JP7633484B2 - tire - Google Patents

Description

This invention relates to tires, and more specifically to tires that can achieve both wet and dry performance.

In recent years, sipes with chamfered openings on the tread surface, so-called chamfered sipes, have been adopted to improve the wet performance of tires. The technology described in Patent Document 1 is known as a conventional tire that adopts such a configuration.

JP 2018-111451 A

On the other hand, there is also the issue of improving the dry performance of tires.

Therefore, this invention was made in consideration of the above, and aims to provide a tire that can achieve both wet and dry performance.

In order to achieve the above object, a tire according to the present invention is a tire including two or more circumferential main grooves extending in a tire circumferential direction, and a pair of shoulder land portions and one or more rows of center land portions defined by the circumferential main grooves, the center land portion including a plurality of chamfered sipes that open at one end to an edge portion of the center land portion and terminate within the center land portion at the other end, and a plurality of thin through grooves that penetrate the center land portion in a tire width direction, the thin through grooves having a V-shape with an apex facing the tire circumferential direction and one side of the V-shape facing the chamfered sipes, and an inclination angle θ1 of a sipe portion of the chamfered sipe with respect to the tire circumferential direction and an inclination angle θ2 of the one side of the V-shape of the thin through groove are within a range of -10 a maximum distance Db_max from a center line of a sipe portion of the remote chamfered sipe to a center line of the through-thickness fine groove is in the range of 1.50≦Db_max/Da_max≦12.0, wherein the inclination angle θ1 of the chamfered sipe with respect to the circumferential direction of the tire is in the range of 30 [deg]≦θ1≦60 [deg], a single narrow through-groove is disposed between a pair of the chamfered sipes adjacent to each other in the circumferential direction of the tire, and a nearby chamfered sipe disposed close to the nearby through-thickness fine groove and a remote chamfered sipe disposed far from the nearby through-thickness fine groove are defined, and a maximum distance Db_max from a center line of a sipe portion of the remote chamfered sipe to a center line of the through-thickness fine groove is in the range of 1.50≦Db_max/Da_max≦12.0, wherein the maximum distance Da_max from the center line of the sipe portion of the nearby chamfered sipe to the center line of the through-thickness fine groove is in the range of 1.50≦Db_max/Da_max≦12.0 .
The tire according to the present invention is a tire including two or more circumferential main grooves extending in the tire circumferential direction, and a pair of shoulder land portions and one or more rows of center land portions defined by the circumferential main grooves, the center land portion including a plurality of chamfered sipes that open at one end to an edge portion of the center land portion and terminate within the center land portion at the other end, and a plurality of thin through grooves that penetrate the center land portion in the tire width direction, the thin through grooves having a V-shape with an apex facing the tire circumferential direction and one side of the V-shape facing the chamfered sipe, and a front side of the ... The inclination angle θ1 of the sipe portion of the chamfered sipe and the inclination angle θ2 of one side of the V-shape of the fine through-groove have a relationship of -10 [deg]≦θ1-θ2≦10 [deg], the inclination angle θ1 of the chamfered sipe with respect to the tire circumferential direction is in the range of 30 [deg]≦θ1≦60 [deg], and the apex of the V-shape of the fine through-groove is positioned offset in the tire width direction with respect to the center line of the central land portion, so that the open end of the chamfered sipe is positioned in one region bounded by the center line of the central land portion, and the apex of the V-shape of the fine through-groove is positioned in the other region.
Further, a tire according to the present invention is a tire including two or more circumferential main grooves extending in a tire circumferential direction, and a pair of shoulder land portions and one or more rows of center land portions defined by the circumferential main grooves, the center land portion including a plurality of chamfered sipes that open at one end to an edge portion of the center land portion and terminate within the center land portion at the other end, and a plurality of thin through grooves that penetrate the center land portion in the tire width direction, the thin through grooves having a V-shape with an apex facing the tire circumferential direction and one side of the V-shape facing the chamfered sipes, and the size of the chamfered sipes relative to the tire circumferential direction is determined by the circumferential direction of the tire. the inclination angle θ1 of the chamfered sipe portion and the inclination angle θ2 of one side of the V-shape of the fine through-groove have a relationship of -10 degrees≦θ1-θ2≦10 degrees, the inclination angle θ1 of the chamfered sipe with respect to the circumferential direction of the tire is in the range of 30 degrees≦θ1≦60 degrees, the tire is provided with first and second groove units consisting of the chamfered sipe and the fine through-groove, the chamfered sipe of the first groove unit opens to one edge portion of the center land portion and the chamfered sipe of the second groove unit opens to the other edge portion of the center land portion, and the first groove units and the second groove units are arranged alternately in the circumferential direction of the tire.
The tire according to the present invention is a tire including two or more circumferential main grooves extending in the tire circumferential direction, a pair of shoulder land portions and one or more rows of center land portions defined by the circumferential main grooves, the center land portion including a plurality of chamfered sipes that open at one end to an edge portion of the center land portion and terminate within the center land portion at the other end, and a plurality of thin through grooves that penetrate the center land portion in the tire width direction, the thin through grooves having a V-shape with an apex facing in the tire circumferential direction. and one side of the V-shape is arranged opposite the chamfered sipe, an inclination angle θ1 of the sipe portion of the chamfered sipe with respect to the tire circumferential direction and an inclination angle θ2 of the one side of the V-shape of the fine through-groove have a relationship of -10 [deg]≦θ1-θ2≦10 [deg], the inclination angle θ1 of the chamfered sipe with respect to the tire circumferential direction is in the range of 30 [deg]≦θ1≦60 [deg], and the fine through-grooves adjacent in the tire circumferential direction are arranged so that the V-shapes face in opposite directions to each other.

In the tire according to the present invention, (1) the through-thin grooves are arranged opposite the chamfered sipes, so that the through-thin grooves are actively closed when the tire touches the ground, dispersing the ground pressure to the chamfered sipes. This suppresses the crushing of the chamfered portion of the chamfered sipes and ensures the drainage of the chamfered portion. This ensures the wet performance of the tire. Furthermore, (2) one side of the V-shape of the through-thin grooves is arranged approximately parallel to the sipe portion of the chamfered sipes, so that the crushing of the chamfered portion of the chamfered sipes is effectively suppressed. This effectively improves the wet performance of the tire. Also, (3) the chamfered sipes have a semi-closed structure that terminates within the center land portion, so that the rigidity of the center land portion is ensured, and the steering stability of the tire on dry road surfaces is improved. Also, (4) the through-thin grooves have a V-shape, so that the rigidity of the center land portion is ensured. As a result, the deformation of the center land portion when the tire touches the ground is suppressed, and the steering stability of the tire on dry road surfaces is improved. The above (1) to (4) have the advantage that the tire's wet performance and steering stability on dry roads are compatible.

FIG. 1 is a cross-sectional view in the tire meridian direction showing a tire 1 according to an embodiment of the present invention. FIG. 2 is a plan view showing the tread surface of the tire shown in FIG. FIG. 3 is an enlarged view showing the center land portion of the tire shown in FIG. FIG. 4 is an enlarged view showing the first groove unit of the center land portion shown in FIG. FIG. 5 is a longitudinal cross-sectional view showing the chamfered sipe of the first groove unit shown in FIG. FIG. 6 is a longitudinal cross-sectional view of the through groove of the first groove unit shown in FIG. FIG. 7 is a cross-sectional view in the width direction showing the chamfered sipe and the thin through groove of the first groove unit shown in FIG. FIG. 8 is an enlarged view showing the second groove unit of the center land portion shown in FIG. FIG. 9 is a table showing the results of performance tests of the tire according to the embodiment of the present invention. FIG. 10 is a table showing the results of performance tests of the tire according to the embodiment of the present invention.

The present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to these embodiments. The components of the embodiments include those that can be substituted and are obvious substitutes while maintaining the identity of the invention. The multiple modified examples described in the embodiments can be combined in any way that is obvious to those skilled in the art.

[tire]
Fig. 1 is a cross-sectional view in the tire meridian direction showing a tire 1 according to an embodiment of the present invention. The figure shows a cross-sectional view of one side region in the tire radial direction. In this embodiment, a pneumatic radial tire for passenger cars will be described as an example of a tire.

In the figure, the tire meridian cross section is defined as a cross section of the tire cut by a plane including the tire rotation axis (not shown). The tire equatorial plane CL is defined as a plane that passes through the midpoint of the tire cross-sectional width defined by JATMA and is perpendicular to the tire rotation axis. The tire width direction is defined as the direction parallel to the tire rotation axis, and the tire radial direction is defined as the direction perpendicular to the tire rotation axis.

The inner and outer sides of the vehicle width direction are defined as the directions relative to the vehicle width direction when the tire is mounted on the vehicle. The left and right regions bounded by the tire equatorial plane are defined as the outer and inner regions of the vehicle width direction, respectively. The tire also has a mounting direction indicator (not shown) that indicates the direction in which the tire is mounted on the vehicle. The mounting direction indicator is, for example, configured by a mark or unevenness on the sidewall of the tire. For example, ECER 30 (Article 30 of the Economic Commission for Europe Regulation) requires that a vehicle mounting direction indicator be provided on the sidewall that is on the outer side in the vehicle width direction when mounted on the vehicle.

The tire 1 has an annular structure centered on the tire rotation axis, and includes a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, 16, and a pair of rim cushion rubbers 17, 17 (see Figure 1).

The pair of bead cores 11, 11 are made by winding one or more steel bead wires in a circular shape in multiple layers, and are embedded in the bead portions to form the cores of the left and right bead portions. The pair of bead fillers 12, 12 are arranged on the outer periphery of the pair of bead cores 11, 11 in the tire radial direction, respectively, to reinforce the bead portions.

The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass plies stacked together, and is toroidally stretched between the left and right bead cores 11, 11 to form the tire's framework. In addition, both ends of the carcass layer 13 are wrapped around and secured to the outside in the tire width direction so as to envelop the bead cores 11 and the bead fillers 12. In addition, the carcass ply of the carcass layer 13 is formed by coating multiple carcass cords made of steel or organic fiber material (e.g., aramid, nylon, polyester, rayon, etc.) with coating rubber and rolling them, and has a cord angle (defined as the inclination angle of the carcass cords in the longitudinal direction relative to the tire circumferential direction) of 80 degrees or more and 100 degrees or less.

The belt layer 14 is made by laminating multiple belt plies 141 to 143 and is arranged around the outer periphery of the carcass layer 13. The belt plies 141 to 143 include a pair of cross belts 141, 142 and a belt cover 143.

The pair of cross belts 141, 142 are formed by coating multiple belt cords made of steel or organic fiber material with coating rubber and rolling them, and have a cord angle of 15 degrees or more and 55 degrees or less in absolute value. The pair of cross belts 141, 142 have cord angles of opposite signs (defined as the inclination angle of the belt cords in the longitudinal direction with respect to the tire circumferential direction), and are layered with the belt cords' longitudinal directions crossing each other (so-called cross-ply structure). The pair of cross belts 141, 142 are layered and arranged on the outer side of the carcass layer 13 in the tire radial direction.

The belt cover 143 is formed by covering a belt cover cord made of steel or organic fiber material with coating rubber, and has a cord angle of 0 degrees or more and 10 degrees or less in absolute value. The belt cover 143 is, for example, a strip material formed by covering one or more belt cover cords with coating rubber, and is formed by winding this strip material spirally around the outer circumferential surfaces of the cross belts 141 and 142 multiple times in the tire circumferential direction. The belt cover 143 is disposed to cover the entire area of the cross belts 141 and 142.

The tread rubber 15 is arranged on the tire radial outer circumference of the carcass layer 13 and the belt layer 14 to form the tread portion of the tire 1. A pair of sidewall rubbers 16, 16 are arranged on the tire widthwise outer sides of the carcass layer 13 to form the left and right sidewall portions. A pair of rim cushion rubbers 17, 17 extend from the tire radial inner side of the left and right bead cores 11, 11 and the turned-up portion of the carcass layer 13 to the tire widthwise outer side to form the rim fitting surface of the bead portion.

[Tread surface]
Fig. 2 is a plan view showing the tread surface of the tire 1 shown in Fig. 1. The figure shows the tread surface of a summer tire. In the figure, the tire circumferential direction refers to the direction around the tire rotation axis. Also, the symbol T indicates the tire ground contact end, and the dimension symbol TW indicates the tire ground contact width.

As shown in FIG. 2, the tire 1 has three circumferential main grooves 21-23 and four rows of land portions 31-34 defined by these circumferential main grooves 21-23 on the tread surface.

The circumferential main grooves 21-23 are grooves that extend in the circumferential direction of the tire and have a continuous annular structure around the entire circumference of the tire. Each of the circumferential main grooves 21-23 is a main groove that is required to display a wear indicator as stipulated by JATMA, and has a maximum groove width of 3.0 mm or more and a maximum groove depth of 5.0 mm or more.

Groove width is measured as the distance between the opposing groove walls at the groove opening when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. In configurations where the groove opening has a notch or chamfer, the groove width is measured using the intersection of an extension of the tread surface and an extension of the groove wall in a cross-sectional view parallel to the groove width direction and the groove depth direction as the endpoint.

Groove depth is measured as the distance from the tread surface to the bottom of the groove when the tire is mounted on a specified rim, inflated to the specified internal pressure, and in an unloaded state. In addition, for configurations that have partial unevenness or sipes at the bottom of the groove, the groove depth is measured excluding these.

The specified rim refers to the "standard rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. The specified internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "inflation pressures" specified by ETRTO. The specified load refers to the "maximum load capacity" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "load capacity" specified by ETRTO. However, in JATMA, for passenger car tires, the specified internal pressure is 180 kPa, and the specified load is 88% of the maximum load capacity at the specified internal pressure.

In addition, in FIG. 2, of the multiple circumferential main grooves 21-23, the circumferential main grooves 21, 23 located on the outermost sides in the tire width direction are defined as shoulder main grooves. The shoulder main grooves are defined as left and right regions bounded by the tire equatorial plane CL. The circumferential main groove 22, which is closer to the tire equatorial plane CL than the shoulder main groove, is defined as the center main groove.

In the configuration shown in FIG. 2, the maximum groove width of the center main groove 22 (dimension symbols omitted in the figure) is wider than the maximum groove widths of the shoulder main grooves 21 and 23 (dimension symbols omitted in the figure). In addition, the sum of the groove widths of the circumferential main grooves is in the range of 10% to 30% of the tire contact width. This improves the drainage of the center region of the tread.

In addition, in the configuration shown in FIG. 2, the distance from the tire equatorial plane CL to the groove center lines of the left and right shoulder main grooves 21, 23 (dimension symbols omitted in the figure) is in the range of 26% to 32% of the tire contact width TW.

The groove centerline is defined as an imaginary line connecting the midpoints of the distance between opposing groove walls.

The tire contact width TW is measured as the maximum linear distance in the axial direction of the tire at the contact surface between the tire and a flat plate when the tire is mounted on a specified rim, pressurized to the specified internal pressure, and placed perpendicular to a flat plate in a stationary state and subjected to a load corresponding to a specified load.

The tire ground contact edge T is defined as the maximum axial width position of the contact surface between the tire and a flat plate when the tire is mounted on a specified rim, pressurized to a specified internal pressure, and placed perpendicular to a flat plate in a stationary state and subjected to a load corresponding to a specified load.

In the configuration shown in FIG. 2, the left and right regions bounded by the tire equatorial plane CL each have shoulder main grooves 21, 23, and these shoulder main grooves 21, 23 are arranged symmetrically with the tire equatorial plane CL as the center. The center main groove 22 is also arranged on the tire equatorial plane CL. These circumferential main grooves 21-23 define four rows of land portions 31-34.

However, this is not limiting, and two or four or more circumferential main grooves may be arranged, and the circumferential main grooves may be arranged asymmetrically with respect to the tire equatorial plane CL (not shown). In addition, the circumferential main grooves may be arranged away from the tire equatorial plane CL, so that the land portion is arranged on the tire equatorial plane CL (not shown).

In addition, in FIG. 2, of the multiple land portions 31-34, the land portions 31, 34 on the outer side in the tire width direction, defined by the shoulder main grooves 21, 23, are defined as shoulder land portions, and the land portions 32, 33 on the inner side in the tire width direction are defined as center land portions. In a configuration with three circumferential main grooves 21-23 as in FIG. 2, a pair of shoulder land portions 31, 34 and a pair of center land portions 32, 33 are defined. Also, for example, in a configuration with two circumferential main grooves, a single center land portion is defined, and in a configuration with four or more circumferential main grooves, three or more rows of center land portions are defined (not shown).

In addition, in FIG. 2, the maximum ground contact width Wb of each of the center land portions 32 and 33 is in the range of 0.10≦Wb/TW≦0.30 with respect to the tire ground contact width TW.

The contact width of the land portion is measured as the linear distance in the axial direction of the tire at the contact surface between the land portion and the flat plate when the tire is mounted on a specified rim, pressurized to the specified internal pressure, and placed perpendicular to a flat plate in a stationary state and subjected to a load corresponding to the specified load.

[Center Land Area]
FIG. 3 is an enlarged view showing the center land portion 32, 33 of the tire 1 shown in FIG. 2. FIG. 4 is an enlarged view showing the first groove unit UA of the center land portion 32 (33) shown in FIG. 3. FIG. 5 is a longitudinal cross-sectional view showing the chamfered sipe 321A of the first groove unit UA shown in FIG. 4, and FIG. 6 is a longitudinal cross-sectional view showing the through-thin groove 322A of the first groove unit UA shown in FIG. 4. FIG. 7 is a widthwise cross-sectional view showing the chamfered sipe 321A and the through-thin groove 322A of the first groove unit UA shown in FIG. 4. FIG. 8 is an enlarged view showing the second groove unit UB of the center land portion 32 (33) shown in FIG. 3. The configurations of the chamfered sipe 321B and the through-thin groove 322B of the second groove unit UB shown in FIG. 3 are the same as those of the chamfered sipe 321A and the through-thin groove 322A of the first groove unit UA shown in FIGS. 5 to 7, and therefore are omitted from the illustration.

In the configuration of FIG. 2, each of the two rows of center land portions 32, 33 has a plurality of first groove units UA consisting of first chamfered sipes 321A; 331A and first narrow through grooves 322A; 332A, and a plurality of second groove units UB consisting of second chamfered sipes 321B; 331B and second narrow through grooves 322B; 332B. Here, since the two rows of center land portions 32, 33 have the same structure, as an example, the groove units UA, UB of the center land portion 32 on the outer side in the vehicle width direction will be described in detail, and the groove units UA, UB of the center land portion 33 on the inner side in the vehicle width direction will be omitted.

As shown in FIG. 3, the chamfered sipes 321A, 321B open at one end to an edge of the center land portion 32 and terminate at the other end within the center land portion 32. The first chamfered sipe 321A of the first groove unit UA opens at one edge of the center land portion 32, and the second chamfered sipe 321B of the second groove unit UB opens at the other edge of the center land portion 32. The first and second groove units UA, UB are alternately arranged in the tire circumferential direction, so that the first and second chamfered sipes 321A, 321B are arranged in a staggered pattern in the tire circumferential direction.

In addition, in Figures 4 and 8, the first and second chamfered sipes 321A and the second chamfered sipes 321B each have a sipe portion 3211 and a chamfered portion 3212.

The sipe portion 3211 is a cut formed on the tread surface and has a maximum width W11 of 0.5 mm to 1.5 mm (see Figures 4 and 8) and a maximum depth H11 of 2.0 mm or more and less than the maximum groove depth Hg of the circumferential main groove 21 (see Figure 5).

The sipes in the sipe section are measured as the opening width of the sipes on the tread surface when the tire is mounted on a specified rim, inflated to the specified internal pressure, and in an unloaded state.

The depth of the sipes is measured as the distance from the tread surface to the bottom of the sipe when the tire is mounted on a specified rim, inflated to the specified internal pressure, and in an unloaded state.

The chamfered portion 3212 is formed on at least one edge of the sipe portion 3211 on the tread surface, and connects the tread surface and the wall surface of the sipe portion 3211 with a flat or curved surface. The chamfered portion 3212 is defined as having a maximum width (dimension symbols omitted in the figure) and maximum depth H12 (see FIG. 5) of 1.0 mm or more, and does not include a minute edge processing portion having a maximum width and maximum depth of less than 1.0 mm. In the configuration of FIG. 7, the chamfered portion 3212 is a so-called C chamfer, but the shape of the chamfered portion 3212 can be appropriately selected within the scope of obvious to a person skilled in the art. The maximum depth H12 of the chamfered portion 3212 is in the range of 0.10≦H12/H11≦0.85 with respect to the maximum depth H11 of the sipe portion 3211, and preferably in the range of 0.20≦H12/H11≦0.50.

The depth of the chamfer 3212 is measured as the distance from the tread surface to the boundary between the chamfer 3212 and the sipe 3211 when the tire is mounted on a specified rim, inflated to the specified internal pressure, and in an unloaded state.

4 and 8, the maximum width W1 of the chamfered sipes 321A and 321B, i.e., the maximum value of the total width of the sipe portion 3211 and the chamfered portion 3212, is in the range of 2.00≦W1/W11≦6.00 with respect to the maximum width W11 of the sipe portion 3211. Also, in FIG. 5, the maximum depth H1 of the chamfered sipes 321A and 321B is in the range of 0.40≦H1/Hg≦0.80 with respect to the maximum groove depth Hg of the circumferential main groove 21. The maximum depth H1 of the chamfered sipes 321A and 321B is equal to the maximum depth H11 of the sipe portion 3211.

The width of the chamfered sipes 321A, 321B is measured as the opening width of the chamfered sipes 321A, 321B in a direction perpendicular to the longitudinal direction of the sipe portion 3211 on the tread surface when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.

For example, in the configurations of Figures 4 and 8, the chamfered sipes 321A, 321B have a so-called one-sided chamfered structure, and have a chamfered portion 3212 only on one edge of the sipe portion 3211. Also, the chamfered portion 3212 of the chamfered sipe 321A is formed on the edge portion on the side of the thin through grooves 322A, 322B, which will be described later, of the left and right edges of the sipe portion 3211. This improves the ground contact characteristics of the center land portion 32. However, this is not limited to this, and the chamfered portion 3212 may be formed on each of the left and right edges of the sipe portion 3211 (not shown).

In the configurations of Figs. 4 and 8, the chamfered sipes 321A and 321B have a straight line shape. However, the chamfered sipes 321A and 321B may have, for example, a gentle arc shape or an S-shape (not shown). In the configurations of Figs. 4 and 8, the chamfered portion 3212 is formed over the entire longitudinal area of the sipe portion 3211. However, the chamfered portion 3212 may be formed over a portion of the longitudinal direction of the sipe portion 3211, more specifically, over 60% or more of the longitudinal direction, preferably over 80% or more of the longitudinal direction. In this case, as shown in Figs. 4 and 8, the chamfered portion 3212 must open to the edge portion of the center land portion 32. This ensures that the chamfered portion 3212 improves drainage.

4 and 8, the inclination angle θ1 of the sipe portion 3211 of the chamfered sipes 321A and 321B relative to the tire circumferential direction is in the range of 30 [deg]≦θ1≦60 [deg], preferably in the range of 35 [deg]≦θ1≦55 [deg], and more preferably in the range of 40 [deg]≦θ1≦50 [deg]. The difference between the inclination angles θ1, θ1 of the chamfered sipes 321A and 321B adjacent to each other in the tire circumferential direction is in the range of -5 [deg] or more and 5 [deg] or less. Therefore, the chamfered sipes 321A and 321B adjacent to each other in the tire circumferential direction are arranged substantially parallel and in a staggered pattern.

The inclination angle θ1 of the chamfered sipes 321A, 321B is measured as the angle between an imaginary line passing through both ends of the sipe portion 3211 of the chamfered sipes 321A, 321B and the tire circumferential direction.

In addition, in Figures 4 and 8, the extension distance D11 of the chamfered sipes 321A and 321B sipe portion 3211 in the tire width direction is in the range of 0.40 ≦ D11/Wb ≦ 0.90 with respect to the maximum contact width Wb of the center land portion 32, and preferably in the range of 0.60 ≦ D11/Wb ≦ 0.80.

The extension distance D11 of the sipe portion 3211 is measured as the distance in the tire width direction from the edge of the center land portion 32 to the end of the sipe portion 3211 when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.

In addition, in FIG. 3, the circumferential distance P2' between adjacent chamfered sipes 321A and 321B in the tire circumferential direction is in the range of 0.35≦P2'/P2≦0.65 with respect to the pitch length P2 of the first chamfered sipe 321A, and preferably in the range of 0.40≦P2'/P2≦0.60. Therefore, the first chamfered sipe 321A and the second chamfered sipe 321B are arranged at approximately equal intervals in the tire circumferential direction.

The circumferential distance P2' of the chamfered sipes 321A, 321B is measured by drawing imaginary straight lines passing through both ends of the sipe portion 3211 of the chamfered sipes 321A, 321B, and measuring the distance in the tire circumferential direction from the intersection of these imaginary lines with the center line of the center land portion 32 (see Figure 4).

As shown in FIG. 3, the thin through grooves 322A and 322B have a V-shape or an L-shape and penetrate the center land portion 32 in the tire width direction. The thin through grooves 322A and 322B are arranged with the apex T1 of the V-shape (see FIG. 4) facing the tire circumferential direction. Specifically, the two sides constituting the V-shape are inclined in opposite directions to each other with respect to the tire circumferential direction, so that the apex T1 of the V-shape protrudes in one direction in the tire circumferential direction. The first thin through groove 322A of the first groove unit UA has a V-shape that is convex on one side in the tire circumferential direction (downward in the figure), and the second thin through groove 322B of the second groove unit UB has a V-shape that is convex on the other side in the tire circumferential direction (upward in the figure). The first and second groove units UA and UB are arranged alternately in the tire circumferential direction, so that the first and second thin through grooves 322A and 322B are arranged with the convex direction of the V-shape alternately reversed.

As shown in FIG. 3, the narrow through grooves 322A and 322B are arranged with one side of the V-shape facing the nearby chamfered sipes 321A and 321B. The first narrow through groove 322A of the first groove unit UA is arranged with the convex side of the V-shape facing the first chamfered sipe 321A, and the second narrow through groove 322B of the second groove unit UB is arranged with the concave side of the V-shape facing the second chamfered sipe 321B. The first and second groove units UA and UB are arranged alternately in the tire circumferential direction, so that the first narrow through groove 322A with the convex side of the V-shape facing the first chamfered sipe 321A and the second narrow through groove 322B with the concave side of the V-shape facing the second chamfered sipe 321B are arranged alternately in the tire circumferential direction.

4 and 8, the inclination angle θ2 of one side of the V-shape of the through groove 322A; 322B (i.e., the side facing the chamfered sipes 321A, 321B) has a relationship of -10 [deg] ≦ θ1 - θ2 ≦ 10 [deg] with respect to the inclination angle θ1 of the chamfered sipes 321A; 321B, and preferably has a relationship of -5 [deg] ≦ θ1 - θ2 ≦ 5 [deg]. Therefore, the one side of the V-shape of the through groove 322A; 322B is disposed approximately parallel to the chamfered sipes 321A; 321B.

The inclination angle θ2 of one side of the V-shape is measured as the angle between the tire circumferential direction and an imaginary line passing through the intersection of the groove centerline of one side with the edge of the center land portion 32 and the apex T1 of the V-shape.

In the above configuration, (1) the fine through grooves 322A, 322B are arranged opposite the chamfered sipes 321A, 321B, so that the fine through grooves 322A, 322B are actively closed when the tire touches the ground, dispersing the ground pressure to the chamfered sipes 321A, 321B. As a result, compared to a configuration with only chamfered sipes (not shown), crushing of the chamfered portions 3212 of the chamfered sipes 321A, 321B is suppressed, ensuring the drainage function of the chamfered portions 3212. This ensures the wet performance of the tire. Furthermore, (2) one side of the V-shaped through-groove 322A, 322B (particularly the sipe portion 3221 in FIG. 4 and FIG. 8) is arranged approximately parallel (-10 [deg] ≦ θ1-θ2 ≦ 10 [deg]) to the sipe portion 3211 of the chamfered sipe 321A, 321B, so that the crushing of the chamfered portion 3212 of the chamfered sipe 321A, 321B is effectively suppressed compared to a configuration in which the two are not parallel (not shown). This effectively improves the wet performance of the tire. Also, (3) since the chamfered sipe 321A, 321B has a semi-closed structure that terminates within the center land portion 32, 33, the rigidity of the center land portion 32, 33 is ensured, and the steering stability performance of the tire on a dry road surface is improved compared to a configuration (not shown) having a chamfered sipe of an open structure that penetrates the land portion. In addition, (4) since the thin through grooves 322A, 322B have a V-shape, the rigidity of the center land portions 32, 33 is ensured compared to a configuration with straight-line thin through grooves (not shown). This suppresses deformation of the center land portions 32, 33 when the tire touches the ground, improving the steering stability of the tire on dry roads. The above (1) to (4) allow the tire to achieve both wet performance and steering stability on dry roads.

In addition, in Figures 4 and 8, the bending angle α of the V-shaped through grooves 322A and 322B is in the range of 80 [deg] ≦ α ≦ 150 [deg], and preferably in the range of 95 [deg] ≦ α ≦ 105 [deg].

The bending angle α of the V-shape is measured as the angle between two imaginary straight lines connecting the apex T1 of the V-shape of the through grooves 322A and 322B to the left and right opening ends.

The distance Da from one side of the V-shape of the through groove 322A; 322B to the sipe portion 3211 of the chamfered sipe 321A; 321B is in the range of 0.20≦Da/W11≦30 with respect to the maximum width W11 (see FIG. 4 and FIG. 8) of the sipe portion 3211 of the chamfered sipe 321A; 321B, and preferably in the range of 3.0≦Da/W11≦20. The distance Da is in the range of 0.05≦Da/Wb≦1.00 with respect to the maximum ground contact width Wb of the center land portion 32, and preferably in the range of 0.15≦Da/Wb≦0.50. It is preferable that the distance Da is in the range of 4.0 [mm]≦Da≦15.0 [mm]. In addition, 60% or more of the longitudinal length of the sipe portion 3211 of the chamfered sipes 321A; 321B must satisfy the above-mentioned distance Da condition.

The distance Da is measured from the groove centerline of the sipe portion 3211 of the chamfered sipe 321A; 321B to the groove centerline of one side of the V-shape of the through-thin groove 322A; 322B.

Also, as shown in Fig. 3, a single narrow through groove 322A; 322B is disposed between a pair of chamfered sipes 321A, 321B adjacent to each other in the tire circumferential direction. Here, the pair of chamfered sipes 321A, 321B are defined as adjacent chamfered sipes 321A; 321B disposed near the narrow through groove 322A; 322B, and remote chamfered sipes 321B; 321A disposed far from the narrow through groove 322A; 322B. In the configuration of Fig. 3, the first narrow through groove 322A of the first groove unit UA is defined as the adjacent narrow through groove to the first chamfered sipe 321A of the first groove unit UA, and the second narrow through groove 322B of the second groove unit UB is defined as the remote narrow through groove . Similarly, the second through slot 322B of the second groove unit UB is defined as the adjacent through slot to the second chamfered sipe 321B of the second groove unit UB, and the first through slot 322A of the first groove unit UA is defined as the remote through slot .

In this case, the maximum value Db_max of the distance Db from the center line of the sipe portion 3211 (see Figures 4 and 8) of the remote chamfered sipe 321B; 321A to the center line of the through groove 322A; 322B is in the range of 1.50≦Db_max/Da_max≦12.0, and preferably in the range of 2.00≦Db_max/Da_max≦6.00, relative to the maximum value Da_max of the distance Da from the center line of the sipe portion 3211 of the proximal chamfered sipe 321A; 321B to the center line of the through groove 322A; 322B. In this configuration, the through-thin grooves 322A; 322B are biased between a pair of adjacent chamfered sipes 321A, 321B, which effectively prevents the chamfered portion 3212 of the adjacent chamfered sipes 321A; 321B from being crushed, improving the wet performance of the tire, and at the same time, the contact area from the through-thin grooves 322A; 322B to the remote chamfered sipes 321B; 321A is secured, improving the dry steering stability of the tire.

For example, in the configuration of FIG. 3, as described above, the first and second groove units UA and UB are alternately arranged in the tire circumferential direction, and the first and second narrow through grooves 322A and 322B are alternately arranged with the convex direction of the V-shape reversed. Also, the first groove unit UA has the first chamfered sipe 321A on the convex side of the V-shape of the first narrow through groove 322A, and the second groove unit UB has the second chamfered sipe 321B on the concave side of the V-shape of the second narrow through groove 322B, so that the chamfered sipes 321A and 321B and the narrow through grooves 322A and 322B are alternately arranged in the tire circumferential direction. Also, the first and second groove units UA and UB are arranged at a predetermined interval in the tire circumferential direction, so that a pair of chamfered sipes 321A and 321B adjacent to each other in the tire circumferential direction are arranged at different distances Da and Db from one narrow through groove 322A; 322B.

As shown in FIG. 4 and FIG. 8, the apex T1 of the V-shape is offset in the tire width direction from the center line of the center land portion 32. The distance Dt from the center line of the center land portion 32 to the apex T1 of the V-shape of the through-thin grooves 322A and 322B is in the range of 0.10≦Dt/Wb≦0.40 with respect to the maximum ground contact width Wb of the center land portion 32, and preferably in the range of 0.25≦Dt/Wb≦0.75. In this configuration, the apex T1 of the V-shape of the through-thin grooves 322A and 322B is disposed in the region opposite the main body of the chamfered sipes 321A and 321B in the tire width direction, so that the extension length of the one side of the V-shape facing the chamfered sipes 321A and 321B can be extended. This effectively suppresses the crushing of the chamfered portion 3212 of the chamfered sipes 321A and 321B.

4 and 8, the V-shaped apex T1 of the through grooves 322A and 322B and the open ends of the chamfered sipes 321A and 321B relative to the circumferential main groove 21 are located in different regions that are bounded by the center line of the center land portion 32. Therefore, the V-shaped apex T1 of the through grooves 322A and 322B is located in the region opposite the chamfered sipes 321A and 321B in the tire width direction. Also, in the configurations of FIG. 4 and FIG. 8, the V-shaped apex T1 of the through grooves 322A and 322B is offset in the tire width direction relative to the end of the chamfered sipes 321A and 321B in the center land portion 32. This makes the rigidity of the center land portion 32 uniform in the tire width direction.

For example, in the configuration of FIG. 3, the first through narrow groove 322A of the first groove unit UA and the second through narrow groove 322B of the second groove unit UB have a V-shape formed by connecting the long and short sides, and have a structure that is point-symmetrical with respect to each other. Also, as described above, the first and second groove units UA and UB are arranged alternately in the tire circumferential direction. Therefore, the apexes T1 of the V-shapes of adjacent through narrow grooves 322A and 322B are biased in opposite directions to each other in the tire width direction.

In addition, in the configuration of FIG. 3, as shown in FIG. 4 and FIG. 6 to FIG. 8, the through grooves 322A and 322B have a sipe portion 3221 and a shallow bottom portion 3222.

The sipe portion 3221 is a cut formed on the tread surface, and has a maximum width W21 (see Figures 4 and 8) of 0.5 mm to 1.5 mm and a maximum depth H21 (see Figure 6) of 2.0 mm or more and less than the maximum groove depth Hg of the circumferential main groove 21, so that it is closed when the tire comes into contact with the ground. As shown in Figure 6, the maximum depth H21 of the sipe portion 3221 is shallower than the maximum groove depth Hg of the circumferential main groove 21. In Figure 7, the maximum depth H21 of the sipe portion 3221 of the through-hole fine grooves 322A and 322B has a relationship of -5.0 mm ≦ H21 - H11 ≦ 5.0 mm with respect to the maximum depth H11 of the sipe portion 3211 of the chamfered sipes 321A and 321B. In addition, it is preferable that the maximum depth H21 of the sipe portion 3221 of the fine through grooves 322A and 322B has a relationship of 0.10≦(H21/H11)≦10.0 with respect to the maximum depth H11 of the sipe portion 3211 of the chamfered sipes 321A and 321B. The above lower limit ensures the suppression of the crushing of the chamfered portion 3212 of the chamfered sipes 321A and 321B by the fine through grooves 322A and 322B, and the above upper limit suppresses the decrease in rigidity of the center land portion 32 caused by the maximum depth H21 of the fine through grooves 322A and 322B becoming excessive.

In the configurations of Figures 4 and 8, the sipe portion 3221 does not have a chamfered portion at the opening to the tread surface. In this configuration, the wall surface area of the sipe portion 3221 that meshes when the tire is in contact with the ground is large, so the rigidity of the center land portion 32 when the tire is in contact with the ground is properly ensured. On the other hand, the sipe portion 3221 may have a minute edge processing portion with a maximum width and maximum depth of less than 1.0 mm at the opening to the tread surface (not shown). Even with this configuration, the meshing of the sipe portion 3221 when the tire is in contact with the ground is properly ensured.

As shown in Figures 4 and 8, the sipe portions 3221 of the through grooves 322A and 322B are arranged opposite the chamfered sipes 321A and 321B. The sipe portions 3221 of the through grooves 322A and 322B and the sipe portions 3211 of the chamfered sipes 321A and 321B extend approximately parallel to each other and open into the edge portions of the center land portion 32.

As shown in Figures 4 and 8, the extension distance D21 of the sipe portion 3221 of the through grooves 322A and 322B in the tire width direction is in the range of 0.60 ≦ D21/D11 ≦ 1.50 relative to the extension distance D11 of the chamfered sipes 321A and 321B, and preferably in the range of 0.80 ≦ D21/D11 ≦ 1.20.

The shallow portion 3222 has a maximum width W22 (see FIG. 4 and FIG. 8) of 0.5 mm or more and 1.5 mm or less, and a maximum depth H22 (see FIG. 6) of 0.2 mm or more and less than 2.0 mm. As shown in FIG. 6, the maximum depth H22 of the shallow portion 3222 is set shallower than the maximum groove depth Hg of the circumferential main groove 21 and the maximum depth H21 of the sipe portion 3221, and specifically, it is preferable that the maximum width W22 of the shallow portion 3222 is in the range of 0.80 ≦ W22 / W21 ≦ 1.50 with respect to the maximum width W21 of the sipe portion 3221. For example, in the configurations of Figures 4 and 8, the maximum width W22 of the shallow portion 3222 is wider than the maximum width W21 of the sipe portion 3221, and has a relationship of 1.10 ≦ W22 / W21 ≦ 1.50, thereby enhancing the drainage effect of the shallow portion 3222. However, this is not limited to this, and the maximum width W22 of the shallow portion 3222 may be equal to or less than the maximum width W21 of the sipe portion 3221 (not shown).

The depth of the shallow bottom portion 3222 is measured as the distance from the tread surface to the maximum depth position of the shallow bottom portion 3222 when the tire is mounted on a specified rim, inflated to the specified internal pressure, and in an unloaded state.

As shown in Figures 4 and 8, the thin through grooves 322A and 322B have a V-shaped apex T1 at the shallow bottom portion 3222, and therefore the thin through grooves 322A and 322B are bent at the shallow bottom portion 3222.

For example, in the configurations of Figures 4 and 8, the through-slits 322A and 322B are formed by connecting the linear sipe portion 3221 and the V-shaped shallow bottom portion 3222, and the sipe portion 3221 and the shallow bottom portion 3222 are open to the left and right edge portions of the center land portion 32. In addition, the through-slits 322A and 322B have a V-shape formed by connecting the linear long and short sides, the sipe portion 3221 forms a part of the long side of the V-shape, and the shallow bottom portion 3222 forms the bent portion and short side of the V-shape. In addition, for example, the long side of the V-shape may have a gentle arc shape or an S-shape (not shown). In addition, in the configurations of Figures 4 and 8, the sipe portion 3221 extends from the end of the shallow bottom portion 3222 as shown in Figure 6. However, this is not limited to the above, and the sipe portion 3221 may extend from the groove bottom of the shallow bottom portion 3222, so that the sipe portion 3221 and the shallow bottom portion 3222 overlap each other in the tire width direction (not shown).

In the configuration of FIG. 4, as described above, the through-thin grooves 322A and 322B have a structure formed by connecting the sipe portion 3221 and the shallow bottom portion 3222. In addition, since the sipe portion 3221 has the above-mentioned predetermined maximum width W21, maximum depth H21, and extension distance D21 (see FIG. 4, FIG. 6, and FIG. 8), the through-thin grooves 322A and 322B properly suppress the crushing of the chamfered portion 3212 of the chamfered sipes 321A and 321B. In particular, since the sipe portion 3221 is a sipe that closes when the tire touches the ground, the rigidity of the center land portion 32 is secured compared to a configuration having a groove that opens when the tire touches the ground. In addition, since the shallow bottom portion 3222 extends the sipe portion 3221 and opens to the edge portion of the center land portion 32, the drainage action of the through-thin grooves 322A and 322B is properly secured.

However, this is not limited to the above, and the sipe portion 3221 of the through-groove 322A, 322B may penetrate the center land portion 32 (not shown). For example, in FIG. 4 and FIG. 8, the sipe portion 3221 may extend along the groove bottom of the shallow bottom portion 3222 and penetrate the center land portion 32 (not shown). In this case, the shallow bottom portion 3222 may be configured by raising the bottom of the sipe portion 3221 (not shown). The shallow bottom portion 3222 may be omitted, and the sipe portion 3221 may penetrate the center land portion 32 by itself (not shown). In addition, the through-groove 322A, 322B may not be closed when the tire is in contact with the ground, provided that it has the maximum width W21 and maximum depth H21 described above.

In addition, in the configuration of FIG. 3, the center land portion 32 does not have a lug groove with a maximum width exceeding 1.5 mm, and is not divided in the tire circumferential direction by such lug grooves. In addition, the chamfered sipes 321A, 321B have a semi-closed structure that does not penetrate the center land portion 32, and the through-groove 322A, 322B has a sipe portion 3221 that closes when the tire is in contact with the ground, so that the center land portion 32 is a rib with a contact surface that is continuous in the tire circumferential direction. This ensures the rigidity of the center region of the tread portion, and ensures the steering stability performance of the tire.

3, the left and right center land portions 32, 33 have the same structure. Specifically, the chamfered sipes 321A; 321B of one center land portion 32 and the chamfered sipes 321A; 321B of the other center land portion 33 are inclined in the same direction with respect to the tire circumferential direction. In each of the left and right center land portions 32, 33, the first chamfered sipe 321A of the first groove unit UA, i.e., the first chamfered sipe 321A arranged on the convex side of the first V-shaped through narrow groove 322A, opens to the edge portion on the outer side of the center land portions 32, 33 in the vehicle width direction. In addition, the groove units UA, UB of the left and right center land portions 32, 33 are arranged with a pitch offset in the tire circumferential direction, so that the chamfered sipes 321A, 321B of one center land portion 32 are arranged on an extension line (not shown) of the chamfered sipes 321A, 321B of the other center land portion 33. In this way, the left and right center land portions 32, 33 have an asymmetric structure.

However, this is not limiting, and the left and right center land portions 32, 33 may have a tread pattern that is line-symmetrical about the tire equatorial plane CL, a point-symmetrical tread pattern with a center point on the tire equatorial plane CL, or a tread pattern that has directionality in the tire rotation direction (not shown).

[Shoulder land area]
2, the shoulder land portions 31, 34 include a plurality of lug grooves 311, 341. In the configuration in Fig. 2, the shoulder land portions 31, 34 have a point-symmetric structure in the tire contact patch, so here, the configuration of the shoulder land portion 31 on the outer side in the vehicle width direction will be described, and a description of the shoulder land portion 34 on the inner side in the vehicle width direction will be omitted.

The lug grooves 311 are lateral grooves that extend in the tire width direction and have a maximum groove width of 2.0 mm or more and a maximum groove depth of 3.0 mm or more, so that they open and function as grooves when the tire comes into contact with the ground. In addition, the inclination angle of the lug grooves 311 with respect to the tire circumferential direction (dimension symbols omitted in the figure) is in the range of 80 degrees to 100 degrees, and is larger than the inclination angle θ1 of the chamfered sipes 321A and 321B in the center land portion. This optimizes the stiffness distribution across the entire tread surface.

The lug grooves 311 have a semi-closed structure, one end of which opens to the tire ground edge T, and the other end of which terminates within the ground contact surface of the shoulder land portion 31. A plurality of lug grooves 311 are arranged at a predetermined interval in the tire circumferential direction. The pitch length P1 of the lug grooves 311 of the shoulder land portion 31 has a relationship of 2.0≦P1/P2≦6.0 with respect to the pitch length P2 of the first chamfered sipe 321A of the center land portion 32 (i.e., the chamfered sipe 321A opening toward the shoulder main groove 21), and preferably has a relationship of 3.5≦P1/P2≦4.5. In the configuration of FIG. 2, the total number of lug grooves of the shoulder land portion 31 is set to be twice the total number of all the chamfered sipes 321A, 321B of the center land portion 32.

The shoulder land portion 31 also has multiple sipes (dimension symbols omitted in the figure). Specifically, the shoulder land portion 31 has a semi-closed structure and has multiple first sipes arranged between adjacent lug grooves 311, and multiple second sipes that extend from the end of the lug groove 311 in the tire width direction and open into the shoulder main groove 21. These sipes also extend approximately parallel to the lug groove 311.

[effect]
As described above, the tire 1 includes two or more circumferential main grooves 21-23 extending in the tire circumferential direction, a pair of shoulder land portions 31, 34 and one or more rows of center land portions 32, 33 partitioned by the circumferential main grooves 21-23 (see FIG. 2). The center land portions 32, 33 include a plurality of chamfered sipes 321A, 321B that open at one end to the edge portion of the center land portion 32, 33 and terminate at the other end within the center land portion 32, 33, and a plurality of thin through grooves 322A, 322B that penetrate the center land portions 32, 33 in the tire width direction (see FIG. 3). The thin through grooves 322A, 322B have a V-shape with the apex facing the tire circumferential direction, and are arranged so that one side of the V-shape faces the chamfered sipes 321A, 321B. In addition, the inclination angle θ1 (see FIG. 4) of the sipe portion 3211 of the chamfered sipes 321A, 321B with respect to the tire circumferential direction and the inclination angle θ2 of the one side of the V-shape of the thin through-grooves 322A, 322B have a relationship of −10 degrees≦θ1−θ2≦10 degrees.

In this configuration, (1) the fine through grooves 322A, 322B are arranged opposite the chamfered sipes 321A, 321B, so that the fine through grooves 322A, 322B are actively closed when the tire touches the ground, dispersing the ground pressure to the chamfered sipes 321A, 321B. As a result, compared to a configuration with only chamfered sipes (not shown), crushing of the chamfered portions 3212 of the chamfered sipes 321A, 321B is suppressed, and the drainage function of the chamfered portions 3212 is ensured. This ensures the wet performance of the tire. Furthermore, (2) one side of the V-shaped through-groove 322A, 322B (particularly the sipe portion 3221 in FIG. 4 and FIG. 8) is arranged approximately parallel (-10 [deg] ≦ θ1-θ2 ≦ 10 [deg]) to the sipe portion 3211 of the chamfered sipe 321A, 321B, so that the crushing of the chamfered portion 3212 of the chamfered sipe 321A, 321B is effectively suppressed compared to a configuration in which the two are not parallel (not shown). This effectively improves the wet performance of the tire. Also, (3) since the chamfered sipe 321A, 321B has a semi-closed structure that terminates within the center land portion 32, 33, the rigidity of the center land portion 32, 33 is ensured, and the steering stability performance of the tire on a dry road surface is improved compared to a configuration (not shown) having a chamfered sipe of an open structure that penetrates the land portion. In addition, (4) since the thin through grooves 322A, 322B have a V-shape, the rigidity of the center land portions 32, 33 is ensured compared to a configuration with straight-line thin through grooves (not shown). This suppresses deformation of the center land portions 32, 33 when the tire touches the ground, improving the steering stability of the tire on dry roads. The above (1) to (4) have the advantage of achieving both wet performance and steering stability of the tire on dry roads.

In addition, in this tire 1, the inclination angle θ1 (see FIG. 4 and FIG. 8) of the chamfered sipes 321A, 321B with respect to the tire circumferential direction is in the range of 30 [deg]≦θ1≦60 [deg]. The above lower limit has the advantage of properly ensuring the drainage action of the chamfered sipes 321A, 321B. In addition, the above upper limit has the advantage of efficiently ensuring the extension length of the chamfered sipes 321A, 321B compared to a configuration (not shown) in which the chamfered sipes are arranged approximately perpendicular to the tire circumferential direction.

In addition, in this tire 1, the extension distance D11 of the sipe portion 3211 of the chamfered sipes 321A, 321B in the tire width direction has a relationship of 0.40≦D11/Wb≦0.90 with respect to the maximum ground contact width Wb of the center land portion 32 (see Figures 4 and 8). The above lower limit has the advantage of properly ensuring the extension distance D11 of the chamfered sipes 321A, 321B, and properly ensuring the drainage function of the chamfered sipes 321A, 321B. The above upper limit also has the advantage of suppressing a decrease in the rigidity of the center land portion 32 caused by the extension distance D11 being excessive.

In addition, in this tire 1, the chamfered sipes 321A, 321B have chamfered portions 3212 only on the edge portions on the opposing thin through grooves 322A, 322B side of the left and right edges of the sipe portion 3211 (see Figures 4 and 8). In this configuration, the chamfered sipes 321A, 321B have a one-sided chamfered structure, and the chamfered portions 3212 are arranged between the sipe portion 3211 and the nearby thin through grooves 322A, 322B, that is, in a narrow area of the tread surface of the center land portion 32 partitioned by the adjacent chamfered sipes 321A, 321B and thin through grooves 322A, 322B, so that a wide contact area of the tread surface of the center land portion 32 is secured, which has the advantage of improving the steering stability performance of the tire on dry road surfaces.

In addition, in this tire 1, the maximum width W1 of the chamfered sipes 321A, 321B and the maximum width W11 of the sipe portion 3211 of the chamfered sipes 321A, 321B satisfy the conditions of 2.00≦W1/W11≦6.00 and 0.5 mm≦W11≦1.5 mm (see FIG. 4 and FIG. 8). This has the advantage of ensuring the proper function of the chamfered sipes 321A, 321B.

In addition, in this tire 1, the distance Da from one side of the V-shape of the through-thin grooves 322A, 322B to the sipe portion 3211 of the chamfered sipes 321A, 321B is in the range of 0.20≦Da/W11≦30 with respect to the maximum width W11 of the sipe portion 3211 of the chamfered sipes 321A, 321B (see FIG. 4 and FIG. 8). The lower limit ensures the distance Da from the through-thin grooves 322A, 322B to the sipe portion 3211, suppressing uneven wear in the area between the chamfered sipes 321A, 321B and the through-thin grooves 322A, 322B. The upper limit also has the advantage of properly ensuring the suppression effect of the through-thin grooves 322A, 322B in the crushing of the chamfered portion 3212 of the chamfered sipes 321A, 321B.

In addition, in this tire 1, the thin through grooves 322A, 322B have a maximum width W2 (see Figures 4 and 8) of 0.5 mm or more and 1.5 mm or less, and a maximum depth H2 (see Figure 6) of 2.0 mm or more and less than the maximum groove depth Hg of the circumferential main groove 21. This has the advantage of ensuring the proper function of the thin through grooves 322A, 322B.

In addition, in this tire 1, a single through-groove 322A; 322B is disposed between a pair of chamfered sipes 321A, 321B adjacent in the tire circumferential direction (see FIG. 3). In addition, of the pair of chamfered sipes 321A, 321B, a close chamfered sipe 321A; 321B disposed near the through-groove 322A; 322B and a remote chamfered sipe 321B; 321A disposed far from the through-groove 322A; 322B are defined. In this case, the maximum value Db_max of the distance Db from the center line of the sipe portion 3211 of the remote chamfered sipe 321B; 321A to the center line of the through-groove 322A, 322B is in the range of 1.50≦Db_max/Da_max≦12.0 relative to the maximum value Da_max of the distance Da from the center line of the sipe portion 3211 of the adjacent chamfered sipe 321A; 321B to the center line of the through-groove 322A, 322B. In this configuration, the through grooves 322A; 322B are biased between a pair of adjacent chamfered sipes 321A, 321B, which effectively prevents the chamfered portion 3212 of the adjacent chamfered sipes 321A; 321B from being crushed, improving the wet performance of the tire, and at the same time, the contact area from the through grooves 322A; 322B to the remote chamfered sipes 321B; 321A is secured, improving the dry steering stability of the tire.

In addition, in this tire 1, the V-shaped apexes T1 of the through grooves 322A and 322B are offset in the tire width direction from the center line of the center land portion 32 (see Figures 4 and 8). The open ends of the chamfered sipes 321A and 321B are arranged in one region bounded by the center line of the center land portion 32, and the V-shaped apexes T1 of the through grooves 322A and 322B are arranged in the other region. The distance Dt from the center line of the center land portion 32 to the V-shaped apexes T1 of the through grooves 322A and 322B is in the range of 0.10≦Dt/Wb≦0.40 with respect to the maximum ground contact width Wb of the center land portion 32. In this configuration, the apex T1 of the V-shape of the through grooves 322A, 322B is located in the region opposite the body of the chamfered sipes 321A, 321B in the tire width direction, so the extension length of the one side of the V-shape facing the chamfered sipes 321A, 321B can be extended. This has the advantage of effectively suppressing the crushing of the chamfered portions 3212 of the chamfered sipes 321A, 321B.

In addition, in this tire 1, the thin through grooves 322A, 322B are formed by connecting the sipe portion 3221 that is closed when the tire is in contact with the ground and the shallow bottom portion 3222 that is shallower than the sipe portion 3221, and the sipe portion 3221 is located on one side of the V shape (see Figures 4 and 8). This has the advantage that the sipe portion 3221 of the thin through grooves 322A, 322B is disposed opposite the sipe portion 3211 of the chamfered sipes 321A, 321B, and the crushing of the chamfered portion 3212 of the chamfered sipes 321A, 321B can be effectively suppressed.

The tire 1 also has first and second groove units UA and UB consisting of chamfered sipes 321A and 321B and through-grooves 322A and 322B (see FIG. 3). The chamfered sipes 321A of the first groove unit UA open to one edge of the center land portion 32, and the chamfered sipes 321B of the second groove unit UB open to the other edge of the center land portion 32. The first groove units UA and the second groove units UB are arranged alternately in the tire circumferential direction. In this configuration, the chamfered sipes 321A and 321B having a semi-closed structure are arranged in a staggered pattern in the tire circumferential direction and open alternately to the left and right edges of the center land portion 32. This has the advantage of making the rigidity of the edge portion of the center land portion 32 uniform.

In addition, in this tire 1, the narrow through grooves 322A, 322B adjacent to each other in the tire circumferential direction are arranged so that their V-shapes face in opposite directions (see FIG. 3). This has the advantage that the rigidity of the center land portion 32 is made uniform, and the external force acting on the center land portion 32 when the tire is in contact with the ground is dispersed.

[Applies to]
In this embodiment, as described above, a pneumatic tire has been described as an example of a tire. However, the present invention is not limited to this, and the configuration described in this embodiment can be arbitrarily applied to other tires within the scope of what is obvious to a person skilled in the art. Examples of other tires include airless tires and solid tires.

Figures 9 and 10 are charts showing the results of performance tests on tires according to an embodiment of the present invention.

In this performance test, several types of test tires were evaluated for (1) wet braking performance and (2) dry steering stability performance. In addition, test tires with a tire size of 195/60R17 were mounted on JATMA-specified rims, and the test tires were subjected to the JATMA-specified internal pressure and load. In addition, the test tires were mounted on all wheels of a passenger car, which was the test vehicle.

(1) For the evaluation of wet braking performance, the test vehicle runs on an asphalt road that has been watered to a depth of 1 mm, and the braking distance from an initial speed of 40 km/h is measured. Then, based on the measurement results, an index evaluation is performed with the comparative example set as the standard (100). The higher the evaluation value, the more preferable it is.

(2) In the evaluation of dry steering stability performance, the test vehicle is driven on a test course, and a professional test driver performs a feeling evaluation of lane change performance, cornering performance, etc. This evaluation is performed using an index evaluation with the comparative example as the standard (100), and the higher the value, the more preferable it is.

The test tire of the embodiment has the configuration of Figures 1 and 2, and each of the two rows of center land portions 32, 33 has a plurality of groove units UA; UB consisting of chamfered sipes 321A; 321B and through-groove thin grooves 322A; 322B. The chamfered sipes 321A, 321B have a straight shape, and the through-groove thin grooves 322A, 322B have a V-shape with the top facing the tire circumferential direction. The shoulder main grooves 21, 23 have a maximum groove width of 8.9 [mm] and a maximum groove depth Hg of 7.1 [mm] (see Figure 5), and the center main groove 22 has a maximum groove width of 8.8 [mm] and a maximum groove depth of 9.6 [mm]. The tire ground contact width TW is 146 [mm], and the ground contact width Wb of the center land portions 32, 33 is 23 [mm]. In Example 1, the fine through grooves 322A and 322B are through sipes (not shown) that penetrate the center land portion 32 to a certain depth, and do not have shallow bottom portions 3222. On the other hand, in Example 9, the fine through grooves 322A and 322B are composed of the sipe portion 3221 and shallow bottom portion 3222 shown in Figures 4 to 8. In addition, the ratio P2'/P2 in Figure 4 is 0.50, and the average value of the distance Da+Db is 35 mm.

The comparative test tire has the same configuration as in Example 1, with the chamfered sipes 321A, 321B and through-grooves 322A, 322B having a linear shape that extends parallel to the tire width direction (not shown).

As the test results show, the test tires of the embodiment exhibit both wet braking performance and dry steering stability.

1 Tire; 11 Bead core; 12 Bead filler; 13 Carcass layer; 14 Belt layer; 141, 142 Cross belt; 143 Belt cover; 15 Tread rubber; 16 Sidewall rubber; 17 Rim cushion rubber; 21, 22 Circumferential main groove; 31, 34 Shoulder land portion; 311 Lug groove; 32, 33 Center land portion; 321A First chamfered sipe; 321B Second chamfered sipe; 322A First through narrow groove; 322B Second through narrow groove; 3211 Siped portion; 3212 Chamfered portion; 3221 Siped portion; 3222 Shallow bottom portion; UA First groove unit; UB Second groove unit

Claims (9)

A tire having two or more circumferential main grooves extending in a tire circumferential direction, and a pair of shoulder land portions and one or more rows of center land portions defined by the circumferential main grooves,
The center land portion includes a plurality of chamfered sipes that open at one end to an edge portion of the center land portion and terminate within the center land portion at the other end, and a plurality of through-grooves that penetrate the center land portion in the tire width direction,
The thin through groove has a V-shape with an apex facing in the tire circumferential direction and is disposed so that one side of the V-shape faces the chamfered sipe,
an inclination angle θ1 of the sipe portion of the chamfered sipe with respect to the tire circumferential direction and an inclination angle θ2 of the one side of the V-shape of the through-groove have a relationship of −10 [deg]≦θ1−θ2≦10 [deg];
The inclination angle θ1 of the chamfered sipe with respect to the tire circumferential direction is in the range of 30 [deg]≦θ1≦60 [deg],
A single through-groove is disposed between a pair of the chamfered sipes adjacent to each other in the tire circumferential direction,
Among the pair of chamfered sipes, a close chamfered sipe arranged at a position close to the through-groove and a remote chamfered sipe arranged at a position far from the through-groove are defined, and
a maximum value Db_max of a distance Db from a center line of a sipe portion of the remote-chamfered sipe to a center line of the fine through-groove, relative to a maximum value Da_max of a distance Da from the center line of a sipe portion of the adjacent-chamfered sipe to the center line of the fine through-groove, in a range of 1.50≦Db_max/Da_max≦12.0. The tire according to claim 1 , wherein the chamfered sipe has a chamfered portion only on an edge portion on the side of the thin through-groove out of left and right edge portions of the sipe portion. The apex of the V-shape of the through-groove is offset in the tire width direction with respect to the center line of the center land portion, so that the open end of the chamfered sipe is located in one region bounded by the center line of the center land portion, and the apex of the V-shape of the through-groove is located in the other region, and
3. The tire according to claim 1, wherein a distance Dt from a center line of the central land portion to the apex of the V-shape of the through-groove is in a range of 0.10≦Dt/Wb≦0.40 with respect to a maximum ground contact width Wb of the central land portion. The tire according to any one of claims 1 to 3, wherein the through-groove is formed by connecting a sipe portion that is closed when the tire is in contact with the ground and a shallow bottom portion that is shallower than the sipe portion, and the sipe portion is provided on one side of the V -shape. a first groove unit and a second groove unit each including the chamfered sipe and the through groove;
The chamfered sipe of the first groove unit opens to one edge portion of the center land portion,
The chamfered sipe of the second groove unit opens to the other edge portion of the center land portion, and
The tire according to any one of claims 1 to 4 , wherein the first groove units and the second groove units are arranged alternately in the tire circumferential direction. The tire according to any one of claims 1 to 5 , wherein the narrow through-grooves adjacent to each other in the tire circumferential direction are arranged so that the V-shapes are oriented in opposite directions to each other. A tire having two or more circumferential main grooves extending in a tire circumferential direction, and a pair of shoulder land portions and one or more rows of center land portions defined by the circumferential main grooves,
The center land portion includes a plurality of chamfered sipes that open at one end to an edge portion of the center land portion and terminate within the center land portion at the other end, and a plurality of through-grooves that penetrate the center land portion in the tire width direction,
The thin through groove has a V-shape with an apex facing in the tire circumferential direction and is disposed so that one side of the V-shape faces the chamfered sipe,
an inclination angle θ1 of the sipe portion of the chamfered sipe with respect to the tire circumferential direction and an inclination angle θ2 of the one side of the V-shape of the through-groove have a relationship of −10 [deg]≦θ1−θ2≦10 [deg];
The inclination angle θ1 of the chamfered sipe with respect to the tire circumferential direction is in the range of 30 [deg]≦θ1≦60 [deg], and
A tire characterized in that the apex of the V-shape of the through-groove is positioned offset in the tire width direction with respect to the center line of the central land portion, such that the open end of the chamfered sipe is positioned in one region bounded by the center line of the central land portion, and the apex of the V-shape of the through-groove is positioned in the other region. A tire having two or more circumferential main grooves extending in a tire circumferential direction, and a pair of shoulder land portions and one or more rows of center land portions defined by the circumferential main grooves,
The center land portion includes a plurality of chamfered sipes that open at one end to an edge portion of the center land portion and terminate within the center land portion at the other end, and a plurality of through-grooves that penetrate the center land portion in the tire width direction,
The thin through groove has a V-shape with an apex facing in the tire circumferential direction and is disposed so that one side of the V-shape faces the chamfered sipe,
an inclination angle θ1 of the sipe portion of the chamfered sipe with respect to the tire circumferential direction and an inclination angle θ2 of the one side of the V-shape of the through-groove have a relationship of −10 [deg]≦θ1−θ2≦10 [deg];
The inclination angle θ1 of the chamfered sipe with respect to the tire circumferential direction is in the range of 30 [deg]≦θ1≦60 [deg],
A tire comprising first and second groove units each consisting of the chamfered sipe and the through-groove, the chamfered sipe of the first groove unit opening to one edge portion of the center land portion and the chamfered sipe of the second groove unit opening to the other edge portion of the center land portion, and the first groove units and the second groove units are arranged alternately in the tire circumferential direction. A tire having two or more circumferential main grooves extending in a tire circumferential direction, and a pair of shoulder land portions and one or more rows of center land portions defined by the circumferential main grooves,
The center land portion includes a plurality of chamfered sipes that open at one end to an edge portion of the center land portion and terminate within the center land portion at the other end, and a plurality of through-grooves that penetrate the center land portion in the tire width direction,
The thin through groove has a V-shape with an apex facing in the tire circumferential direction and is disposed so that one side of the V-shape faces the chamfered sipe,
an inclination angle θ1 of the sipe portion of the chamfered sipe with respect to the tire circumferential direction and an inclination angle θ2 of the one side of the V-shape of the through-groove have a relationship of −10 [deg]≦θ1−θ2≦10 [deg];
The inclination angle θ1 of the chamfered sipe with respect to the tire circumferential direction is in the range of 30 [deg]≦θ1≦60 [deg], and
The tire is characterized in that the narrow through-grooves adjacent to each other in the tire circumferential direction are arranged so that the V-shapes are oriented in opposite directions to each other.

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