion 25 formed between the pair of center main grooves 12, 14. The center land portion 25 is provided on the tire equator TC. In the center land portion 25, the lug grooves 34 and the lug grooves 35 are arranged differently from each other in the tire circumferential direction.

In the tire T of the present embodiment, at least 1 land portion includes the sipe described above and the shallow groove surrounding the sipe, and other than this, a conventionally known material, shape, structure, or the like may be employed, as in a normal pneumatic tire. The structures of land portions (shoulder land portions 21, 24, quarter land portion 22, and center land portion 25 in the present embodiment) other than the land portion (quarter land portion 23 in the present embodiment) including the sipe and the shallow groove surrounding the sipe as described above are not particularly limited, and various structures may be employed.

[1] As described above, the tire T of the present embodiment includes: a plurality of main grooves 10 extending in the tire circumferential direction at the tread surface 3 f; and a plurality of land portions 20 partitioned by the main groove 10, at least 1 land portion 20 (quarter land portion 23 in the present embodiment) including: a sipe 44; and shallow grooves 50 formed shallower than the sipes 44. The sipe 44 has: an open end 44a that opens in the main groove 10 (specifically, the shoulder main groove 13); and a closed end 44b closed within the land portion. The shallow groove 50 extends so as to surround the sipe 44 in a tread plan view, and is connected to the main groove 10 opened by the open end 44 a. With this structure, the water removal effect around the sipe 44 can be improved by the shallow grooves 50, and further, the drainage performance and the steering stability performance on a wet road surface can be improved.

[2] In addition to the tire T of [1], the depth of the shallow groove 50 is preferably 1.5mm or less. Accordingly, excessive movement around the edge of the sipe 44 can be suppressed, and deterioration of the grounding performance can be appropriately suppressed.

[3] In addition to the tire T of the above [1] or [2], it is preferable that the sipe 44 extends so as to be curved so as to gradually increase in angle with respect to the tire circumferential direction from the closed end 44b toward the open end 44 a. Accordingly, the sipe 44 is connected to the main groove 10 (shoulder main groove 13) at a proper angle, and the edges of the sipe 44 can be prevented from being grounded at the same time when the tire T rotates, so that pattern noise can be reduced.

[4] In addition to any one of the tires T of [1] to [3], the shallow groove 50 preferably has: a first groove 51 that is isolated from the sipe 44 on one side in the tire circumferential direction; a second groove portion 52 that is isolated from the sipe 44 on the other side in the tire circumferential direction; a third groove 53 which is isolated from the closed end 44b in the extending direction of the sipe 44; and a partition wall 54 provided between the first groove 51 and the third groove 53, and between the second groove 52 and the third groove 53. The partition wall 54 is useful for suppressing the ridge relief of the mold for forming the shallow trench 50, so that the shallow trench 50 can be formed appropriately.

[5] In addition to any one of the tires T described in [1] to [4], it is preferable that the low land 23s or the chamfer be provided at an acute angle portion formed by the sipe 44 and the main groove 10 (shoulder main groove 13). According to this structure, heel toe wear in a form in which the acute angle portion is preferentially worn can be suppressed.

Although the embodiment of the present invention has been described based on the drawings, it should be understood that the specific configuration is not limited to the embodiment. The scope of the present invention is shown by the claims, not by the description of the embodiments described above, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.

The tire of the present invention is not limited to the above embodiments, and is not limited to the above effects. The tire of the present invention may be modified and changed in various ways within a scope not departing from the gist thereof. The structures used in the above embodiments may be used in any combination.

Claims (10)

1. A tire, wherein the tire is formed of,

The tire is provided with: a plurality of main grooves extending in the tire circumferential direction on the tread surface; and a plurality of land portions defined by the main trench regions,

At least 1 of the land portions includes: a sipe; and shallow grooves formed shallower than the sipe,

The sipe has: an open end at the main trench opening; and a closed end closed within the land portion,

The shallow groove extends so as to surround the sipe in a tread plan view, and is connected to the main groove of the open-end opening.

2. The tire of claim 1, wherein,

The depth of the shallow trench is below 1.5 mm.

3. The tire of claim 1, wherein,

The sipe extends curvedly from the closed end toward the open end in such a manner that an angle with respect to the tire circumferential direction gradually increases.

4. The tire of claim 1, wherein,

The interval between the sipe and the shallow groove in the width direction of the sipe is 1.5mm or less.

5. The tire of claim 1, wherein,

The shallow trench has: a first groove portion that is isolated from the sipe on one side in the tire circumferential direction; a second groove portion that is isolated from the sipe on the other side in the tire circumferential direction; and a third groove portion isolated from the closed end in an extending direction of the sipe.

6. The tire of claim 5, wherein,

The shallow trench has a partition wall provided between the first trench and the third trench and between the second trench and the third trench.

7. The tire of claim 1, wherein,

The sipe has: a base portion extending at a relatively large depth from the open end toward the closed end; a tip portion extending from the closed end toward the open end to a relatively small depth; and an intermediate portion having a depth that gradually changes to join the base portion and the end portion.

8. The tire of claim 1, wherein,

The land portions including the sipes and the shallow grooves are provided as ribs extending continuously in the tire circumferential direction.

9. The tire of claim 1, wherein,

The assembly direction with respect to the vehicle is specified,

The sipe and the shallow groove are provided in an outer region on the vehicle outer side when the tire is mounted on the vehicle with reference to the tire equator.

10. Tyre according to any one of claims 1 to 9, wherein,

A low land or chamfer is provided at an acute angle portion formed by the sipe and the main groove.