Patent ID: 12187077

DETAILED DESCRIPTION

Embodiments of the technology will be described in detail below with reference to the drawings. Note that embodiments of the technology are not limited to the embodiments. Additionally, constituents of the embodiments include constituents that are substitutable and are obviously substitutes while maintaining consistency with the embodiments of the technology. Additionally, a plurality of modified examples described in the embodiments can be combined in a discretionary manner within the scope apparent to one skilled in the art.

Tire

FIG.1is a cross-sectional view in a tire meridian direction illustrating a tire according to an embodiment of the technology. The same drawing illustrates a cross-sectional view of a half region in a tire radial direction. In this embodiment, a racing pneumatic radial tire used both for public road running and for circuit running will be described as an example of the tire.

In the same drawing, a cross section in the tire meridian direction is defined as a cross section of the tire taken along a plane that includes a tire rotation axis (not illustrated). Further, a tire equatorial plane CL is defined as a plane perpendicular to the tire rotation axis through a midpoint between measurement points in a tire cross-sectional width defined by JATMA (the Japan Automobile Tyre Manufacturers Association Inc.). Additionally, a tire width direction is defined as a direction parallel to the tire rotation axis, and the tire radial direction is defined as a direction perpendicular to the tire rotation axis.

Furthermore, an inner side in a vehicle width direction and an outer side in the vehicle width direction are defined with respect to the vehicle width direction in a case where the tire is mounted on a vehicle. Additionally, left and right regions demarcated by the tire equatorial plane are defined as an outer region in the vehicle width direction and an inner region in the vehicle width direction. Furthermore, the tire includes a mounting direction indicator (not illustrated) that indicates the tire mounting direction with respect to a vehicle. The mounting direction indicator, for example, is composed of a mark or recesses/protrusions on a sidewall portion of the tire. For example, Economic Commission for Europe Regulation 30 (ECE R30) stipulates that the vehicle mounting direction indicator be provided on the sidewall portion on the outer side in the vehicle width direction in a case where the tire is mounted on a vehicle.

A tire1includes an annular structure with the tire rotation axis serving as the center, and includes a pair of bead cores11,11, a pair of bead fillers12,12, a carcass layer13, a belt layer14, a tread rubber15, a pair of sidewall rubbers16,16, a pair of rim cushion rubbers17,17, and an innerliner18(seeFIG.1).

The pair of bead cores11,11each include one or more of bead wires made of steel and made by being wound annularly multiple times, and the pair of bead cores11,11are embedded in bead portions and constitute cores of the bead portions on the left and right. The pair of bead fillers12,12are respectively disposed on an outer circumference of the pair of bead cores11,11in the tire radial direction and reinforce the bead portions.

The carcass layer13includes a single layer structure made of one carcass ply, or a multilayer structure made of a plurality of carcass plies being layered, and the carcass layer13extends in a toroidal shape between the bead cores11,11on the left and right, and constitutes the backbone of the tire. Additionally, both end portions of the carcass layer13are wound and turned back toward an outer side in the tire width direction to wrap the bead cores11and the bead fillers12, and are fixed. Moreover, the carcass ply of the carcass layer13is made by covering a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon, or the like) with a coating rubber and performing a rolling process on the carcass cords, and has a cord angle (defined as an inclination angle in a longitudinal direction of the carcass cords with respect to a tire circumferential direction) of 80 degrees or more and 100 degrees or less.

Note that in the configuration inFIG.1, the carcass layer13includes a multilayer structure made by layering two carcass plies131,132. However, no such limitation is intended, and the carcass layer13may be constituted by layering three or more carcass plies or may include a single layer structure made of one carcass ply (not illustrated).

The belt layer14is a multilayer structure including a plurality of belt plies141to143and is disposed around the periphery of the carcass layer13. The belt plies141to143include a pair of cross belts141,142and a pair of belt covers143,143.

The pair of cross belts141,142are made by covering a plurality of belt cords made of steel or an organic fiber material with a coating rubber and performing a rolling process on the belt cords, and each have a cord angle with an absolute value of 15 degrees or more and 55 degrees or less. Further, the pair of cross belts141,142have cord angles (defined as inclination angles in a longitudinal direction of the belt cords with respect to the tire circumferential direction) of opposite signs relative to each other and are layered such that the longitudinal directions of the belt cords intersect each other (so-called crossply structure). Furthermore, the pair of cross belts141,142are disposed layered on an outer side in the tire radial direction of the carcass layer13.

The belt cover143is made by coating belt cover cords made from steel or an organic fiber material with a coating rubber and has a cord angle, as an absolute value, of 0° or more and 10° or less. Additionally, the belt cover143is, for example, a strip material formed by coating one or a plurality of belt cover cords with a coating rubber, where the strip material is formed by winding the strip material spirally on the outer circumferential surfaces of the cross belts141and142multiple times in the tire circumferential direction. Additionally, in the configuration inFIG.1, the belt covers143,143are disposed covering lateral edges of the cross belts141,142from the outer side in the tire radial direction. However, no such limitation is intended, and the belt cover143may be disposed in such a manner as to completely cover the cross belts141,142(not illustrated).

The tread rubber15is disposed in the outer circumferences in the tire radial direction of the carcass layer13and the belt layer14and constitutes a tread portion of the tire. The pair of sidewall rubbers16,16are disposed on an outer side in the tire width direction of the carcass layer13and constitute sidewall portions on the left and right, respectively. The pair of rim cushion rubbers17,17extend from an inner side in the tire radial direction of the bead cores11,11on the left and right and turned back portions of the carcass layer13toward the outer side in the tire width direction, and constitute rim fitting surfaces of the bead portions. The innerliner18is an air permeation preventing layer disposed on the tire inner surface and covering the carcass layer13, and suppresses oxidation caused by exposure of the carcass layer13and also prevents leaking of the air in the tire.

Additionally, inFIG.1, a tire cross-sectional height SH has the relationship 0.20≤SH/SW≤0.70 and preferably has the relationship 0.30≤SH/SW≤0.60, with respect to a total tire width SW. In addition, a tire ground contact width TW has the relationship 0.90≤TW/SW≤0.98 and preferably has the relationship 0.94≤TW/SW≤0.96, with respect to the total tire width SW. Additionally, a belt width Wb of the cross belt141, which is wide, has the relationship 0.98≤Wb/TW≤1.10 and preferably has the relationship 1.00≤Wb/TW≤1.0.5, with respect to the tire ground contact width TW.

The tire cross-sectional height SH is a distance equal to half of a difference between a tire outer diameter and a rim diameter, and is measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.

The total tire width SW is measured as a linear distance (including all portions such as letters and patterns on the tire side surface) between the sidewalls when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.

The tire ground contact width TW is measured as a maximum linear distance in the tire axial direction of a contact surface of the tire and a flat plate when the tire is mounted on a specified rim, inflated to a specified internal pressure, placed perpendicular to the flat plate in a static state, and loaded with a load corresponding to a specified load.

A tire ground contact edge T is defined as a maximum width position in the tire axial direction of the contact surface between the tire and a flat plate when the tire is mounted on a specified rim, inflated to a specified internal pressure, placed perpendicular to the flat plate in a static state, and loaded with a load corresponding to a specified load.

The width of a belt ply is the distance in the direction of the tire rotation axis between the left and right end portions of each belt ply, measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.

“Specified rim” refers to an “applicable rim” defined by the Japan Automobile Tyre Manufacturers Association Inc. (JATMA), a “Design Rim” defined by the Tire and Rim Association, Inc. (TRA), or a “Measuring Rim” defined by the European Tyre and Rim Technical Organisation (ETRTO). Additionally, “specified internal pressure” refers to a “maximum air pressure” defined by JATMA, to the maximum value in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or to “INFLATION PRESSURES” defined by ETRTO. Additionally, “specified load” refers to a “maximum load capacity” defined by JATMA, the maximum value in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO. However, in the case of JATMA, for a tire for a passenger vehicle, the specified internal pressure is an air pressure of 180 kPa, and the specified load is 88% of the maximum load capacity.

Tread Surface

FIG.2is a plan view illustrating a tread surface of the tire1illustrated inFIG.1.FIG.3is an explanatory diagram illustrating a circumferential groove21(22) illustrated inFIG.2. In the drawings, “tire circumferential direction” refers to a direction around the tire rotation axis. Additionally, reference sign T denotes a tire ground contact edge, and dimension symbol TW denotes a tire ground contact width.

As illustrated inFIG.2, the tire1is provided with first and second circumferential grooves21,22in the tread surface. Additionally, as described below, the tire1includes no other circumferential grooves or dimples in the tread surface.

The circumferential grooves21,22need to extend intermittently or continuously in the tire circumferential direction. In the configuration illustrated inFIG.2, each of the first and second circumferential grooves21,22includes a plurality of groove portions211,221arranged discontinuously in a row in the tire circumferential direction and extend intermittently in the tire circumferential direction.

Specifically, the plurality of groove portions211constituting the first circumferential groove21are arranged discontinuously in a row in the tire circumferential direction along a predetermined imaginary line X1that is parallel with a tire equatorial plane CL. Additionally, the distance of the center of gravity of all of the groove portions211with respect to the imaginary line X1(dimension symbol omitted in the drawings) is in the range of less than 0.5% of the tire ground contact width TW. In other words, a group of groove portions211that satisfies the conditions for the distance described above with respect to the predetermined imaginary line X1constitutes one row of the first circumferential groove21. In addition, the imaginary line X1is defined as the groove center line of the first circumferential groove21.

Similarly, the plurality of groove portions221that constitute the second circumferential groove22are arranged discontinuously in a row in the tire circumferential direction along a predetermined imaginary line X2that is parallel with the tire equatorial plane CL. Additionally, the distance of the center of gravity of all of the groove portions221with respect to the imaginary line X2(dimension symbol omitted in the drawings) is in the range of less than 0.5% of the tire ground contact width TW. In other words, a group of groove portions221that satisfies the conditions for the distance described above with respect to the predetermined imaginary line X2constitutes one row of the second circumferential groove22. Furthermore, this imaginary line X2is defined as the groove center line of the second circumferential groove22.

The distance of the center of gravity of the groove portion211and the distance of the center of gravity of the groove portion221are measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.

Additionally, a maximum groove width W1of the first circumferential groove21and a maximum groove width W2of the second circumferential groove22have the relationships 0.020≤W1/TW≤0.080 and 0.020≤W2/TW≤0.080 with respect to the tire ground contact width TW. In addition, the maximum groove widths W1, W2of the first and second circumferential grooves21,22are in the range of 4.0 mm or more and 16 mm or less, and preferably in the range of 6.0 mm or more and 10 mm or less. Additionally, the maximum groove widths W1, W2of the first and second circumferential grooves21,22have the relationship 0.90≤W2/W1≤1.10, and preferably have the relationship 0.95≤W2/W1≤1.05.

The maximum groove widths W1, W2of the circumferential grooves21,22are each measured as a distance between opposite groove walls in a groove opening portion when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. In a case where the circumferential grooves21,22extend intermittently in the tire circumferential direction as illustrated inFIG.2, the maximum groove width is measured as the maximum value of the groove widths of all of the groove portions211,221constituting the single circumferential groove21,22.

Additionally, inFIG.3, the maximum groove depth H1of the first circumferential groove21and the maximum groove depth H2of the second circumferential groove22are in the range of 2.5 mm or more and 5.0 mm or less, and preferably in the range of 2.8 mm or more and 4.0 mm or less.

The maximum groove depths H21, H22of the circumferential grooves21,22are each measured as a distance from the tread contact surface to the groove bottom when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. Additionally, in a configuration in which a groove bottom includes partial recess/protrusion portions or a sipe, the groove depth is measured excluding the partial recess/protrusion portions or the sipe.

Additionally, inFIG.3, the maximum groove depths H1, H2of the first and second circumferential grooves21,22are in the range of 60% or more and 85% or less and preferably in the range of 63% or more and 70% or less with respect to the gauge Gr of the tread rubber15on the groove center line of the circumferential grooves21,22. Additionally, the gauge Gr of the tread rubber15is in the range of 30% or more and 60% or less and preferably in the range of 35% or more and 55% or less with respect to the total gauge Gt of the tread portion on the groove center lines of the circumferential grooves21,22.

The gauge Gr of the tread rubber15is measured as a distance from a tread profile to the outer circumferential surface of the cross belt142and does not include the gauge of the coating rubber (not illustrated) of the cross belt142.

The total gauge Gt of the tread portion is measured as a distance from the tread profile to the tire inner surface and does not include the gauge of the tread surface or partial recess/protrusion portions formed on the tire inner surface.

Additionally, inFIG.2, the groove area A1of the first circumferential groove21and the groove area A2(not illustrated) of the second circumferential groove22have the relationships 0.015≤A1/Sa≤0. 100 and 0.015≤A2/Sa≤0.100, and preferably have the relationships 0.015≤A1/Sa≤0.020 and 0.015≤A2/Sa≤0.020, with respect to an area Sa of the tire ground contact region.

The groove area is the opening area of a groove in the tread contact surface, and is measured at a contact surface between the tire and a flat plate when the tire is mounted on a specified rim, inflated to a specified internal pressure, placed vertically on the flat plate in a static state, and loaded with a load corresponding to a specified load. Additionally, in a case where the circumferential groove21,22extends intermittently in the tire circumferential direction as inFIG.2, the groove area A1, A2of the circumferential groove21,22is calculated as the sum of the opening areas of the plurality of groove portions211,221constituting the circumferential groove21,22.

The area Sa of the tire ground contact region is the area of the entire region of the tread contact surface defined by left and right tire ground contact edges T, and is defined as an area including both the groove and the land portion.

Additionally, in the configuration inFIG.2, each of the first and second circumferential grooves21,22includes a plurality of groove portions211,221arranged discontinuously in a row in the tire circumferential direction, as described above. Additionally, each of the opening areas of the groove portions211,221constituting the first and second circumferential grooves21,22is in the range of 200 mm2or more and 340 mm2or less, and preferably in the range of 240 mm2or more and 300 mm2or less.

Additionally, preferably the tire1has a tire ground contact region that does not include other grooves or recess portions each having an opening area of more than 40 mm2, preferably more than 20 mm2, that is, grooves or recess portions other than the circumferential grooves21,22. In other words, the regions other than the regions where the circumferential grooves21,22are disposed may be provided in the tire ground contact region with wear indicators (not illustrated) each including a recess portion or groove with an opening area smaller than that indicated in the above-described conditions, for example, a small hole. Additionally, the groove area ratio of the tire ground contact region is in the range of 3.0% or more and 5.0% or less, and preferably in the range of 3.2% or more and 3.8% or less.

For example, in the configuration inFIG.2, the tire ground contact region includes only the first and second circumferential grooves21,22, and a wear indicator (not illustrated) is formed in the groove bottoms of predetermined ones of the circumferential grooves21,22. Additionally, the regions other than the regions where the circumferential grooves21and22are disposed include a plane road contact surface with no grooves or sipes. Thus, in the configuration inFIG.2, the groove area across the tire ground contact region is equal to the sum of the groove area A1of the first circumferential groove21and the groove area A2of the second circumferential groove22. Additionally, the groove area ratio of the tire ground contact region is in the range 0.030≤(A1+A2)/Sa≤0.200.

The groove area ratio is defined as the ratio between the sum of the groove areas of the grooves disposed in a predetermined region and the area of the predetermined region.

Additionally, in the configuration inFIG.2, a pitch length P1of the groove portion211of the first circumferential groove21and a pitch length P2of the groove portion221of the second circumferential groove22have the relationships 0.030≤P1/TL≤0.060 and 0.030≤P2/TL≤0.060 with respect to a tire circumferential length TL (not illustrated).

The tire circumferential length TL is measured as the maximum circumferential length of the tread surface when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.

Additionally, inFIG.2, the maximum circumferential length L1of the groove portion211of the first circumferential groove21and the maximum circumferential length L2of the groove portions221of the second circumferential groove22have the relationships 0.30≤L1/P1≤0.60 and 0.30≤L2/P2≤0.60, and preferably have the relationships 0.45≤L1/P1≤0.55 and 0.45≤L2/P2≤0.55 with respect to the pitch length P1of the groove portion211of the first circumferential groove21and the pitch length P2of the groove portion221of the second circumferential groove22.

The maximum circumferential lengths L1, L2of the groove portions211,221of the circumferential grooves21,22are each measured as a circumferential distance in the groove opening portion when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.

Additionally, inFIG.2, the maximum circumferential length L1of the groove portion211of the first circumferential groove21and the maximum circumferential length L2of the groove portion221of the second circumferential groove22have the relationships 2.00≤L1/W1≤8.00 and 2.00≤L2/W2≤8.00, and preferably have the relationships 4.00≤L1/W1≤6.00 and 4.00≤L2/W2≤6.00 with respect to the maximum groove width W1of the first circumferential groove21and the maximum groove width W2of the second circumferential groove22.

Additionally, inFIG.2, the phase difference φ between the groove portion211of the first circumferential groove21and the groove portion221of the second circumferential groove22has the relationship 0.25≤φ/P1≤0.75 and preferably has the relationship 0.40≤φ/P1≤0.50 with respect to the pitch length P1of the groove portion211of the first circumferential groove21.

For example, in the configuration inFIG.2, the groove portions211,221have a rectangular shape or an elliptical shape that is elongated in the tire circumferential direction. Additionally, the groove portions211of the first circumferential groove21and the groove portions221of the second circumferential groove22are arranged in a staggered manner in the tire circumferential direction. Specifically, the pitch number of the groove portions211of the first circumferential groove21and the pitch number of the groove portions221of the second circumferential groove22are set to be identical, and the maximum circumferential length L1of the groove portion211of the first circumferential groove21and the maximum circumferential length L2of the groove portion221of the second circumferential groove22are set to be 50% of the pitch length P1of the groove portion211of the first circumferential groove21and the pitch length P2of the groove portion221of the second circumferential groove22. Additionally, the phase difference φ between the groove portion211of the first circumferential groove21and the groove portion221of the second circumferential groove22is set to be approximately 50% of the pitch length P1of the groove portion211of the first circumferential groove21.

Difference in Groove Volume Between Circumferential Grooves

In the tire1, as illustrated inFIG.2, the first circumferential groove21is disposed in an outer region in the vehicle width direction, whereas the second circumferential groove22is disposed in an inner region in the vehicle width direction, the outer region and the inner region being demarcated by the tire equatorial plane CL. Additionally, a distance D1from the tire equatorial plane CL to the groove center line X1of the first circumferential groove21is substantially equal to a distance D2from the second circumferential groove22to the groove center line X2. Accordingly, the first and second circumferential grooves21,22are disposed at a substantially identical position with respect to the tire equatorial plane CL. Additionally, the distance D1of the first circumferential groove21and the distance D2of the second circumferential groove22have the relationship 0.90≤D2/D1≤1.10, and preferably have the relationship 0.95≤D2/D1≤1.05.

Additionally, inFIG.2, the distances D1, D2from the tire equatorial plane CL to the groove center lines X1, X2of the first and second circumferential grooves21,22have the relationships 0.05≤D1/TW≤0.45 and 0.05≤D2/TW≤0.45, and preferably have the relationships 0.10≤D1/TW≤0.25 and 0.10≤D2/TW≤0.25 with respect to the tire ground contact width TW. Additionally, a distance Dg in the tire width direction between the groove center line X1of the first circumferential groove21and the groove center line X2of the second circumferential groove22has the relationship 0.10≤Dg/TW, and preferably has the relationship 0.20≤Dg/TW with respect to the tire ground contact width TW. The upper limit of the ratio Dg/TW is not particularly limited, but is restricted by other conditions.

The distance D1, the distance D2, and the distance Dg are measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.

Additionally, the groove volume V1of the first circumferential groove21and the groove volume V2of the second circumferential groove22have the relationship V1<V2. Thus, the first and second circumferential grooves21,22have different groove volumes V1, V2. Additionally, the groove volume V1of the first circumferential groove21and the groove volume V2of the second circumferential groove22have the relationship 1.11≤V2/V1≤2.00, and preferably have the relationship 1.20≤V2/V1≤1.80.

The groove volume is measured as the volume of a region surrounded by the tread contact surface and the groove wall surface. Additionally, in a case where the circumferential groove21,22extends intermittently in the tire circumferential direction as illustrated inFIG.2, the groove volume V1, V2of the circumferential groove21,22is calculated as the sum of the volumes of the plurality of groove portions211,221constituting the circumferential groove21,22.

In the configuration described above, since the groove volume V2of the second circumferential groove22on the inner side in the vehicle width direction is greater than the groove volume V1of the first circumferential groove21on the outer side in the vehicle width direction (V1<V2), the groove volume in the inner region in the vehicle width direction of the tread surface increases, which improves the tire wet performance, and the rigidity of the land portion in the outer region in the vehicle width direction increases, which improves the tire traction performance on dry road surfaces. Thus, the tire wet performance and the traction performance on dry road surfaces are improved in a compatible manner.

For example, in the configuration inFIG.2, the groove area A1of the first circumferential groove21and the groove area A2of the second circumferential groove22have a relationship such that A1<A2. Additionally, the groove area A1of the first circumferential groove21and the groove area A2of the second circumferential groove22have the relationship 1.11≤A2/A1≤2.00, and preferably have the relationship 1.20≤A2/A1≤1.80.

More specifically, the maximum groove width W1of the first circumferential groove21and the maximum groove width W2of the second circumferential groove22have the relationship W1<W2. Additionally, the maximum groove width W1of the first circumferential groove21and the maximum groove width W2of the second circumferential groove22have the relationship 1.11≤W2/W1, and preferably have the relationship 1.20≤W2/W1. The upper limit of the ratio W2/W1is not particularly limited, but is subject to restrictions by other conditions.

Additionally, inFIG.3, the maximum depth H1of the first circumferential groove21and the maximum depth H2of the second circumferential groove21are substantially equal and have the relationship 0.90≤H2/H1≤1.10, and preferably have the relationship 0.95≤H2/H1≤1.05.

Additionally, in the configuration inFIG.2, the pitch length P1of the groove portion211of the first circumferential groove21and the pitch length P2of the groove portion221of the second circumferential groove22have the relationship 0.90≤P1/P2≤1.10, and preferably have the relationship 0.95≤P1/P2≤1.05.

In addition, in the configuration inFIG.2, the maximum circumferential length L1of the groove portion211of the first circumferential groove21and the maximum circumferential length L2of the groove portion221of the second circumferential groove22have the relationship such that 0.90≤L2/L1≤1.10, and preferably have the relationship 0.95≤L2/L1≤1.05.

MODIFIED EXAMPLE 1

FIG.4andFIG.5are explanatory diagrams illustrating a modified example of the tire illustrated inFIG.2. In these drawings, constituents that are the identical to constituents illustrated inFIG.2have identical reference signs, and explanations thereof are omitted.

In the configuration inFIG.2, the maximum groove width of the first circumferential groove21and the maximum groove width of the second circumferential groove22have the relationship W1<W2, thus forming the relationship between the groove area A1of the first circumferential groove21and the groove area A2of the second circumferential groove22such that A1<A2, as described above.

In contrast, in the configuration inFIG.4, the pitch length P1of the groove portion211of the first circumferential groove21and the pitch length P2of the groove portion221of the second circumferential groove22have the relationship P2<P1, thus forming the relationship between the groove area A1of the first circumferential groove21and the groove area A2of the second circumferential groove22such that A1<A2. Specifically, the pitch length P1of the groove portion211of the first circumferential groove21and the pitch length P2of the groove portion221of the second circumferential groove22have the relationship 1.11≤P1/P2, and preferably have the relationship 1.20≤P1/P2. The upper limit of the ratio P1/P2is not particularly limited, but is restricted by other conditions.

Additionally, in the configuration inFIG.4, the maximum groove width W1of the first circumferential groove21and the maximum groove width W2of the second circumferential groove22are substantially equal and have the relationship 0.90≤W2/W1≤1.10, and preferably have the relationship 0.95≤W2/W1≤1.05.

Additionally, the maximum depth H1of the first circumferential groove21and the maximum depth H2of the second circumferential groove21(seeFIG.3) are substantially equal and have the relationship 0.90≤H2/H1≤1.10, and preferably have the relationship 0.95≤H2/H1≤1.05.

Additionally, inFIG.4, the maximum circumferential length L1of the groove portion211of the first circumferential groove21and the maximum circumferential length L2of the groove portion221of the second circumferential groove22have the relationship 0.90≤L2/L1≤1.10, and preferably have the relationship 0.95≤L2/L1≤1.05.

On the other hand, in the configuration inFIG.5, the maximum circumferential length L1of the groove portion211of the first circumferential groove21and the maximum circumferential length L2of the groove portion221of the second circumferential groove22have the relationship L1<L2, thus forming the relationship between the groove area A1of the first circumferential groove21and the groove area A2of the second circumferential groove22such that A1<A2. Specifically, the maximum circumferential length L1of the groove portion211of the first circumferential groove21and the maximum circumferential length L2of the groove portion221of the second circumferential groove22have the relationship 1.11≤L2/L1, and preferably have the relationship 1.20≤L2/L1. The upper limit of the ratio L2/L1is not particularly limited, but is restricted by other conditions.

MODIFIED EXAMPLE 2

FIG.6andFIG.7are explanatory diagrams illustrating modified examples of the tire illustrated inFIG.2. In these drawings, constituents that are the identical to constituents illustrated inFIG.2have identical reference signs, and explanations thereof are omitted.

In the configuration illustrated inFIG.2, the plurality of groove portions211constituting the first circumferential groove21are arranged with a predetermined pitch length P1all around the circumference of the tire, and the plurality of groove portions221constituting the second circumferential groove22are arranged with a predetermined pitch length P2all around the circumference of the tire. Additionally, the first and second groove portions211,221are arranged in a staggered manner in the tire circumferential direction with a predetermined phase difference φ. Such a configuration can preferably improve the tire wet performance while maintaining the tire traction performance.

In contrast, in the configuration inFIG.6, the first circumferential groove21includes a first groove unit U1including three or more groove portions211arranged with a predetermined pitch length P1in the tire circumferential direction, and a plurality of first groove units U1are arranged with a predetermined pitch length P1′ in the tire circumferential direction. Similarly, the second circumferential groove22includes a second groove unit U2including three or more groove portions221arranged with a predetermined pitch length P2in the tire circumferential direction, and a plurality of second groove units U2are arranged with a predetermined pitch length P2′ in the tire circumferential direction. Additionally, the first and second groove units U1and U2are arranged in a staggered manner in the tire circumferential direction with a predetermined phase difference φ′. Such a configuration can preferably improve the tire traction performance while maintaining the tire wet performance.

Additionally, inFIG.6, the pitch length P1‘of the first groove unit U1and the pitch length P2’ of the second groove unit U2have the relationships 0.10≤P1′/TL≤0.30 and 0.10≤P2′/TL≤0.30 with respect to the tire circumferential length TL (not illustrated). Additionally, the pitch length P1′ of the first groove unit U1and the pitch length P2′ of the second groove unit U2have the relationship 0.90≤P1′/P2′≤1.10, and preferably have the relationship 0.95≤P1′/P2′≤1.05.

Additionally, inFIG.6, the maximum circumferential length L1′ of the first groove unit U1and the maximum circumferential length L2′ of the second groove unit U2have the relationships 0.050≤L1′/TL≤0.100 and 0.050≤L2′/TL≤0.100 with respect to the tire circumferential length TL (not illustrated). In addition, the maximum circumferential length L1′ of the first groove unit U1and the maximum circumferential length L2′ of the second groove unit U2have the relationship 0.90≤L2′/L1′≤1.10, and preferably have the relationship 0.95≤L2′/L1′≤1.05.

Additionally, inFIG.6, the maximum circumferential length L1′ of the first groove unit U1and the maximum circumferential length L2′ of the second groove unit U2have the relationships 0.30≤L1′/P1′≤0.60 and 0.30≤L2′/P2′≤0.60, and preferably have the relationships 0.45≤L1′/P1′≤0.55 and 0.45≤L2′/P2′≤0.55 with respect to the pitch length P1′ of the first groove unit U1and the pitch length P2′ of the second groove unit U2.

Additionally, inFIG.6, a phase difference φ′ between the first groove unit U1and the second groove unit U2has the relationship 0.25≤φ′/P1′≤0.75, and preferably has the relationship 0.40≤φ′/P1′≤0.50 with respect to the pitch length P1′ of the first groove unit U1.

Additionally, in the configuration inFIG.6, as inFIG.2, the maximum groove width W1of the first circumferential groove21and the maximum groove width W2of the second circumferential groove22have the relationship W1<W2, thus forming the relationship between the groove area A1of the first circumferential groove21and the groove area A2of the second circumferential groove22such that A1<A2.

On the other hand, in the configuration inFIG.7, compared with the configuration inFIG.6, the number N1of groove portions211constituting the first groove unit U1is less than the number N2of groove portions221constituting the second groove unit U2(N1<N2), thus forming the relationship between the groove area A1of the first circumferential groove21and the groove area A2of the second circumferential groove22such that A1<A2. In addition, inFIG.7, the number N1of the groove portions211constituting the first groove unit U1is two, but may be at least one.

MODIFIED EXAMPLE 3

FIG.8is an explanatory diagram illustrating a modified example of the tire illustrated inFIG.2. In these drawings, constituents that are identical to constituents illustrated inFIG.2have identical reference signs, and explanations thereof are omitted.

In the configuration illustrated inFIG.2, each of the first and second circumferential grooves21,22includes a plurality of groove portions211,221arranged discontinuously in a row in the tire circumferential direction. Such a configuration preferably increases the ground contact area of the tire and can improve the tire traction performance while maintaining the tire wet performance.

In contrast, in the configuration inFIG.8, each of the first and second circumferential grooves21,22extends continuously in the tire circumferential direction. In such a configuration, compared with the configuration illustrated inFIG.2, the configuration as described above preferably increases the groove area of the tire and can improve the tire wet performance while maintaining the tire traction performance.

MODIFIED EXAMPLE 4

FIG.9is an explanatory diagram illustrating a modified example of the tire illustrated inFIG.2. In these drawings, constituents that are identical to constituents illustrated inFIG.2have identical reference signs, and explanations thereof are omitted.

In the configuration inFIG.2, as illustrated inFIG.3, the groove depths H1, H2of the first and second circumferential grooves21,22are set identical, while the relationship between the groove area A1of the first circumferential groove21and the groove area A2of the second circumferential groove22in the tread contact surface is formed such that A1<A2, thus forming the relationship between the groove volume V1of the first circumferential groove21and the groove volume V2of the second circumferential groove22such that V1<V2.

However, no such limitation is intended, and the relationship between the groove area A1of the first circumferential groove21and the groove area A2of the second circumferential groove22may be set such that the groove area A1and the groove area A1are substantially identical, while, as illustrated inFIG.9, the groove depths H1, H2of the first and second circumferential grooves21,22in the groove depth direction may have the relationship H1<H2, thus forming the relationship between the groove volume V1of the first circumferential groove21and the groove volume V2of the second circumferential groove22such that V1<V2.

Effect

As described above, the tire1includes the mounting direction indicator (not illustrated) that indicates the tire mounting direction with respect to a vehicle. Additionally, the tire1includes the first and second circumferential grooves21,22extending intermittently or continuously in the tire circumferential direction (seeFIG.2). Additionally, with the tire mounted on the vehicle, the second circumferential groove22is located further on the inner side than the first circumferential groove21in the vehicle width direction. Additionally, the groove volume V1of the first circumferential groove21and the groove volume V2of the second circumferential groove22have the relationship V1<V2.

In such a configuration, since the groove volume V2of the second circumferential groove22on the inner side in the vehicle width direction is greater than the groove volume V1of the first circumferential groove21on the outer side in the vehicle width direction (V1<V2), the groove volume in the inner region in the vehicle width direction of the tread surface is increased, which improves the tire wet performance, and the rigidity of the land portion in the outer region in the vehicle width direction is increased, which improves the tire traction performance on dry road surfaces. This has an advantage in that the tire wet performance and the traction performance on dry road surfaces are improved in a compatible manner.

Additionally, in the tire1, the groove volume V1of the first circumferential groove21and the groove volume V2of the second circumferential groove22have the relationship 1.11≤V2/V1≤2.00 (seeFIG.2). Accordingly, there is an advantage in that the effect of improving the wet performance and traction performance of the tire due to the difference between the groove volumes V1and V2of the circumferential grooves21and22described above can be appropriately obtained.

Additionally, in the tire1, the maximum groove width W1of the first circumferential groove21and the maximum groove width W2of the second circumferential groove22have the relationships 0.020≤W1/TW≤0.080 and 0.020≤W2/TW≤0.080 with respect to the tire ground contact width TW (seeFIG.2). The lower limit described above has the advantage of ensuring drainage properties of the circumferential grooves21,22. Additionally, the upper limit has the advantage of suppressing degradation of the traction performance due to the excessive width of the circumferential grooves21,22.

Additionally, in the tire1, the maximum groove depths H1, H2of the first and second circumferential grooves21,22are in the range of 2.5 mm or more and 5.0 mm or less. This has the advantage of appropriately setting the maximum groove depths H1, H2of the circumferential grooves21,22.

Additionally, in the tire1, the groove area A1of the first circumferential groove21and the groove area A2of the second circumferential groove22have the relationships 0.015≤A1/Sa≤0.100 and 0.015≤A2/Sa≤0.100 with respect to the area Sa of the tire ground contact region. This has the advantage of appropriately setting the groove areas A1, A2of the circumferential grooves21,22.

Additionally, in the tire1, no other grooves or recess portions having an opening area greater than 40 mm2are provided in the tire ground contact region (seeFIG.2). This has the advantage of ensuring the ground contact area of the tire and appropriately ensuring the effect of improving the traction performance of the tire described above.

Additionally, in the tire1, the groove area ratio of the tire ground contact region is in the range of 3.0% or more and 5.0% or less. This has the advantage of ensuring the traction characteristics of the tire, especially a race tire.

Additionally, in the tire1, the groove area A1of the first circumferential groove21and the groove area A2of the second circumferential groove22have the relationship A1<A2(seeFIG.2andFIGS.4to8). This has the advantage of efficiently forming the relationship between the groove volume V1of the first circumferential groove21and the groove volume V2of the second circumferential groove22such that V1<V2.

Additionally, in the tire1, the maximum depth H1of the first circumferential groove21and the maximum depth H2of the second circumferential groove22have the relationship H1<H2(seeFIG.9). This has the advantage of efficiently forming the relationship between the groove volume V1of the first circumferential groove21and the groove volume V2of the second circumferential groove22such that V1<V2.

Additionally, in the tire1, the first circumferential groove21is disposed in the outer region in the vehicle width direction, whereas the second circumferential groove22is disposed in the inner region in the vehicle width direction, the outer region and the inner region being demarcated by the tire equatorial plane CL (seeFIG.2). Compared with the configuration inFIG.4, the configuration as described above has the advantage of improving uneven wear resistance of the tire.

Additionally, in the tire1, each of the first and second circumferential grooves21,22includes the plurality of groove portions211,221arranged discontinuously in a row in the tire circumferential direction, and thus extends intermittently in the tire circumferential direction (seeFIG.2andFIGS.4to7). Compared with the configuration inFIG.8, the configuration as described above has the advantage of improving the traction performance of the tire.

Additionally, in the tire1, each of the first and second circumferential grooves21,22extends continuously in the tire circumferential direction (seeFIG.8). Compared with the configuration inFIG.2, the configuration as described above has the advantage of improving the wet performance of the tire.

Additionally, in the tire1, the tire cross-sectional height SH has the relationship 0.20≤SH/SW≤0.70 with respect to the total tire width SW, and the tire ground contact width TW has the relationship 0.90≤TW/SW≤0.98 with respect to the total tire width SW (seeFIG.1). This has the advantage of appropriately setting the aspect ratio SH/SW of the tire and the tire ground contact width TW.

Additionally, the tire1includes the pair of bead cores11,11, the carcass layer13extended across the pair of bead cores11,11, the pair of cross belts141,142disposed on the outer circumference of the carcass layer13, and the tread rubber15disposed on the outer side of the cross belts141,142in the radial direction (seeFIG.1). Additionally, the width Wb of the wider cross belt of the pair of cross belts141,142(the cross belt141on the inner diameter side inFIG.1) has the relationship 0.98≤Wb/TW≤1.10 with respect to the tire ground contact width TW. As a result, there is an advantage that the durability of the tire is appropriately secured.

Additionally, the tire1includes the pair of bead cores11,11, the carcass layer13extended across the pair of bead cores11,11, the pair of cross belts141,142disposed on the outer circumference of the carcass layer13, and the tread rubber15disposed on the outer side of the cross belts141,142in the radial direction (seeFIG.1). Additionally, the gauge Gr of the tread rubber15is in the range of 30% or more and 60% or less with respect to the total gauge Gt of the tread portion on the groove center lines of the first and second circumferential grooves21,22(seeFIG.3). This has the advantage of appropriately setting the gauge Gr of the tread rubber15.

EXAMPLES

FIGS.10and11are tables indicating the results of performance tests of tires according to embodiments of the technology.FIG.12is an explanatory diagram illustrating a test tire of Conventional Example illustrated inFIG.10.

In the performance tests, the (1) dry performance and (2) wet performance were evaluated for a plurality of types of test tires. Additionally, a test tire having a tire size of P205/50R15 84W was assembled on a rim specified by JATMA, and mounted on all wheels of a four-wheeled passenger car having a weight of 990 [kg]. In addition, the test tires were inflated to an internal pressure of 160 kPa in the cold and to an internal pressure of 220 kPa in the warm.

In the evaluation related to dry performance, the test vehicle ran four laps of a predetermined circuit of 3.7 km in an environment with clear weather, a road surface temperature of 18° C., and a temperature of 28° C., and the lap times were measured. The best lap time was used to express the results as index values for evaluation, with Conventional Example being assigned as the reference (100). In this evaluation, larger values are preferable.

In the evaluation related to the wet performance, the test vehicle ran four laps of the circuit of 3.7 km, sprinkled with water to a water depth of 1 mm, and the lap time was measured. The best lap time was used to express the results as index values for evaluation, with Conventional Example being assigned as the reference (100). In this evaluation, larger values are preferable. Moreover, an evaluation value of 99 or more indicates that the performance is appropriately maintained.

The test tires of the Examples have the configurations inFIGS.1to3, and the first circumferential groove21is disposed in the outer region in the vehicle width direction, and the second circumferential groove22is disposed in the inner region in the vehicle width direction, the outer region and the inner region being demarcated by the tire equatorial plane CL. Additionally, each of the first and second circumferential grooves21,22includes a plurality of groove portions211,221arranged discontinuously in a row in the tire circumferential direction. Additionally, the tire outer diameter is 586 mm, the tire cross-sectional height SH is 103 mm, the total tire width SW is 216 mm, the tire ground contact width TW is 202 mm, and the belt width Wb of the wider cross belt142is 203 mm. Additionally, the gauge Gr of the tread rubber15on the groove center lines X1and X2of the circumferential grooves21,22is in the range of 4.0 mm to 4.7 mm, and the total gauge Gt of the tread portion is in the range of 10 mm to 11 mm. Additionally, the groove widths W1and W2of the first and second circumferential grooves21,22have the relationship W1<W2, and for the groove depths H1, H2, H1=H2=3.3 mm. In addition, the distances D1, D2of the circumferential grooves21,22have the relationship D1/TW=D2/TW=0.25 with respect to the tire ground contact width TW.

The test tire of Conventional Example has the configuration illustrated inFIG.12, and differs from the test tire of Example 1 in that the first and second circumferential grooves are configured such that each groove extends continuously in the tire circumferential direction, and in that the first and second circumferential grooves have an identical groove width and an identical groove volume.

As can be seen from the test results, the test tires of Examples provide dry performance and wet performance of a tire in a compatible manner.