JP7205307B2 - pneumatic tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of achieving both dry performance and wet performance.

A conventional pneumatic tire achieves both dry performance and wet performance of the tire by providing non-penetrating lug grooves and sipes in land portions. As a conventional pneumatic tire adopting such a configuration, the technology described in Patent Document 1 is known.

JP 2017-52327 A

An object of the present invention is to provide a pneumatic tire that achieves both dry performance and wet performance.

In order to achieve the above object, a pneumatic tire according to the present invention includes a center main groove and shoulder main grooves extending in the tire circumferential direction, and a center land portion and shoulders partitioned by the center main groove and the shoulder main groove. A pneumatic tire comprising a land portion, wherein the shoulder land portion has a circumferential narrow groove extending continuously in the tire circumferential direction, and one end opening to the tire grounding end and the other end. and a second shoulder groove that opens into the shoulder main groove at one end and terminates in the shoulder land portion at the other end. , the first shoulder groove has a groove width of 1.5 [mm] or more and 4.0 [mm] or less and does not intersect the circumferential narrow groove, and the second shoulder groove has a width of 0.6 It has a groove width of [mm] or more and 1.2 [mm] or less, intersects the circumferential narrow groove, and the second shoulder groove is spaced apart from the first shoulder groove in the tire width direction. It is characterized by being arranged as follows.
A pneumatic tire according to the present invention includes a center main groove and shoulder main grooves extending in the tire circumferential direction, and a center land portion and a shoulder land portion partitioned by the center main groove and the shoulder main groove. In the pneumatic tire, the shoulder land portion includes a circumferential narrow groove extending continuously in the tire circumferential direction, and one end opening to the tire contact edge and the other end opening to the shoulder land portion. a first shoulder groove that terminates in a land portion; and a second shoulder groove that opens into the shoulder main groove at one end and terminates in the shoulder land portion at the other end, wherein the first shoulder The groove has a groove width of 1.5 [mm] or more and 4.0 [mm] or less and does not cross the circumferential narrow groove, and the second shoulder groove has a width of 0.6 [mm] or more. .2 [mm] or less, intersects the circumferential narrow grooves, and the first shoulder grooves and the second shoulder grooves are arranged in opposite directions to each other in the tire circumferential direction. It is characterized by being slanted.
A pneumatic tire according to the present invention includes a center main groove and shoulder main grooves extending in the tire circumferential direction, and a center land portion and a shoulder land portion partitioned by the center main groove and the shoulder main groove. In the pneumatic tire, the shoulder land portion includes a circumferential narrow groove extending continuously in the tire circumferential direction, and one end opening to the tire contact edge and the other end opening to the shoulder land portion. a first shoulder groove that terminates in a land portion; and a second shoulder groove that opens into the shoulder main groove at one end and terminates in the shoulder land portion at the other end, wherein the first shoulder The groove has a groove width of 1.5 [mm] or more and 4.0 [mm] or less and does not cross the circumferential narrow groove, and the second shoulder groove has a width of 0.6 [mm] or more. The groove width is 2 [mm] or less and intersects the circumferential narrow groove, and the center land portion is composed of a set of a first center groove, a second center groove and a third center groove. A plurality of sets of groove units are provided, and the first center groove, the second center groove and the third center groove are arranged without intersecting each other at an arrangement interval of 90 [deg] or more and 150 [deg] or less. The first center groove extends radially, has a groove width of 1.5 [mm] or more and 4.0 [mm] or less, and opens into the shoulder main groove at one end. It is characterized by terminating in the center land portion at the other end.

According to the pneumatic tire of the present invention, (1) since the shoulder land portion is provided with the circumferential narrow groove continuously extending in the tire circumferential direction, the configuration is provided with the circumferential narrow groove discontinuous in the tire circumferential direction. There is an advantage that the wet performance and snow performance of the tire are improved compared to . (2) Since the first shoulder grooves do not intersect the circumferential narrow grooves, the dry performance of the tire is ensured compared to a structure in which the first shoulder grooves intersect the circumferential narrow grooves. There is Furthermore, (3) the narrow second shoulder grooves intersect the circumferential narrow grooves, so that the dry performance of the tire is ensured, and at the same time, the wet performance and snow performance of the tire are improved.

FIG. 1 is a cross-sectional view of a pneumatic tire according to an embodiment of the invention taken along the tire meridian line. 2 is a plan view showing the tread surface of the pneumatic tire shown in FIG. 1. FIG. 3 is an enlarged view showing the tread of the pneumatic tire shown in FIG. 2. FIG. 4 is an enlarged plan view showing the groove unit of the center land portion shown in FIG. 3. FIG. FIG. 5 is a cross-sectional view in the groove depth direction showing the groove unit of the center land portion shown in FIG. 6 is an enlarged plan view showing the groove unit of the shoulder land portion shown in FIG. 3. FIG. 7 is a sectional view in the groove depth direction showing the groove unit of the shoulder land portion shown in FIG. 3. FIG. FIG. 8 is a chart showing results of performance tests of the pneumatic tire according to the embodiment of the invention. FIG. 9 is an explanatory diagram showing a conventional test tire. FIG. 10 is an explanatory diagram showing a test tire of a comparative example.

Hereinafter, the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious to replace. Moreover, the multiple modifications described in this embodiment can be arbitrarily combined within the scope obvious to those skilled in the art.

[Pneumatic tire]
FIG. 1 is a cross-sectional view of a pneumatic tire according to an embodiment of the invention taken along the tire meridian line. This figure shows a cross-sectional view of one side area in the tire radial direction. Moreover, the figure shows a radial tire for a passenger car as an example of a pneumatic tire.

In the figure, the cross section in the tire meridian direction refers to a cross section when the tire is cut along a plane including the tire rotation axis (not shown). Further, the symbol CL is the tire equatorial plane, which is a plane perpendicular to the tire rotation axis passing through the center point of the tire in the tire rotation axis direction. Moreover, the tire width direction refers to the direction parallel to the tire rotation axis, and the tire radial direction refers to the direction perpendicular to the tire rotation axis.

The pneumatic tire 1 has an annular structure around 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, and a tread rubber 15. , a pair of sidewall rubbers 16, 16 and a pair of rim cushion rubbers 17, 17 (see FIG. 1).

The pair of bead cores 11, 11 is an annular member formed by bundling a plurality of bead wires, and constitutes the cores of the left and right bead portions. The pair of bead fillers 12, 12 are arranged on the tire radial direction outer peripheries of the pair of bead cores 11, 11, respectively, to form a bead portion.

The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multilayer structure consisting of a plurality of laminated carcass plies. Constitute. Further, both ends of the carcass layer 13 are wound back outward in the tire width direction so as to wrap the bead core 11 and the bead filler 12 and are locked. The carcass plies of the carcass layer 13 are formed by coating a plurality of carcass cords made of steel or organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) with a coating rubber and rolling them. It has a carcass angle (defined as an inclination angle of the longitudinal direction of the carcass cords with respect to the tire circumferential direction) of [deg] or more and 95 [deg] or less.

The belt layer 14 is formed by laminating a pair of cross belts 141 and 142 and a belt cover 143, and is arranged around the outer periphery of the carcass layer 13. As shown in FIG. The pair of cross belts 141 and 142 is constructed by coating a plurality of belt cords made of steel or organic fiber material with coat rubber and rolling the cords, and has a belt angle of 20 [deg] or more and 55 [deg] or less in absolute value. have. The pair of cross belts 141 and 142 have belt angles of opposite signs (defined as inclination angles of the longitudinal direction of the belt cords with respect to the tire circumferential direction), and the longitudinal directions of the belt cords intersect each other. laminated together (so-called cross-ply structure). The belt cover 143 is configured by coating a belt cord made of steel or an organic fiber material with a coat rubber, and has a belt angle of 0 [deg] or more and 10 [deg] or less in absolute value. The belt cover 143 is, for example, a strip material made by coating one or more belt cords with a coating rubber. And it is configured by winding it spirally. Moreover, the belt cover 143 is arranged to cover the entire area of the cross belts 141 and 142 .

The tread rubber 15 is arranged on the outer periphery of the carcass layer 13 and the belt layer 14 in the tire radial direction to constitute the tread portion of the tire. A pair of sidewall rubbers 16, 16 are arranged outside the carcass layer 13 in the tire width direction, respectively, and constitute left and right sidewall portions. A pair of rim cushion rubbers 17, 17 are arranged radially inward of the left and right bead cores 11, 11 and the turn-up portions of the carcass layer 13, respectively, and constitute contact surfaces of the left and right bead portions with respect to the rim flange.

[Tread pattern]
2 is a plan view showing the tread surface of the pneumatic tire shown in FIG. 1. FIG. The figure shows the tread pattern of an all-season tire. In the figure, the tire circumferential direction refers to the direction around the tire rotation axis. Moreover, the code|symbol T is a tire contact edge.

As shown in FIG. 2, the pneumatic tire 1 includes a plurality of circumferential main grooves 21 and 22 extending in the tire circumferential direction, a plurality of land portions 31 partitioned by the circumferential main grooves 21 and 22, 32 are provided on the tread surface.

Here, the outermost left and right circumferential main grooves 22, 22 in the tire width direction are defined as shoulder main grooves, and the other circumferential main grooves 21 between these circumferential main grooves 22, 22 are defined as center grooves. Define as the main groove. Further, the left and right land portions 32, 32 on the outermost side in the tire width direction are defined as shoulder land portions, and the other land portions 31, 31 between these land portions 32, 32 are defined as the center land portion. . In addition, the region on the inner side in the tire width direction bounded by the left and right shoulder main grooves 22, 22 is defined as the center region, and the region on the outer side in the tire width direction is defined as the shoulder region.

The main groove is a groove that is required to display a wear indicator defined by JATMA, and has a groove width of 4.0 [mm] or more and a groove depth of 7.5 [mm] or more.

The groove width is measured as the maximum value of the distance between the left and right groove walls at the opening of the groove in an unloaded state in which the tire is mounted on a specified rim and filled with a specified internal pressure. In a configuration in which the land portion has a notch portion or a chamfered portion at the edge portion, the groove width is measured with reference to the intersection of the tread surface and the extension line of the groove wall in a cross-sectional view with the groove length direction as the normal direction. measured. In addition, in a configuration in which the groove extends in a zigzag or wavy shape in the tire circumferential direction, the groove width is measured with reference to the center line of the amplitude of the groove wall.

Groove depth is measured as the maximum distance from the tread surface to the groove bottom when the tire is mounted on a specified rim and filled with a specified internal pressure in an unloaded state. In addition, in a configuration in which the groove has partial irregularities or sipes at the groove bottom, the groove depth is measured excluding these.

The stipulated rim means the "applied rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. In addition, the prescribed internal pressure means the "maximum air pressure" prescribed by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" prescribed by TRA, or "INFLATION PRESSURES" prescribed by ETRTO. Moreover, the specified load means the "maximum load capacity" specified by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "LOAD CAPACITY" specified by ETRTO. However, according to JATMA, in the case of passenger car tires, the specified internal pressure is 180 [kPa] and the specified load is 88 [%] of the maximum load capacity.

For example, in the configuration of FIG. 2, the single center main groove 21 and the pair of shoulder main grooves 22, 22 are arranged symmetrically with respect to the tire equatorial plane CL. Further, the center main groove 21 is arranged on the tire equatorial plane CL. Four rows of land portions 31 and 32 are defined by these circumferential main grooves 21 and 22 .

However, the present invention is not limited to this, and four or more circumferential main grooves may be arranged, or the circumferential main grooves may be arranged asymmetrically with respect to the tire equatorial plane CL (not shown). Further, the land portion may be positioned on the tire equatorial plane CL by arranging one circumferential main groove at a position off the tire equatorial plane CL (not shown).

Moreover, in the structure of FIG. 2, the circumferential main grooves 21 and 22 have a straight shape. However, the present invention is not limited to this, and the circumferential main grooves 21 and 22 may have a zigzag shape or a wavy shape having amplitude in the tire width direction (not shown).

In addition, in the configuration of FIG. 2, the pneumatic tire 1 has a tread pattern that is symmetrical about a point on the tire equatorial plane CL. However, the present invention is not limited to this, and the pneumatic tire 1 may have, for example, a symmetrical tread pattern centered on the tire equatorial plane CL or an asymmetrical tread pattern. (illustration omitted).

[Center land groove unit]
3 is an enlarged view showing the tread of the pneumatic tire shown in FIG. 2. FIG. The figure shows one side area of the tread bounded by the tire equatorial plane CL. 4 and 5 are an enlarged plan view (FIG. 4) and a sectional view in the groove depth direction (FIG. 5) showing the groove unit of the center land portion shown in FIG. Moreover, FIG. 5 shows a sectional view in the groove depth direction along the first center groove 41 and the third center groove 43 of the groove unit 4ce.

As shown in FIG. 3, the center land portion 31 includes a plurality of sets of groove units 4ce. The groove unit 4ce is configured with a first center groove 41, a second center groove 42 and a third center groove 43 as a set. Moreover, a plurality of sets of groove units 4ce are arranged at predetermined intervals in the tire circumferential direction. These center grooves 41 to 43 ensure wet performance of the tire.

Moreover, as shown in FIG. 4, the first center groove 41, the second center groove 42 and the third center groove 43 are arranged without intersecting each other. That is, the three center grooves 41-43 are separated from each other and do not communicate with each other. Therefore, the center land portion 31 is not divided by the center grooves 41 to 43 of the groove unit 4ce, and has a continuous tread surface in the tire circumferential direction. As a result, the rigidity of the center land portion 31 is ensured, and the steering stability performance of the tire on a dry road surface is improved.

Also, the first center groove 41, the second center groove 42, and the third center groove 43 radially extend at an arrangement interval of 90 [deg] or more and 150 [deg] or less. Specifically, the angle α between the first center groove 41 and the second center groove 42, the angle β between the second center groove 42 and the third center groove 43, the third center groove 43 and the first center groove 41 are in the range of 90 [deg] or more and 150 [deg] or less. Also, it is preferable that the angles α to γ are in the range of 105 [deg] to 135 [deg]. By arranging the center grooves 41 to 43 of the groove unit 4ce radially at predetermined intervals in this way, the rigidity of the center land portion 31 is properly increased compared to a configuration in which the center grooves 41 to 43 are unevenly distributed. It is ensured and the dry performance of the tire is efficiently improved.

Further, other grooves or sipes are arranged in a region (not shown) surrounding the outer circumference of the groove unit 4ce, specifically, a triangular region connecting the ends of the three center grooves 41 to 43. Instead, the land portion 31 has a continuous tread surface. As a result, the rigidity of the center land portion 31 is efficiently secured, and the dry performance of the tire is efficiently improved. Also, the snow performance of the tire is improved.

The angle formed by adjacent grooves is defined as the angle formed by imaginary lines connecting both ends of the grooves.

The first center groove 41 is a lug groove having a groove width Wg1 (see FIG. 4) of 1.5 [mm] or more and 4.0 [mm] or less, and extends mainly in the tire width direction. Moreover, it is preferable that the groove width Wg1 of the first center groove 41 is in the range of 1.7 [mm]≦Wg1≦2.5 [mm]. In addition, the first center groove 41 is open at the tire ground contact surface to exhibit drainage action and edge action, thereby improving wet performance and snow performance of the tire. The first center groove 41 has a semi-closed structure in which one end opens into the shoulder main groove 22 and the other end terminates within the center land portion 31 . Since the first center groove 41 opens into the shoulder main groove 22, the drainage action and snow performance of the first center groove 41 are improved.

The contact patch of a tire is defined as the contact surface between the tire and a flat plate when the tire is mounted on a specified rim, given a specified internal pressure, placed vertically against a flat plate in a stationary state, and a load corresponding to the specified load is applied. Defined as the contact surface.

The second center groove 42 is a narrow groove or sipe having a groove width of 0.6 [mm] or more and 1.2 [mm] or less, and extends mainly in the tire circumferential direction. Moreover, it is preferable that the second center groove 42 has a sipe that has a groove width Wg2 of less than 1.0 [mm] and closes at the tire contact surface. In addition, the second center groove 42 enhances the wet performance of the tire by absorbing water on a wet road surface. In addition, the second center groove 42 increases the adsorption action on the snow-covered road surface and the ice-covered road surface, thereby improving the snow performance and the ice performance of the tire. In addition, the second center groove 42 has a closed structure that terminates within the center land portion 31 at the left and right ends. Since the second center groove 42 extending in the tire circumferential direction has a groove width narrower than that of the first center groove 41, the rigidity of the center land portion 31 is properly ensured and the dryness of the tire is improved. .

Thin grooves and sipes are distinguished from each other in that the thin grooves open at the contact patch of the tire and the sipes close at the contact patch of the tire.

The third center groove 43 is a lug groove, a narrow groove, or a sipe having a groove width Wg3 of 0.6 [mm] or more and 2.0 [mm] or less, and extends mainly in the tire width direction. Further, the third center groove 43 has a semi-closed structure in which one end opens to the center main groove 21 and the other end terminates within the center land portion 31 . A third center groove 43 extends from the inside of the center land portion 31 to a different side from the first center groove 41 and opens into the center main groove 21 on the tire equatorial plane CL side of the center land portion 31 . .

Further, the groove width Wg1 of the first center groove 41, the groove width Wg2 of the second center groove 42, and the groove width Wg3 of the third center groove 43 have a relationship of Wg2<Wg1 and Wg3<Wg1. That is, the groove width Wg1 of the first center groove 41, which is a lug groove, is the widest. As a result, the function of the first center groove 41 as a lug groove is effectively exhibited, and the wet performance of the tire is improved.

On the other hand, the groove width Wg2 of the second center groove 42, the groove width Wg1 of the first center groove 41, and the groove width Wg3 of the third center groove 43 have a relationship of Wg2<Wg3 and Wg2<Wg1. That is, the groove width Wg2 of the second center groove 42 extending mainly in the tire circumferential direction is the narrowest. Moreover, it is preferable that the difference between the groove widths Wg1 to Wg3 is 0.1 [mm] or more. Thereby, the rigidity of the center land portion 31 is ensured, and the dry performance of the tire is ensured.

For example, in the configuration of FIG. 4, the second center groove 42 and the third center groove 43 are narrow grooves or sipes having groove widths Wg2 and Wg3 of 1.2 [mm] or less, and the grooves of the first center groove 41 It has groove widths Wg2 and Wg3 narrower than the width Wg1. Such a configuration is preferable in that the rigidity of the center land portion 31 is ensured and the dry performance of the tire is improved.

In FIG. 4, the inclination angle θ1 of the first center groove 41 with respect to the tire circumferential direction is preferably in the range of 30 [deg] ≤ θ1 ≤ 60 [deg], and 40 [deg] ≤ θ1 ≤ 50 [deg]. ] is more preferable. As a result, the drainage action of the first center groove 41 is improved, and the function of the first center groove 41 as a lug groove is ensured.

In addition, the inclination angle θ2 of the second center groove 42 with respect to the tire circumferential direction is preferably in the range of 0 [deg] ≤ θ2 ≤ 30 [deg], and is in the range of 0 [deg] ≤ θ2 ≤ 20 [deg]. It is more preferable to have At this time, the second center groove 42 may be inclined toward the first center groove 41 side from the central portion of the groove unit 4ce toward the peripheral portion (see FIG. 4), or conversely, the third center groove 43 side. (illustration omitted).

The inclination angle of the groove is an angle between each imaginary line connecting both ends of the groove and the tire circumferential direction, and is defined in the range of 0 [deg] to 90 [deg].

Further, the inclination angle θ2 of the second center groove 42 with respect to the tire circumferential direction, the inclination angle θ1 with respect to the tire circumferential direction of the first center groove 41, and the inclination angle θ3 with respect to the tire circumferential direction of the third center groove 43 satisfy θ2<θ1. Moreover, there is a relationship of θ2<θ3. That is, the second center groove 42 extends mainly in the tire circumferential direction, and as a result, the other grooves 41 and 43 extend mainly in the tire width direction under the restrictions of the angles α, β, and γ of the arrangement intervals. exist.

For example, in the configuration of FIG. 4, the first center groove 41, the second center groove 42, and the third center groove 43 have their terminal ends opposed to each other at the central portion of the center land portion 31, and radially centered on this position. extended. Further, the first center groove 41 is inclined at an inclination angle θ1 with respect to the tire circumferential direction and opens into the shoulder main groove 22 located on the outer side in the tire width direction (see FIG. 3). Further, the third center groove 43 is inclined at an inclination angle θ2 in the opposite direction to the first center groove 41 and opens into the center main groove 21 on the tire equatorial plane CL side. Therefore, the first center groove 41 and the third center groove 43 are arranged in a V shape that protrudes in the tire circumferential direction. Further, the second center groove 42 extends in the V-shaped convex direction of the first center groove 41 and the third center groove 43 at an inclination angle θ2. As a result, the second center groove 42 extends in the tire circumferential direction at the central portion of the center land portion 31, and the first center groove 41 and the third center groove 43 extend in the tire width direction around the second center groove 42. It extends left and right.

Further, as shown in FIG. 4, two other second center grooves 42 and a third center groove 43 are arranged close to one first center groove 41 . Specifically, the distance Da between the first center groove 41 and the second center groove 42 and the distance Db between the first center groove 41 and the third center groove 43 are 1.0 [mm] ≤ Da ≤ 5. .0 [mm] and 1.0 [mm] ≤ Db ≤ 5.0 [mm]. The range of the distance Dc (the dimension symbol is omitted in the drawing) between the second center groove 42 and the third center groove 43 is not particularly limited, but is 1.0 [mm] ≤ 1.0 [mm] as with the other distances Da and Db. It is preferable to be in the range of Dc≦5.0 [mm].

The distance between adjacent grooves is measured as the tread footprint distance.

For example, in the configuration of FIG. 4, as described above, the three center grooves 41 to 43 face each other at the central portion of the center land portion 31, and extend radially around this position. there is Also, the first center groove 41 and the second center groove 42 are spaced apart from each other in the tire circumferential direction and do not overlap each other in the tire circumferential direction. Also, the first center groove 41 and the second center groove 42 are closest to each other at the end portions of the grooves 41 and 42 in the center land portion 31 . Therefore, the distance Da between adjacent grooves 41 and 42 is measured as the distance between the end portions of grooves 41 and 42 .

Also, the first center groove 41 and the third center groove 43 are spaced apart from each other in the tire width direction and do not overlap each other in the tire width direction. Also, the first center groove 41 and the third center groove 43 are closest to each other at the end portions of the grooves 41 and 42 in the center land portion 31 . Therefore, the distance Db between adjacent center grooves 41 and 43 is measured as the distance between the end portions of center grooves 41 and 43 . In the above configuration, the first center groove 41, the second center groove 42, and the third center groove 43 are arranged at mutually different positions in the tire circumferential direction or the tire width direction. It is preferable in that the effect can be obtained efficiently.

Further, the second center groove 42 and both the first center groove 41 and the third center groove 43 are separated from each other in the tire circumferential direction and do not overlap each other in the tire circumferential direction. Further, the third center groove 43, the first center groove 41 and the second center groove 42 are separated from each other in the tire width direction and do not overlap in the tire width direction. Such a configuration is preferable in that the effects of the second center groove 42 and the third center groove 43 can be obtained efficiently.

Furthermore, the first center groove 41 and the third center groove 43 are arranged to incline in mutually different directions in the tire circumferential direction and overlap each other in the tire circumferential direction. As described above, since the angle γ formed by the first center groove 41 and the third center groove 43 is in the range of 90 [deg] or more and 150 [deg] or less, the first center groove 41 is positioned with respect to the tire circumferential direction. By inclining at the predetermined angle θ1, the first center groove 41 and the third center groove 43 necessarily have the above positional relationship.

4, the second center groove 42 is inclined toward the first center groove 41, so that the second center groove 42 and the first center groove 41 overlap each other in the tire width direction. Also, the second center groove 42 and the third center groove 43 do not overlap each other in the tire width direction. However, not limited to this, the second center groove 42 and the third center groove 43 may overlap each other in the tire width direction by tilting the second center groove 42 toward the third center groove 43 side. (illustration omitted).

Further, in FIG. 4, the extension length L1 of the first center groove 41 in the tire width direction and the width Wce of the center land portion 31 have a relationship of 0.40≦L1/Wce≦0.80. It is preferable to have a relationship of 0.50≦L1/Wce≦0.70. As a result, the extension length L1 of the first center groove 41 is optimized.

The circumferential extension length L2 of the second center groove 42 and the width Wce of the center land portion 31 preferably have a relationship of 0.20≤L2/Wce≤0.50, and 0.20≤0.20. It is more preferable to have a relationship of L2/Wce≦0.30. Thereby, the extension length L2 of the second center groove 42 is optimized.

Although the extension length L3 of the third center groove 43 in the tire width direction (the reference numerals are omitted) is not particularly limited, the extension length L1 of the first center groove 41 and the first center groove 41 and the third center groove 43 and the relationship between the distance Db between the first center groove 41 and the third center groove 43 .

The extension lengths L1 and L3 of the first center groove 41 and the third center groove 43 are measured as the distances in the tire width direction between the end portions of the grooves 41 and 43 and the openings for the center main groove 21 and the shoulder main grooves 22. be done. Further, the extension length L2 of the second center groove 42 is measured as the distance between both end portions of the groove 42 in the tire circumferential direction.

The width of the land portion is measured as the width of the contact area of the land portion when the tire is mounted on a specified rim, given a specified internal pressure, and in an unloaded state.

In the configuration of FIG. 4, all of the center grooves 41 to 43 of the groove unit 4ce have a straight shape. However, the shape is not limited to this, and each of the center grooves 41 to 43 may optionally have an arc shape, wave shape, zigzag shape, or the like (not shown). For example, the second center groove 42 or the third center groove 43 may be a sipe having a zigzag shape.

5, the groove depth Hm of the center main groove 22 and the groove depth H1 of the first center groove 41 have a relationship of 0.50≦H1/Hm≦0.90. Further, the groove depth H1 of the first center groove 41, the groove depth H2 of the second center groove 42, and the groove depth H3 of the third center groove 43 have a relationship of H2<H1 and H3<H1. Therefore, the groove depth H1 of the first center groove 41 is the deepest compared to the other grooves 42 and 43 . Thereby, the groove depth H1 of the first center groove 41 is optimized.

Further, the groove depth Hm of the center main groove 22 and the groove depth H2 of the second center groove 42 have a relationship of 0.20≦H2/Hm≦0.50. Further, the groove depth H2 of the second center groove 42, the groove depth H1 of the first center groove 41, and the groove depth H3 of the third center groove 43 have a relationship of H2<H3 and H2<H1. Therefore, the groove depth H2 of the second center groove 42 is the shallowest compared to the other grooves 41 and 43 . Moreover, it is preferable that the groove depth H2 of the second center groove 42 is in the range of 1.5 [mm]≦H2. Thereby, the groove depth H2 of the shallowest second center groove 42 is properly ensured.

[Groove unit of shoulder land part]
6 and 7 are an enlarged plan view (FIG. 6) and a sectional view in the groove depth direction (FIG. 7) showing the groove unit of the shoulder land portion shown in FIG. 7 shows a cross-sectional view in the groove depth direction along the first shoulder groove 44 and the second shoulder groove 45. As shown in FIG.

As shown in FIG. 3, the shoulder land portion 32 includes a circumferential narrow groove 23 and first to third shoulder grooves 44-46.

The circumferential narrow grooves 23 are narrow grooves that continuously extend in the tire circumferential direction, and extend parallel to the tire circumferential direction with respect to the tire circumferential direction. Also, the circumferential narrow groove 23 has a sufficiently narrow groove width Wgs with respect to the shoulder main groove 22 (see FIG. 3). Further, it is preferable that the groove width Wgs of the circumferential narrow groove 23 and the groove width Wgm of the shoulder main groove 22 have a relationship of 0.10≦Wgs/Wgm≦0.40. Moreover, it is preferable that the groove width Wgs of the circumferential narrow groove 23 is in the range of 1.0 [mm]≦Wgs≦4.0 [mm]. Further, it is preferable that the groove depth Hs (see FIG. 7) of the circumferential narrow grooves 23 and the groove depth Hm of the shoulder main grooves 22 have a relationship of 0.30≦Hs/Hm≦0.70. Thereby, the groove width Wgs and the groove depth Hs of the circumferential narrow groove 23 are optimized.

6, the distance Ds from the edge portion of the shoulder land portion 32 on the shoulder main groove 22 side to the groove center line of the circumferential narrow groove 23 is 0.10≦Ds with respect to the width Wsh of the shoulder land portion 32. /Wsh≦0.40, and more preferably 0.15≦Ds/Wsh≦0.30.

Further, in the configuration of FIG. 3, the shoulder land portion 32 does not have another circumferential narrow groove in the region between the circumferential narrow groove 23 and the tire grounding edge T. As shown in FIG. For this reason, the shoulder land portion 32 has a wide tread surface that is continuous in the tire width direction, and the area between the circumferential narrow groove 23 and the tire ground contact edge T is not partitioned by other circumferential narrow grooves. are doing. In addition, the other circumferential narrow grooves are narrow grooves having an inclination angle of 0 [deg] or more and 20 [deg] or less with respect to the tire circumferential direction and a groove width of 4.0 [mm] or less. Defined.

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

In the above configuration, since the shoulder land portion 32 includes the circumferential narrow grooves 23 continuously extending in the tire circumferential direction, the configuration includes the circumferential narrow grooves discontinuous in the tire circumferential direction (see FIG. 9 to be described later). Compared to , the drainage performance of the shoulder land portion 32 and the edge component in the tire width direction are increased. This improves the wet and snow performance of the tire.

The first shoulder groove 44 is a lug groove having a semi-closed structure, and is open at one end to the tire contact edge T, extends in the tire width direction, and extends into the shoulder land portion 32 at the other end. terminate with . Also, the end portion of the first shoulder groove 44 is located in the region between the circumferential narrow groove 23 and the tire ground contact edge T, and therefore the first shoulder groove 44 does not intersect the circumferential narrow groove 23 .

In the above configuration, the first shoulder grooves 44 do not intersect the circumferential narrow grooves 23, so compared with the configuration in which the first shoulder grooves 44 intersect the circumferential narrow grooves 23 (see FIG. 10 described later). Therefore, the rigidity of the shoulder land portion 32 is ensured. This ensures the dry performance of the tire.

Further, the first shoulder groove 44 has a groove width Wg4 (see FIG. 6) of 1.5 [mm] or more and 4.0 [mm] or less. Further, the groove depth H4 (see FIG. 7) of the first shoulder groove 44 and the groove depth Hm of the shoulder main groove 22 have a relationship of 0.50≦H4/Hm≦0.90. Further, as shown in FIG. 7 , the groove depth H4 of the first shoulder groove 44 is deeper than the groove depth of the circumferential narrow groove 23 .

6, the extension length L4 of the first shoulder groove 44 in the ground contact surface of the shoulder land portion 32 is 0.30≦L4/Wsh≦0.50 with respect to the width Wsh of the shoulder land portion 32. It is preferable to have a relationship of 0.35≦L4/Wsh≦0.45. Further, the inclination angle θ4 of the first shoulder groove 44 with respect to the tire circumferential direction is in the range of 50 [deg]≦θ4≦88 [deg].

6, the distance Ds of the circumferential narrow groove 23 and the extension length L4 of the first shoulder groove 44 are 0.40≦(Wsh−Ds−L4)/Wsh with respect to the width Wsh of the shoulder land portion. and more preferably 0.45≦(Wsh−Ds−L4)/Wsh. Thereby, the distance from the end portion of the first shoulder groove 44 to the circumferential narrow groove 23 is properly secured. The upper limit of the ratio (Wsh-Ds-L4)/Wsh is not particularly limited, but is restricted by the range of the distance Ds and the extension length L4.

Further, the width Wce of the center region and the width Wsh of the shoulder land portion 32 are in the range of 20% or more and 50% or less of the tire contact width TW (see FIG. 2). Thereby, the width Wce and the width Wsh of each land portion 31, 32 are optimized.

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

The second shoulder grooves 45 are sipes or narrow grooves having a semi-closed structure, open into the shoulder main groove 22 at one end, extend in the tire width direction, and form a shoulder land at the other end. It terminates in section 32 . Also, the end portion of the second shoulder groove 45 is located in the region between the circumferential narrow groove 23 and the tire ground contact edge T, and therefore the second shoulder groove 45 intersects the circumferential narrow groove 23 .

In the above-described configuration, the narrow second shoulder groove 45 intersects the circumferential narrow groove 23 , thereby suppressing a decrease in rigidity of the shoulder land portion 32 , and extending the distance from the shoulder main groove 22 to the first shoulder groove 44 . The drainage performance in the region up to the end portion and the edge component in the tire circumferential direction are ensured. This ensures the dry performance of the tire and at the same time improves the wet and snow performance of the tire.

Further, the second shoulder groove 45 has a groove width Wg5 (see FIG. 6) of 0.6 [mm] or more and 1.2 [mm] or less. Further, the groove depth H5 (see FIG. 7) of the second shoulder groove 45 has a relationship of 0.30≦H5/Hm≦0.70 with respect to the groove depth Hm of the shoulder main groove 22 . Further, as shown in FIG. 7 , the groove depth H5 of the second shoulder groove 45 is deeper than the groove depth of the circumferential narrow groove 23 and shallower than the groove depth H4 of the first shoulder groove 44 .

Moreover, it is preferable that the second shoulder groove 45 is a sipe that closes when the tire touches the ground. As a result, the rigidity of the shoulder land portion 32, particularly the rigidity of the narrow ribs (reference numerals omitted in the drawing) defined by the circumferential narrow grooves 23 and the shoulder main grooves 22 when the tire touches the ground is ensured.

Moreover, in the configuration of FIG. 6, the second shoulder groove 45 has a linear shape. However, not limited to this, the second shoulder groove 45 may have a gentle arc shape (not shown).

Further, as shown in FIG. 6, the second shoulder grooves 45 are spaced apart from the first shoulder grooves 44 in the tire width direction and arranged so as not to overlap each other in the tire width direction. Moreover, the distance Dc between the second shoulder groove 45 and the first shoulder groove 44 is in the range of 1.0 [mm]≦Dc≦5.0 [mm]. The length of the second shoulder grooves 45 extending in the tire width direction (the dimension symbols are omitted in the drawing) is not particularly limited, but the distance between the distance Dc and the length L4 of the first shoulder grooves 44 extends. Restricted by relationships.

In the above configuration, the second shoulder grooves 45 are spaced apart from the first shoulder grooves 44, so that a ventilation path is secured in the tire vulcanization molding process, and vulcanization failure of the tire is suppressed. . Moreover, since the second shoulder grooves 45 are arranged close to the first shoulder grooves 44, the drainage performance of the shoulder land portion 32 is improved.

In FIG. 6, the inclination angle θ5 of the second shoulder groove 45 with respect to the tire circumferential direction is preferably in the range of 30[deg]≦θ5≦60[deg], and 40[deg]≦θ5≦50[deg]. ] is more preferable. Further, the inclination angle θ5 of the second shoulder groove 45 and the inclination angle θ4 of the first shoulder groove 44 have a relationship of θ5<θ4.

Further, as shown in FIG. 6, the first shoulder groove 44 and the second shoulder groove 45 are inclined in opposite directions to each other with respect to the tire circumferential direction. With such a configuration, steering stability performance (particularly turning performance) of the tire is improved compared to a configuration in which the first shoulder groove 44 and the second shoulder groove 45 are inclined in the same direction. Also, the angle δ between the first shoulder groove 44 and the second shoulder groove 45 is preferably in the range of 120 [deg] ≤ δ ≤ 160 [deg], more preferably 130 [deg] ≤ δ ≤ 150 [deg]. A range is more preferred.

The third shoulder groove 46 is a sipe or narrow groove having a semi-closed structure, and is open at one end to the tire contact edge T, extends in the tire width direction, and forms a shoulder land portion at the other end. 32 terminates. In addition, the end portion of the third shoulder groove 46 is located in the region between the circumferential narrow groove 23 and the tire ground contact edge T, and therefore the third shoulder groove 46 does not intersect the circumferential narrow groove 23 . Further, the third shoulder groove 46 has a groove width of 0.6 [mm] or more and 2.0 [mm] or less (dimension symbols are omitted in the drawing). Further, the groove depth of the third shoulder grooves 46 (dimension symbols omitted in the drawing) is in the range of 30% or more and 60% or less of the groove depth Hm of the shoulder main grooves 22 .

6, the extension length L6 of the third shoulder groove 46 in the ground contact surface of the shoulder land portion 32 is 0.35≦L6/Wsh≦0.65 with respect to the width Wsh of the shoulder land portion 32. It is preferable to have a relationship of 0.40≦L6/Wsh≦0.60. It is preferable that the extension length L6 of the third shoulder groove 46 and the extension length L4 of the first shoulder groove 44 have a relationship of 1.10≦L6/L4≦1.25.

Further, the inclination angle θ6 of the third shoulder groove 46 with respect to the tire circumferential direction is in the range of 50 [deg]≦θ6≦88 [deg]. Moreover, it is preferable that the inclination angle θ4 of the first shoulder groove 44 is in the range of -10 [deg] ≤ θ6 - θ4 ≤ 10 [deg]. Therefore, the third shoulder grooves 46 are arranged substantially parallel to the first shoulder grooves 44 .

3, the first center groove 41 of the center land portion 31 is arranged offset from the first shoulder groove 44 of the shoulder land portion 32 in the tire circumferential direction. Specifically, when the first center groove 41 of the center land portion 31 and the first shoulder groove 44 of the shoulder land portion 32 are projected in the tire width direction, they are arranged so as not to overlap each other. . This reduces pattern noise due to the arrangement of the relatively wide grooves 41, 44 and improves the noise performance of the tire.

Further, as shown in FIG. 3 , the second shoulder groove 45 of the shoulder land portion 32 extends along the extension line of the groove centerline of the first center groove 41 of the center land portion 31 . Specifically, the second shoulder grooves 45 are inclined in the same direction with respect to the first center groove 41 , and the second shoulder grooves 45 are arranged substantially parallel to the first center groove 41 . Further, the distance Dp of the second shoulder groove 45 to the extension line of the groove center line of the first center groove 41 is 0≤Dp/Wg1≤2. 00 relationship. As a result, when the tire is rolling, the drainage from the first center groove 41 of the center land portion 31 to the third center groove 43 of the shoulder land portion 32 is improved, and the wet performance of the tire is improved. In the configuration of FIG. 3, the first center groove 41 and the second shoulder groove 45 have linear shapes, but they may have arc shapes (not shown).

[effect]
As described above, the pneumatic tire 1 includes the center main groove 21 and the shoulder main groove 22 extending in the tire circumferential direction, and the center land portion 31 and the shoulder main groove 22 that are divided into the center main groove 21 and the shoulder main groove 22. and a land portion 32 (see FIG. 2). In addition, the shoulder land portion 32 has a circumferential narrow groove 23 extending continuously in the tire circumferential direction, and an opening at one end to the tire contact edge T and an opening inside the shoulder land portion 32 at the other end. and a second shoulder groove 45 that opens into the shoulder main groove 22 at one end and ends in the shoulder land portion 32 at the other end (see FIG. 6). ). Further, the first shoulder groove 44 has a groove width Wg4 of 1.5 [mm] or more and 4.0 [mm] or less and does not cross the circumferential narrow groove 23 . Further, the second shoulder groove 45 has a groove width Wg5 of 0.6 [mm] or more and 1.2 [mm] or less and intersects the circumferential narrow groove 23 .

In such a configuration, (1) the shoulder land portion 32 includes the circumferential narrow grooves 23 continuously extending in the tire circumferential direction, so that a configuration including the circumferential narrow grooves discontinuous in the tire circumferential direction (see FIG. 9 to be described later) is provided. ), the drainage performance of the shoulder land portion 32 and the edge component in the tire width direction are increased. This has the advantage of improving the wet performance and snow performance of the tire. (2) Since the first shoulder grooves 44 do not intersect the circumferential narrow grooves 23, the first shoulder grooves 44 do not intersect the circumferential narrow grooves 23 (see FIG. 10, which will be described later). Therefore, the rigidity of the shoulder land portion 32 is ensured. This has the advantage of ensuring the dry performance of the tire. Furthermore, (3) the narrow second shoulder groove 45 intersects the circumferential narrow groove 23 , thereby suppressing a decrease in rigidity of the shoulder land portion 32 , and allowing the first shoulder groove 44 to extend from the shoulder main groove 22 . The drainage performance in the region up to the end portion and the edge component in the tire circumferential direction are ensured. This has the advantage of ensuring the dry performance of the tire and simultaneously improving the wet performance and snow performance of the tire.

Further, in the pneumatic tire 1, the groove width Wgs of the circumferential narrow grooves 23 has a relationship of 0.10≦Wgs/Wgm≦0.40 with respect to the groove width Wgm of the shoulder main grooves 22 (see FIG. 3). ). There is an advantage that the function of the circumferential narrow groove 23 is ensured by the above lower limit, and the rigidity of the shoulder land portion 32 is ensured by the above upper limit.

Further, in the pneumatic tire 1, the groove depth Hs of the circumferential narrow grooves 23 has a relationship of 0.30≦Hs/Hm≦0.70 with respect to the groove depth Hm of the shoulder main grooves 22 (Fig. 7). There is an advantage that the function of the circumferential narrow groove 23 is ensured by the above lower limit, and the rigidity of the shoulder land portion 32 is ensured by the above upper limit.

In the pneumatic tire 1, the distance Ds from the edge portion of the shoulder land portion 32 on the shoulder main groove 22 side to the groove center line of the circumferential narrow groove 23 is greater than the width Wsh of the ground contact area of the shoulder land portion 32. 0.10≦Ds/Wsh≦0.40 (see FIG. 6). The above lower limit secures the rigidity of the narrow rib (reference numerals omitted in the figure) partitioned between the circumferential narrow groove 23 and the shoulder main groove 22, and the above upper limit ensures the circumferential narrow groove 23 and the first shoulder groove. 44 approaching each other, the decrease in rigidity of the shoulder land portion 32 is suppressed.

Further, in the pneumatic tire 1, the shoulder land portion 32 does not have other circumferential narrow grooves in the region between the circumferential narrow grooves 23 and the tire ground contact edge T (see FIG. 3). Thereby, there is an advantage that the rigidity of the shoulder land portion 32 is ensured.

Further, in the pneumatic tire 1, the extension length L4 of the first shoulder groove 44 in the ground contact surface of the shoulder land portion 32 is 0.30≦L4/Wsh with respect to the width Wsh of the ground contact area of the shoulder land portion 32. It has a relationship of Wsh≦0.50 (see FIG. 6). The above lower limit ensures the drainage effect of the first shoulder groove 44, and the above upper limit has the advantage of suppressing a decrease in rigidity of the shoulder land portion 32 caused by excessive extension length L4 of the first shoulder groove 44. be.

Further, in the pneumatic tire 1, the width Wsh of the shoulder land portion 32 has a relationship of 0.15≦Wsh/TW≦0.35 with respect to the tire contact width TW (see FIG. 2). Accordingly, there is an advantage that the width Wsh of the shoulder land portion 32 is optimized.

Further, in the pneumatic tire 1, the inclination angle θ4 of the first shoulder groove 44 with respect to the tire circumferential direction is in the range of 50 [deg]≦θ4≦85 [deg] (see FIG. 6). Accordingly, there is an advantage that the inclination angle θ4 of the first shoulder groove 44 is optimized.

Further, in the pneumatic tire 1, the second shoulder grooves 45 are arranged apart from the first shoulder grooves 44 in the tire width direction. In this configuration, the second shoulder grooves 45 are arranged apart from the first shoulder grooves 44, so that the ventilation path in the tire vulcanization molding process is secured, and the vulcanization failure of the tire is suppressed. There is

Further, in this pneumatic tire 1, the distance Dc between the second shoulder groove 45 and the first shoulder groove 44 is in the range of 1.0 [mm]≤Dc≤5.0 [mm]. This has the advantage of optimizing the distance Dc between the second shoulder groove 45 and the first shoulder groove 44 . In particular, due to the above upper limit, the second shoulder groove 45 is arranged close to the first shoulder groove 44, so that the shoulder land portion 32 has improved drainage performance.

Further, in the pneumatic tire 1, the first shoulder grooves 44 and the second shoulder grooves 45 are inclined in opposite directions to each other with respect to the tire circumferential direction (see FIG. 6). Such a configuration has the advantage of improving steering stability performance (particularly turning performance) of the tire compared to a configuration in which the first shoulder groove 44 and the second shoulder groove 45 are inclined in the same direction.

Further, in the pneumatic tire 1, the inclination angle θ5 of the second shoulder groove 45 with respect to the tire circumferential direction is in the range of 30[deg]≦θ5≦60[deg]. Accordingly, there is an advantage that the inclination angle θ5 of the second shoulder groove 45 is optimized.

Further, in the pneumatic tire 1, the shoulder land portion 32 is provided with third shoulder grooves 46 arranged between the adjacent first shoulder grooves 44, 44 (see FIG. 6). Further, the extension length L6 of the third shoulder groove 46 in the tire contact patch and the extension length L4 of the first shoulder groove 44 have a relationship of 1.10≦L6/L4≦1.25. With such a configuration, the edge component of the shoulder land portion 32 is increased by the third shoulder groove 46, and there is an advantage that the snow performance of the tire is improved.

In addition, in the pneumatic tire 1, the center land portion 31 includes a plurality of sets of groove units 4ce, each of which includes a first center groove 41, a second center groove 42, and a third center groove 43 (see FIG. 2). reference). In addition, the first center groove 41, the second center groove 42 and the third center groove 43 are arranged without intersecting each other and arranged radially at intervals α, β and γ of 90 [deg] or more and 150 [deg] or less. (see FIG. 4). The first center groove 41 has a groove width Wg1 of 1.5 [mm] or more and 4.0 [mm] or less, and opens into the shoulder main groove 22 at one end and opens at the other end. end within the center land portion 31 .

In such a configuration, (1) the wet performance of the tire is ensured by the groove unit 4ce in which the three center grooves 41 to 43 form a set. (2) Since the center grooves 41 to 43 are arranged without crossing each other, the rigidity of the center land portion 31 is ensured, and the dry performance of the tire is ensured. (3) Since the center grooves 41 to 43 radially extend at intervals α, β, and γ of 90 [deg] or more and 150 [deg] or less, compared to a configuration in which the center grooves 41 to 43 are unevenly distributed. , the rigidity of the center land portion 31 is efficiently ensured, and the dry performance of the tire is efficiently improved. (4) Since the first center groove 41 is a lug groove, the drainage performance of the land portions 31 and 32 is ensured, and the wet performance of the tire is ensured. As a result, there is an advantage that wet performance and dry performance of the tire are compatible.

FIG. 8 is a chart showing results of performance tests of the pneumatic tire according to the embodiment of the invention. 9 and 10 are explanatory diagrams showing test tires of a conventional example (FIG. 9) and a comparative example (FIG. 10). These figures show tread plan views of the center land portion and the shoulder land portion in one side region of the tire.

In this performance test, multiple types of test tires were evaluated for (1) dry steering stability performance, (2) wet braking performance, and (3) snow steering stability performance. A test tire with a tire size of 185/60R15 was mounted on a rim with a rim size of 15×6J, and the internal pressure of the front wheel of 240 [kPa] and the rear wheel of 230 [kPa] and the maximum load specified by JATMA were applied to the test tire.

(1) In the evaluation of dry steering stability performance, the test vehicle runs on a dry road surface test course having a flat circuit at 60 [km/h] to 100 [km/h]. A test driver then conducts a sensory evaluation of steering performance during lane changes and cornering, as well as stability during straight-ahead driving. This evaluation is performed by index evaluation with the conventional example as a standard (100), and the larger the value, the better. Further, when the numerical value is 98 or more, it can be said that the dry steering stability performance is properly ensured.

(2) In the evaluation of wet braking performance, the test vehicle runs on an asphalt road sprinkled with water at a water depth of 1 [mm], and the braking distance is measured from an initial speed of 40 [km/h]. Then, based on the measurement results, index evaluation is performed with the conventional example as the standard (100). Evaluation is so preferable that the numerical value is large.

(3) In the evaluation of snow steering stability performance, the test vehicle runs on a predetermined handling course on a snowy road at a speed of 40 [km/h], and the test driver performs a sensory evaluation of steering stability. This evaluation is performed by index evaluation with the conventional example as a standard (100), and the larger the value, the better.

The test tire of the example has the configuration shown in FIGS. 32 has a circumferential narrow groove 23 and first to third shoulder grooves 44-46. Further, the width Wce of the center land portion 31 is Wce=20 [mm], and the width Wsh of the shoulder land portion 32 is Wsh=30.0 [mm]. Further, the shoulder main groove 22 has a groove width Wgm of 9.3 [mm] and a groove depth Hm of 7.0 [mm]. The groove width Wgs of the circumferential narrow groove 23 is 1.5 [mm], and the groove depth Hs is 3.5 [mm]. Further, the groove width Wg4 of the first shoulder groove 44 is 3.8 [mm], the groove depth H4 is 5.0 [mm], and the inclination angle θ4 is 86 [deg]. Further, the groove width Wg5 of the second shoulder groove 45 is 0.8 [mm], the groove depth H5 is 3.5 [mm], and the inclination angle θ5 is 54 [deg]. Further, the groove width Wg6 of the third shoulder groove 46 is 0.8 [mm], the groove depth H6 is 5.0 [mm], and the inclination angle θ6 is 86 [deg]. Also, the first shoulder groove 44 and the second shoulder groove 45 are separated from each other, and the distance Dc is 1.0 [mm].

The test tire of the conventional example has the configuration shown in FIG. 9, and differs from the test tire of Example 1 in that the circumferential narrow grooves 23 (FIG. 3) are discontinuous sipes in the tire circumferential direction. . The test tire of the comparative example has the configuration shown in FIG. 10 and differs from the test tire of Example 1 in that the circumferential narrow grooves 23 cross the first shoulder grooves 44 .

As shown in the test results, it can be seen that the test tire of the example achieves both wet performance, snow performance, and dry performance.

1 pneumatic 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 center main groove, 22 Shoulder main groove 23 Circumferential narrow groove 31 Center main groove 32 Shoulder land portion 4ce Groove unit 41 First center groove 42 Second center groove 43 Third center groove 44 First shoulder groove 45 Third Second shoulder groove, 46 Third shoulder groove

Claims (15)

A pneumatic tire comprising a center main groove and a shoulder main groove extending in the tire circumferential direction, and a center land portion and a shoulder land portion partitioned by the center main groove and the shoulder main groove,
The shoulder land portion has a circumferential narrow groove extending continuously in the tire circumferential direction, and a first groove that opens to the tire ground contact edge at one end and terminates within the shoulder land portion at the other end. a shoulder groove, and a second shoulder groove that opens into the shoulder main groove at one end and terminates in the shoulder land portion at the other end,
The first shoulder groove has a groove width of 1.5 [mm] or more and 4.0 [mm] or less and does not intersect with the circumferential fine groove,
the second shoulder groove has a groove width of 0.6 [mm] or more and 1.2 [mm] or less and intersects the circumferential narrow groove;
A pneumatic tire, wherein the second shoulder grooves are spaced apart from the first shoulder grooves in the tire width direction . The pneumatic tire according to claim 1, wherein the groove width Wgs of the circumferential narrow groove has a relationship of 0.10≤Wgs/Wgm≤0.40 with respect to the groove width Wgm of the shoulder main groove. 3. The pneumatic tire according to claim 1, wherein the groove depth Hs of the circumferential narrow grooves has a relationship of 0.30≦Hs/Hm≦0.70 with respect to the groove depth Hm of the shoulder main grooves. . A distance Ds from an edge portion of the shoulder land portion on the shoulder main groove side to a groove center line of the circumferential narrow groove is 0.10≤Ds/Wsh≤ with respect to a width Wsh of the ground contact area of the shoulder land portion. A pneumatic tire according to any one of claims 1 to 3, having a relationship of 0.40. The pneumatic tire according to any one of claims 1 to 4, wherein the shoulder land portion has no other circumferential narrow grooves in a region between the circumferential narrow grooves and the tire ground contact edge. The extension length L4 of the first shoulder groove within the contact surface of the shoulder land portion has a relationship of 0.30≦L4/Wsh≦0.50 with respect to the width Wsh of the contact area of the shoulder land portion. The pneumatic tire according to any one of claims 1-5. The pneumatic tire according to any one of claims 1 to 6, wherein the width Wsh of the ground contact area of the shoulder land portion has a relationship of 0.15≤Wsh/TW≤0.35 with respect to the tire contact width TW. . The pneumatic tire according to any one of claims 1 to 7, wherein an inclination angle θ4 of the first shoulder grooves with respect to the tire circumferential direction is in a range of 50 [deg] ≤ θ4 ≤ 88 [deg]. The air according to any one of claims 1 to 8, wherein the distance Dc between the second shoulder groove and the first shoulder groove is in the range of 1.0 [mm] ≤ Dc ≤ 5.0 [mm] entered tire. The pneumatic tire according to any one of claims 1 to 9 , wherein the first shoulder grooves and the second shoulder grooves are inclined in opposite directions with respect to the tire circumferential direction. 11. The pneumatic tire according to claim 10 , wherein an inclination angle θ5 of the second shoulder grooves with respect to the tire circumferential direction is in a range of 30[deg]≦θ5≦60[deg]. The shoulder land portion includes a third shoulder groove disposed between the adjacent first shoulder grooves, and the extension length L6 of the third shoulder groove in the tire ground contact surface is equal to the first shoulder The pneumatic tire according to any one of claims 1 to 11 , having a relationship of 1.10≤L6/L4≤1.25 with respect to the extended length L4 of the groove. The center land portion includes a plurality of sets of groove units each including a first center groove, a second center groove and a third center groove,
The first center groove, the second center groove, and the third center groove are arranged without intersecting each other and radially extend at an arrangement interval of 90 [deg] or more and 150 [deg] or less, and
The first center groove has a groove width of 1.5 [mm] or more and 4.0 [mm] or less, and opens into the shoulder main groove at one end and the center at the other end. The pneumatic tire according to any one of claims 1 to 12 , which terminates within the land portion. A pneumatic tire comprising a center main groove and a shoulder main groove extending in the tire circumferential direction, and a center land portion and a shoulder land portion partitioned by the center main groove and the shoulder main groove,
The shoulder land portion has a circumferential narrow groove extending continuously in the tire circumferential direction, and a first groove that opens to the tire ground contact edge at one end and terminates within the shoulder land portion at the other end. a shoulder groove, and a second shoulder groove that opens into the shoulder main groove at one end and terminates in the shoulder land portion at the other end,
The first shoulder groove has a groove width of 1.5 [mm] or more and 4.0 [mm] or less and does not intersect with the circumferential fine groove,
the second shoulder groove has a groove width of 0.6 [mm] or more and 1.2 [mm] or less and intersects the circumferential narrow groove;
A pneumatic tire, wherein the first shoulder groove and the second shoulder groove are inclined in opposite directions to each other with respect to the tire circumferential direction . A pneumatic tire comprising a center main groove and a shoulder main groove extending in the tire circumferential direction, and a center land portion and a shoulder land portion partitioned by the center main groove and the shoulder main groove,
The shoulder land portion has a circumferential narrow groove extending continuously in the tire circumferential direction, and a first groove that opens to the tire ground contact edge at one end and terminates within the shoulder land portion at the other end. a shoulder groove, and a second shoulder groove that opens into the shoulder main groove at one end and terminates in the shoulder land portion at the other end,
The first shoulder groove has a groove width of 1.5 [mm] or more and 4.0 [mm] or less and does not intersect with the circumferential fine groove,
the second shoulder groove has a groove width of 0.6 [mm] or more and 1.2 [mm] or less and intersects the circumferential fine groove;
The center land portion includes a plurality of sets of groove units each including a first center groove, a second center groove and a third center groove, and the first center groove, the second center groove and the third center groove. The center grooves are arranged without intersecting each other and radially extend at an arrangement interval of 90 [deg] or more and 150 [deg] or less, and
The first center groove has a groove width of 1.5 [mm] or more and 4.0 [mm] or less, and opens into the shoulder main groove at one end and the center at the other end. A pneumatic tire characterized by terminating within a land portion .

Images