JP7639368B2 - tire - Google Patents

Description

The present invention relates to tires. In particular, the present invention relates to improvements in tire tread patterns.

The tread of a typical tire has circumferential grooves and inclined grooves. The circumferential grooves drain water between the tire and the road surface primarily in the front-to-rear direction. The inclined grooves drain this water primarily in the sideways direction. These grooves contribute to the tire's wet grip performance.

JP 2018-167717 A describes a tire with three circumferential grooves. One circumferential groove is located on the front side of the equator. Two circumferential grooves are located on the back side of the equator. In other words, the tread pattern of this tire is asymmetric with respect to the equator. This tread pattern can contribute to wet grip performance and dry grip performance.

JP2018-167717A

There is room for improvement in the grip performance of conventional tires. Furthermore, there is also room for improvement in the wear resistance of conventional tires. The object of the present invention is to provide a tire that has excellent wet grip performance, dry grip performance, and wear resistance.

The tire according to the present invention has a tread having a tread surface.
(1) a first circumferential groove located on an outer side of an equatorial plane of the tire;
(2) a second circumferential groove located on the rear side of the equatorial plane;
and (3) a third circumferential groove located behind the second circumferential groove. The first circumferential groove (1) is
(1-1) a main section having a front side wall and a back side wall, and (1-2) a subsection extending from the front side wall to the tread surface and having an inclination angle θ1s larger than the inclination angle θ1f of the front side wall. The width W1m of the main section is smaller than the width W2 of the second circumferential groove and is smaller than the width W3 of the third circumferential groove.

Preferably, the ratio of the width W1m of the main section to the width Tw of the tread surface is 1.0% or more and 5.0% or less.

Preferably, the inclination angle θ1f of the front side wall is greater than or equal to 0° and less than or equal to 45°. Preferably, the inclination angle θ1s of the subsection is greater than or equal to 40° and less than or equal to 80°.

Preferably, the width W1s (mm) of the subsection satisfies the following formula:
1.0 * cosθ1f ≦ W1s ≦ 5.0 * cosθ1f

The second circumferential groove may have a front wall and a rear wall. Preferably, the ratio of the inclination angle θ2b (degrees) of the rear wall to the width Tw (mm) of the tread surface is 5% or more and 20% or less. Preferably, the ratio of the inclination angle θ2f of the front wall to the inclination angle θ2b of the rear wall is 60% or more and 90% or less.

The third circumferential groove may have a front wall and a rear wall. Preferably, the ratio of the inclination angle θ3b (degrees) of the rear wall to the width Tw (mm) of the tread surface is 5% or more and 20% or less. Preferably, the ratio of the inclination angle θ3f of the front wall to the inclination angle θ3b of the rear wall is 60% or more and 90% or less.

Preferably, the tire comprises:
(4) a front-side triangular groove extending from the second circumferential groove toward the rear side and having a circumferential size and a depth that gradually decrease toward the rear side; and (5) a rear-side triangular groove extending from the third circumferential groove toward the front side and having a circumferential size and a depth that gradually decrease toward the front side.

Preferably, the ratio of the width Wtf of the front triangular groove to the width Wr of the rib sandwiched between the second circumferential groove and the third circumferential groove is 0.10 or more and 0.30 or less. Preferably, the ratio of the width Wtb of the back triangular groove to the width Wr of the rib is 0.10 or more and 0.30 or less.

Preferably, the inclination angle θtf of the bottom of the front triangular groove is 40° or more and 70° or less. Preferably, the inclination angle θtb of the bottom of the back triangular groove is 40° or more and 70° or less.

Preferably, the tire comprises:
(6) The tire further includes a sipe connecting the front triangular groove and the rear triangular groove. Preferably, the sipe has a depth Dp of 2.0 mm or more.

In the pneumatic tire according to the present invention, multiple circumferential grooves contribute to wet grip performance. These circumferential grooves do not significantly impair the rigidity of the tread. Therefore, this tire has excellent dry grip performance. These circumferential grooves do not promote uneven wear of the tread. This tire also has excellent wear resistance.

FIG. 1 is a front view showing a tire according to an embodiment of the present invention together with a vehicle. FIG. 2 is an enlarged cross-sectional view of a portion of the tire of FIG. FIG. 3 is a development view showing a portion of the tread pattern of the tire of FIG. FIG. 4 is an enlarged cross-sectional view taken along line IV-IV in FIG. FIG. 5 is an enlarged cross-sectional view taken along line VV in FIG. FIG. 6 is an enlarged cross-sectional view taken along line VI-VI in FIG. FIG. 7 is an enlarged cross-sectional view taken along line VII-VII in FIG.

The present invention will now be described in detail based on a preferred embodiment, with reference to the drawings as appropriate.

In FIG. 1, a tire 2 is shown together with a vehicle 4. The vehicle 4 has a body 6 and an axle 8. The tire 2 is connected to the axle 8 via a wheel and a hub, neither of which are shown. The left side in FIG. 1 is the face side of the tire 2. This face side is also the outer side in the width direction of the vehicle 4. The right side in FIG. 1 is the back side of the tire 2. This back side is also the inner side in the width direction of the vehicle 4.

Figure 2 shows a portion of a cross section of tire 2 in Figure 1 taken along a plane including the axis of rotation of tire 2. In Figure 2, the vertical direction is the radial direction of tire 2, the horizontal direction is the axial direction of tire 2, and the direction perpendicular to the paper surface is the circumferential direction of tire 2. In Figure 2, dashed dotted line CL represents the equatorial plane of tire 2. With the exception of the tread pattern described below, the shape of tire 2 is mirror symmetrical with respect to the equatorial plane CL. This dashed dotted line CL is also the centerline of tire 2 in the axial direction.

The tire 2 has a tread 10, a pair of sidewalls 12, a pair of beads 14, a carcass 16, a belt 18, a band 20, and an inner liner 22. The tire 2 may have various other components. The tire 2 is of a tubeless type. The tire 2 is typically mounted on a four-wheeled vehicle.

The tread 10 has a shape that is convex radially outward. The tread 10 forms a tread surface 24 that comes into contact with the road surface. The material of the tread 10 is a cross-linked rubber composition. The tread 10 may have a base and a cap that covers the base. The tread 10 may have three or more layers. The tread 10 has a plurality of grooves 34, 36, 38. These grooves 34, 36, 38 form a tread pattern. The configuration of the tread pattern will be described in detail later.

Each sidewall 12 extends radially inward from the tread 10. A portion of the sidewall 12 is joined to the tread 10. The sidewall 12 is made of crosslinked rubber that has excellent cut resistance and weather resistance. The sidewall 12 prevents damage to the carcass 16.

Each bead 14 is located axially inward of the sidewall 12. The bead 14 has a core 26 and an apex 28 extending radially outward from the core 26. The core 26 is ring-shaped and includes a wound inelastic wire. The wire is typically made of steel. The apex 28 tapers radially outward. The apex 28 is made of high-hardness crosslinked rubber.

The carcass 16 is laid between the beads 14 on both sides and is aligned with the tread 10 and the sidewall 12. The carcass 16 has a large number of parallel cords and topping rubber. The absolute value of the angle that each cord makes with respect to the equatorial plane CL is 75° to 90°. In other words, the carcass 16 has a radial structure. The cords are made of organic fibers. Examples of preferred organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

The belt 18 is located radially inside the tread 10. The belt 18 is laminated with the carcass 16. The belt 18 reinforces the carcass 16. The belt 18 has an inner layer 30 and an outer layer 32. Each of the inner layer 30 and the outer layer 32 has a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equatorial plane CL. The general absolute value of the inclination angle is 10° or more and 35° or less. The inclination direction of the cord of the inner layer 30 with respect to the equatorial plane CL is opposite to the inclination direction of the cord of the outer layer 32 with respect to the equatorial plane CL. The preferred material of the cord is steel. Organic fibers may be used for the cord. Examples of organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

The band 20 is located radially outward of the belt 18. The band 20 has a cord and a topping rubber. The cord is wound in a spiral shape. The band 20 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is 5° or less, and further 2° or less. The cord is made of organic fibers. Examples of preferred organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

3 is a development view showing a part of the tread pattern of the tire 2 in FIG. 1. In FIG. 3, the up-down direction is the circumferential direction. The up-down direction is also the traveling direction (i.e., the front side) of the tire 2. In FIG. 3, the left side is the front side and the right side is the back side. This tread pattern has a first circumferential groove 34, a second circumferential groove 36, and a third circumferential groove 38. These circumferential grooves divide the tread surface 24 into four ribs. Specifically, the tread surface 24 has a first rib 40, a second rib 42, a third rib 44, and a fourth rib 46. The first rib 40 is located on the front side of the first circumferential groove 34. The second rib 42 is sandwiched between the first circumferential groove 34 and the second circumferential groove 36. The third rib 44 is sandwiched between the second circumferential groove 36 and the third circumferential groove 38. The fourth rib 46 is located on the back side of the third circumferential groove 38. In FIG. 3, the symbol Tw represents the width of the tread 10, and the symbol Wr represents the width of the third rib 44. The widths Tw and Wr are measured along the axial direction.

This tread pattern has a plurality of first lateral grooves 48 each located on the front side of the first circumferential groove 34. This tread pattern has a plurality of second lateral grooves 50 each extending from the first circumferential groove 34 toward the front side, and a plurality of third lateral grooves 52 each extending from the first circumferential groove 34 toward the back side. This tread pattern has a plurality of fourth lateral grooves 54 each extending from the second circumferential groove 36 toward the front side. This tread pattern has a plurality of fifth lateral grooves 56 each extending from the third circumferential groove 38 toward the back side. This tread pattern has a plurality of sixth lateral grooves 58 each located on the back side of the third circumferential groove 38.

In this tread pattern, the pattern of units 60 shown in FIG. 3 is repeated circumferentially. Thus, the pitch of the lateral grooves is constant. The tread pattern may have variations in the pitch of the lateral grooves.

The first circumferential groove 34 extends in the circumferential direction. Therefore, the first circumferential groove 34 is annular. The first circumferential groove 34 is located on the front side of the equatorial plane CL. In this tread pattern, the number of circumferential grooves located on the front side of the equatorial plane CL is 1.

Figure 4 is an enlarged cross-sectional view taken along line IV-IV in Figure 3. Figure 4 shows the vicinity of the first circumferential groove 34. The up-down direction in Figure 4 is the normal direction to the tread surface 24. In Figure 4, the left side is the front side, and the right side is the back side. This first circumferential groove 34 has a main section 62 and a subsection 64. In Figure 4, reference numeral 66 indicates the boundary between the main section 62 and the subsection 64. The subsection 64 is located on the front side of the main section 62 (the left side in Figure 4). The main section 62 has a bottom surface 68, a front side wall 70, and a back side wall 72.

The front side wall 70 is located on the front side of the bottom surface 68. The front side wall 70 stands up from the bottom surface 68. The front side wall 70 is inclined with respect to the normal direction. The direction of this inclination is a direction toward the front side as it moves away from the bottom surface 68. In FIG. 4, the symbol θ1f represents the inclination angle (degree) of the front side wall 70 with respect to the normal direction.

The rear wall 72 is located on the rear side of the bottom surface 68. The rear wall 72 stands up from the bottom surface 68. The rear wall 72 is inclined with respect to the normal direction. The direction of this inclination is a direction toward the rear side as it moves away from the bottom surface 68. In FIG. 4, the symbol θ1b indicates the inclination angle (degree) of the rear wall 72 with respect to the normal direction. In this embodiment, the inclination angle θ1b is the same as the inclination angle θ1f. The first circumferential groove 34 may have a main section 62 in which the inclination angle θ1b is different from the inclination angle θ1f.

In FIG. 4, the symbol W1m represents the width (mm) of the main section 62. The width W1m is the distance between the normal to the boundary 66 and the normal to the edge 74 of the rear wall 72.

The subsection 64 extends from the front sidewall 70 to the tread surface 24. The subsection 64 is inclined with respect to the normal direction. The direction of this inclination is toward the front side as it moves away from the boundary 66. In FIG. 4, the symbol θ1s represents the inclination angle (degree) of the subsection 64 with respect to the normal direction. The inclination angle θ1s is greater than the inclination angle θ1f of the front sidewall 70.

In FIG. 4, the symbol W1s represents the width (mm) of the subsection 64. The width W1s is the distance between the normal to the boundary 66 and the normal to the edge 76 of the subsection 64.

As shown in FIG. 3, the second circumferential groove 36 extends along the circumferential direction. Therefore, the second circumferential groove 36 is annular. The second circumferential groove 36 is located behind the equatorial plane CL. In this embodiment, the second circumferential groove 36 is separated from the equatorial plane CL. The second circumferential groove 36 may straddle the equatorial plane CL. In this case, the axial center of the second circumferential groove 36 is located behind the equatorial plane CL. In other words, in the present invention, the axial center of the groove is used as a reference to determine the zone to which the groove belongs.

Figure 5 is an enlarged cross-sectional view taken along line V-V in Figure 3. Figure 5 shows the vicinity of the second circumferential groove 36. The up-down direction in Figure 5 is the normal direction to the tread surface 24. In Figure 5, the left side is the front side, and the right side is the back side. This second circumferential groove 36 has a bottom surface 78, a front side wall 80, and a back side wall 82.

The front side wall 80 is located on the front side of the bottom surface 78. The front side wall 80 stands up from the bottom surface 78. The front side wall 80 is inclined with respect to the normal direction. The direction of this inclination is a direction toward the front side as it moves away from the bottom surface 78. In FIG. 5, the symbol θ2f represents the inclination angle (degree) of the front side wall 80 with respect to the normal direction.

The rear wall 82 is located on the rear side of the bottom surface 78. The rear wall 82 stands up from the bottom surface 78. The rear wall 82 is inclined with respect to the normal direction. The direction of this inclination is a direction toward the rear side as it moves away from the bottom surface 78. In FIG. 5, the symbol θ2b represents the inclination angle (degree) of the rear wall 82 with respect to the normal direction. In this embodiment, the inclination angle θ2b is larger than the inclination angle θ2f. The tire 2 may have a second circumferential groove 36 in which the inclination angle θ2b is the same as the inclination angle θ2f. The tire 2 may have a second circumferential groove 36 in which the inclination angle θ2b is smaller than the inclination angle θ2f.

In FIG. 5, the symbol W2 indicates the width (mm) of the second circumferential groove 36. The width W2 is the distance between the normal line at the edge 84 of the front side wall 80 and the normal line at the edge 86 of the rear side wall 82.

As shown in FIG. 3, the third circumferential groove 38 extends in the circumferential direction. Therefore, the second circumferential groove 36 is annular. The third circumferential groove 38 is located behind the equatorial plane CL. The third circumferential groove 38 is located behind the second circumferential groove 36. In this tread pattern, the number of circumferential grooves located behind the equatorial plane CL is two.

Figure 6 is an enlarged cross-sectional view taken along line VI-VI in Figure 3. Figure 6 shows the vicinity of the third circumferential groove 38. The up-down direction in Figure 6 is the normal direction to the tread surface 24. In Figure 6, the left side is the front side, and the right side is the back side. This third circumferential groove 38 has a bottom surface 88, a front side wall 90, and a back side wall 92.

The front side wall 90 is located on the front side of the bottom surface 88. The front side wall 90 stands up from the bottom surface 88. The front side wall 90 is inclined with respect to the normal direction. The direction of this inclination is a direction toward the front side as it moves away from the bottom surface 88. In FIG. 6, the symbol θ3f represents the inclination angle (degree) of the front side wall 90 with respect to the normal direction.

The rear wall 92 is located on the rear side of the bottom surface 88. The rear wall 92 stands up from the bottom surface 88. The rear wall 92 is inclined with respect to the normal direction. The direction of this inclination is a direction toward the rear side as it moves away from the bottom surface 88. In FIG. 6, the symbol θ3b indicates the inclination angle (degree) of the rear wall 92 with respect to the normal direction. In this embodiment, the inclination angle θ3b is larger than the inclination angle θ3f. The tire 2 may have a third circumferential groove 38 whose inclination angle θ3b is the same as the inclination angle θ3f. The tire 2 may have a third circumferential groove 38 whose inclination angle θ3b is smaller than the inclination angle θ3f.

In FIG. 6, the symbol W3 indicates the width (mm) of the third circumferential groove 38. The width W3 is the distance between the normal line at the edge 94 of the front side wall 90 and the normal line at the edge 96 of the rear side wall 92.

As shown in FIG. 3, this tread pattern has a plurality of front triangular grooves 98, a plurality of rear triangular grooves 100, and a plurality of sipes 102. These front triangular grooves 98, rear triangular grooves 100, and sipes 102 are located on the rear side of the equatorial plane CL.

Each of the front triangular grooves 98 is continuous with the second circumferential groove 36. The front triangular grooves 98 extend from the second circumferential groove 36 toward the rear side. The front triangular grooves 98 have a circumferential size that gradually decreases toward the rear side. The contour of the front triangular groove 98 as viewed from the normal direction of the tread surface 24 is generally triangular. In FIG. 3, the symbol Wtf represents the width (mm) of the front triangular groove 98. The width Wtf is measured along a direction perpendicular to the normal line of the tread surface 24.

Each of the rear triangular grooves 100 is continuous with the third circumferential groove 38. The rear triangular grooves 100 extend from the third circumferential groove 38 toward the front side. The rear triangular grooves 100 have a circumferential size that gradually decreases toward the front side. The contour of the rear triangular groove 100 as viewed from the normal direction of the tread surface 24 is generally triangular. In this embodiment, the contour shape of the rear triangular groove 100 is congruent with the contour shape of the front triangular groove 98. In this embodiment, the number of the rear triangular grooves 100 is the same as the number of the front triangular grooves 98. In FIG. 3, the symbol Wtb represents the width (mm) of the rear triangular groove 100. The width Wtb is measured along a direction perpendicular to the normal to the tread surface 24.

Each sipe 102 connects a front triangular groove 98 and a rear triangular groove 100. The sipes 102 form a pair of a front triangular groove 98 and a rear triangular groove 100. In this embodiment, the sipes 102 are inclined with respect to the axial direction. Specifically, the sipes 102 extend in a direction toward the front as they approach the rear side. In this embodiment, the number of sipes 102 matches the number of front triangular grooves 98 and also matches the number of rear triangular grooves 100. The third rib 44 is divided into a plurality of elements 104 by the plurality of sipes 102.

Figure 7 is an enlarged cross-sectional view taken along line VII-VII in Figure 3. The direction of line VII-VII generally coincides with the extension direction of the sipes 102. Figure 7 shows the second circumferential groove 36, the front triangular groove 98, the sipes 102, the rear triangular groove 100, and the third circumferential groove 38.

The bottom 104 of the front triangular groove 98 is inclined with respect to the normal direction. This bottom 104 extends in a direction toward the tread surface 24 toward the back side. In other words, the front triangular groove 98 has a depth that gradually decreases toward the back side. In FIG. 7, the symbol θtf represents the inclination angle (degree) of the bottom 104 of the front triangular groove 98 with respect to the normal direction.

The bottom 106 of the rear triangular groove 100 is inclined with respect to the normal direction. This bottom 106 extends in a direction toward the tread surface 24 as it approaches the front side. In other words, the rear triangular groove 100 has a depth that gradually decreases as it approaches the front side. In FIG. 7, the symbol θtb represents the inclination angle (degree) of the bottom 106 of the rear triangular groove 100 with respect to the normal direction. In this embodiment, the inclination angle θtb is the same as the inclination angle θtf. The tire 2 may have a tread 10 in which the inclination angle θtb is different from the inclination angle θtf.

In FIG. 7, the symbol Dp represents the depth (mm) of the sipe 102. This depth is small. Furthermore, as is clear from FIG. 3, the width of the sipe 102 is extremely small. Therefore, the distance between one tread rubber and the other tread rubber facing each other across the sipe 102 is extremely small. One tread rubber may abut against the other tread rubber. Since the sipe 102 has a small depth Dp and a small width, the sipe 102 does not significantly impair the rigidity of the third rib 44.

The tire 2 may have a tread pattern that does not include the sipes 102. The tire 2 may have a tread pattern that does not include the front triangular groove 98 and the rear triangular groove 100.

In this tread surface 24, the width W1m (see FIG. 4) of the main section 62 is smaller than the width W2 (see FIG. 5) of the second circumferential groove 36 and smaller than the width W3 (see FIG. 6) of the third circumferential groove 38. On the back side of the tread surface 24 relative to the equatorial plane CL, there are two circumferential grooves with larger widths. When the tire 2 runs on a wet road surface, water between the road surface and the tread surface 24 is efficiently discharged by the second circumferential groove 36 and the third circumferential groove 38. The second circumferential groove 36 and the third circumferential groove 38 can contribute to the wet grip performance of the tire 2.

The number of circumferential grooves present on the outer side of the equatorial plane CL of the tread surface 24 is only one. Moreover, the width W1m of the main section 62 of this circumferential groove is small. Furthermore, the subsection 64 is shallow. Therefore, the rigidity of the tread 10 on the outer side of the equatorial plane CL is high. When the vehicle 4 turns, a large ground pressure is applied to the portion of the tread 10 on the outer side of the equatorial plane CL. Even when this ground pressure is applied, the tread 10 does not deform excessively. This tire 2 has excellent dry grip performance and wear resistance.

The first circumferential groove 34 has a subsection 64, which prevents rubber from entering the main section 62 due to elastic deformation of the first rib 40. Therefore, the cross-sectional area of the main section 62 when ground pressure is applied is sufficiently large. In this tire 2, the drainage of the main section 62 is not impaired even when ground pressure is applied. This tire 2 has extremely excellent wet grip performance.

The subsection 64 prevents rubber from entering the main section 62, so uneven wear of the rubber caused by this intrusion does not occur. This tire 2 has excellent wear resistance.

The tire 2 according to the present invention has excellent wet grip performance, dry grip performance, and wear resistance. This tire 2 is suitable for driving on circuits and on public roads. This tire 2 is particularly suitable for driving on circuits.

3, L1 represents the distance from the equatorial plane CL to the axial center of the first circumferential groove 34, L2 represents the distance from the equatorial plane CL to the axial center of the second circumferential groove 36, and L3 represents the distance from the equatorial plane CL to the axial center of the third circumferential groove 38. These distances L1, L2, and L3 are measured along the axial direction. A tire 2 in which these distances L1, L2, and L3 are appropriate has excellent performance. The ratio of the distance L1 to the half width (Tw/2) of the tread 10 is preferably 25% or more and 60% or less. The ratio of the distance L2 to the half width (Tw/2) of the tread 10 is preferably 5% or more and 25% or less. The ratio of the distance L3 to the half width (Tw/2) of the tread 10 is preferably 35% or more and 65% or less.

A water film is likely to form between the rib and the road surface. The front triangular groove 98 guides the water between the third rib 44 and the road surface to the second circumferential groove 36. This front triangular groove 98 suppresses the formation of a water film. As described above, the front triangular groove 98 has a circumferential size that gradually decreases toward the back side. Therefore, this front triangular groove 98 does not significantly impair the rigidity of the third rib 44. As is clear from Figures 3 and 7, the cross-sectional area of the front triangular groove 98 along the circumferential direction gradually increases toward the front side. Therefore, this front triangular groove 98 smoothly guides water to the second circumferential groove 36.

The rear triangular groove 100 guides water between the third rib 44 and the road surface to the third circumferential groove 38. This rear triangular groove 100 suppresses the generation of a water film. As described above, the rear triangular groove 100 has a circumferential size that gradually decreases toward the front side. Therefore, this rear triangular groove 100 does not significantly impair the rigidity of the third rib 44. As is clear from Figures 3 and 7, the cross-sectional area of the rear triangular groove 100 along the circumferential direction gradually increases toward the rear side. Therefore, this rear triangular groove 100 smoothly guides water to the third circumferential groove 38.

The sipes 102 guide water between the third rib 44 and the road surface to the front triangular groove 98 or the rear triangular groove 100. The sipes 102 contribute to wet grip performance. The sipes 102 moderately reduce the rigidity of the third rib 44. Therefore, the sipes 102 can contribute to grip performance on road surfaces with a low coefficient of friction.

The ratio of the width W1m of the main section 62 (see FIG. 4) to the width Tw of the tread surface 24 is preferably 1.0% or more and 5.0% or less. The first circumferential groove 34 with this ratio of 1.0% or more has excellent drainage performance. From this viewpoint, this ratio is more preferably 1.5% or more, and particularly preferably 2.0% or more. The first circumferential groove 34 with this ratio of 5.0% or less does not significantly impair the rigidity of the tread 10. From this viewpoint, this ratio is more preferably 4.5% or less, and particularly preferably 4.0% or less. The width Tw of the tread surface 24 correlates with the displacement of the engine of the vehicle 4, and this displacement correlates with the force applied to the tire 2 when turning. In other words, the width Tw of the tread surface 24 correlates with the force applied to the tire 2 when turning. From this viewpoint, the present invention specifies the ratio of the width and inclination angle of each groove to the width Tw of the tread surface 24.

The width W1m is preferably 2.5 mm or more, more preferably 3.5 mm or more, and particularly preferably 4.5 mm or more. The width W1m is preferably 13.0 mm or less, more preferably 12.0 mm or less, and particularly preferably 11.5 mm or less.

The inclination angle θ1f of the front side wall 70 of the first circumferential groove 34 is preferably 45° or less. In a tread 10 with an inclination angle θ1f of 45° or less, both drainage performance and rigidity can be achieved. From this viewpoint, the inclination angle θ1f is more preferably 35° or less, and particularly preferably 30° or less. From the viewpoint of ease of manufacturing the tire 2, the inclination angle θ1f is preferably 0° or more.

The inclination angle θ1b of the back wall 72 of the first circumferential groove 34 is preferably 45° or less. In a tread 10 with an inclination angle θ1b of 45° or less, both drainage performance and rigidity can be achieved. From this viewpoint, the inclination angle θ1b is more preferably 35° or less, and particularly preferably 30° or less. From the viewpoint of ease of manufacturing the tire 2, the inclination angle θ1b is preferably 0° or more.

The inclination angle θ1s of the subsection 64 is preferably 40° or more and 80° or less. Subsections 64 with an inclination angle θ1s within this range can contribute to drainage, rigidity, and wear resistance. The inclination angle θ1s is more preferably 45° or more, and particularly preferably 50° or more. The inclination angle θ1s is more preferably 75° or less, and particularly preferably 70° or less.

The width W1s of the subsection 64 is preferably 0.5 mm or more and 3.0 mm or less. Subsections 64 with a width W1s within this range can contribute to drainage, rigidity, and abrasion resistance. From this perspective, the width W1s is more preferably 0.6 mm or more, and particularly preferably 0.7 mm or more. The width W1s is more preferably 2.0 mm or less, and particularly preferably 1.5 mm or less.

The difference (θ1s-θ1f) between the inclination angle θ1s of the subsection 64 and the inclination angle θ1f of the front sidewall 70 of the main section 62 is preferably 10° or more and 55° or less. A tire 2 whose difference (θ1s-θ1f) is within this range has excellent drainage properties, rigidity, and wear resistance. The difference (θ1s-θ1f) is more preferably 15° or more, and particularly preferably 20° or more. The difference (θ1s-θ1f) is more preferably 50° or less, and particularly preferably 45° or less.

The width W1s of the subsection 64 preferably satisfies the following formula:
1.0 * cosθ1f ≦ W1s ≦ 5.0 * cosθ1f
In other words, the ratio of the width W1s (mm) to cos θ1f is 1.0 or more and 5.0 or less. The tire 2 satisfying this formula is excellent in wet grip performance and dry grip performance. This ratio is more preferably 1.5 or more, and particularly preferably 2.0 or more. This ratio is more preferably 4.5 or less, and particularly preferably 4.0 or less.

The width W2 (see FIG. 5) of the second circumferential groove 36 is preferably 10 mm or more and 20 mm or less. A second circumferential groove 36 with a width W2 of 10 mm or more contributes to drainage. From this viewpoint, the width W2 is more preferably 12 mm or more, and particularly preferably 13 mm or more. A second circumferential groove 36 with a width W2 of 20 mm or less does not significantly impair the rigidity of the tread 10. From this viewpoint, the width W2 is more preferably 18 mm or less, and particularly preferably 17 mm or less.

The ratio (W2/W1m) of the width W2 of the second circumferential groove 36 to the width W1m of the main section 62 is preferably 1.5 or more and 2.5 or less. A tire 2 having a ratio (W2/W1m) within this range has excellent wet grip performance and dry grip performance. This ratio (W2/W1m) is more preferably 1.7 or more, and particularly preferably 1.8 or more. This ratio (W2/W1m) is more preferably 2.3 or less, and particularly preferably 2.2 or less.

The ratio of the inclination angle θ2b (degrees) of the rear wall 82 of the second circumferential groove 36 to the width Tw (mm) of the tread surface 24 is preferably 5% or more. When the vehicle 4 turns, a large lateral force is applied to the tire 2. The direction of this lateral force is from the front side to the back side. In the tread 10 with a ratio of 5% or more, the rigidity against the lateral force is large. This tire 2 has excellent dry grip performance. From this viewpoint, this ratio is more preferably 10% or more, and particularly preferably 13% or more. This ratio is preferably 20% or less. The inclination angle θ2b is preferably 13° or more, more preferably 25° or more, and particularly preferably 33° or more. The inclination angle θ2b is preferably 50° or less.

In the second circumferential groove 36, the ratio of the inclination angle θ2f of the front side wall 80 to the inclination angle θ2b of the back side wall 82 is preferably 90% or less. The cross-sectional area of the second circumferential groove 36 where this ratio is 90% or less is sufficiently large. This second circumferential groove 36 can contribute to wet grip performance. From this viewpoint, this ratio is more preferably 85% or less, and particularly preferably 80% or less. This ratio is preferably 60% or more. The inclination angle θ2f is preferably 5° or more, more preferably 15° or more, and particularly preferably 20° or more. The inclination angle θ2f is preferably 45° or less.

The width W3 (see FIG. 6) of the third circumferential groove 38 is preferably 10 mm or more and 20 mm or less. A third circumferential groove 38 with a width W3 of 10 mm or more contributes to drainage. From this viewpoint, the width W3 is more preferably 12 mm or more, and particularly preferably 13 mm or more. A third circumferential groove 38 with a width W3 of 20 mm or less does not significantly impair the rigidity of the tread 10. From this viewpoint, the width W3 is more preferably 18 mm or less, and particularly preferably 17 mm or less.

The ratio (W3/W1m) of the width W3 of the third circumferential groove 38 to the width W1m of the main section 62 is preferably 1.5 or more and 2.5 or less. A tire 2 having a ratio (W3/W1m) within this range has excellent wet grip performance and dry grip performance. This ratio (W3/W1m) is more preferably 1.7 or more, and particularly preferably 1.8 or more. This ratio (W3/W1m) is more preferably 2.3 or less, and particularly preferably 2.2 or less.

The ratio of the inclination angle θ3b (degrees) of the rear wall 92 of the third circumferential groove 38 to the width Tw (mm) of the tread surface 24 is preferably 5% or more. When the vehicle 4 turns, a large lateral force is applied to the tire 2. The direction of this lateral force is from the front side to the back side. In the tread 10 with a ratio of 5% or more, the rigidity against the lateral force is large. This tire 2 has excellent dry grip performance. From this viewpoint, this ratio is more preferably 10% or more, and particularly preferably 13% or more. This ratio is preferably 20% or less. The inclination angle θ3b is preferably 13° or more, more preferably 25° or more, and particularly preferably 33° or more. The inclination angle θ3b is preferably 50° or less.

In the third circumferential groove 38, the ratio of the inclination angle θ3f of the front side wall 90 to the inclination angle θ3b of the back side wall 92 is preferably 90% or less. The cross-sectional area of the third circumferential groove 38 where this ratio is 90% or less is sufficiently large. This third circumferential groove 38 can contribute to wet grip performance. From this viewpoint, this ratio is more preferably 85% or less, and particularly preferably 80% or less. This ratio is preferably 60% or more. The inclination angle θ3f is preferably 5° or more, more preferably 15° or more, and particularly preferably 20° or more. The inclination angle θ3f is preferably 45° or less.

The ratio (Wtf/Wr) of the width Wtf (see FIG. 3) of the front triangular groove 98 to the width Wr of the third rib 44 is preferably 0.10 or more and 0.30 or less. The front triangular groove 98 with a ratio (Wtf/Wr) of 0.10 or more can contribute to drainage. From this viewpoint, the ratio (Wtf/Wr) is more preferably 0.12 or more, and particularly preferably 0.13 or more. The front triangular groove 98 with a ratio (Wtf/Wr) of 0.30 or less does not significantly impair the rigidity of the third rib 44. From this viewpoint, the ratio (Wtf/Wr) is more preferably 0.25 or less, and particularly preferably 0.22 or less. The width Wtf is preferably 3.0 mm or more, more preferably 5.0 mm or more, and particularly preferably 6.0 mm or more. The width Wtf is preferably 15.0 mm or less, more preferably 12.0 mm or less, and particularly preferably 10.0 mm or less.

The inclination angle θtf (see FIG. 7) of the bottom of the front triangular groove 98 is preferably 40° or more and 70° or less. A front triangular groove 98 with an inclination angle θtf of 40° or more can contribute to drainage. From this viewpoint, the inclination angle θtf is more preferably 45° or more, and particularly preferably 48° or more. A front triangular groove 98 with an inclination angle θtf of 70° or less does not significantly impair the rigidity of the third rib 44. From this viewpoint, the inclination angle θtf is more preferably 60° or less, and particularly preferably 55° or more.

The ratio (Wtb/Wr) of the width Wtb (see FIG. 3) of the rear triangular groove 100 to the width Wr of the third rib 44 is preferably 0.10 or more and 0.30 or less. The rear triangular groove 100 with a ratio (Wtb/Wr) of 0.10 or more can contribute to drainage. From this viewpoint, the ratio (Wtb/Wr) is more preferably 0.12 or more, and particularly preferably 0.13 or more. The rear triangular groove 100 with a ratio (Wtb/Wr) of 0.30 or less does not significantly impair the rigidity of the third rib 44. From this viewpoint, the ratio (Wtb/Wr) is more preferably 0.25 or less, and particularly preferably 0.22 or less. The width Wtb is preferably 3.0 mm or more, more preferably 5.0 mm or more, and particularly preferably 6.0 mm or more. The width Wtf is preferably 15.0 mm or less, more preferably 12.0 mm or less, and particularly preferably 10.0 mm or less.

The inclination angle θtb (see FIG. 7) of the bottom of the rear triangular groove 100 is preferably 40° or more and 70° or less. A rear triangular groove 100 with an inclination angle θtb of 40° or more can contribute to drainage. From this viewpoint, the inclination angle θtb is more preferably 45° or more, and particularly preferably 48° or more. A rear triangular groove 100 with an inclination angle θtb of 70° or less does not significantly impair the rigidity of the third rib 44. From this viewpoint, the inclination angle θtb is more preferably 60° or less, and particularly preferably 55° or more.

The depth Dp of the sipe 102 (see FIG. 7) is preferably 2.0 mm or more. The sipe 102 can contribute to drainage. From this viewpoint, the depth is more preferably 2.5 mm or more, and particularly preferably 2.8 mm or more. From the viewpoint of the rigidity of the third rib 44, the depth Dp is preferably 5.0 mm or less.

The groove area ratio Ps is preferably 10% or more and 30% or less. A tread pattern with an area ratio Ps of 10% or more has excellent drainage. From this viewpoint, the area ratio Ps is more preferably 13% or more, and particularly preferably 15% or more. A tread 10 with an area ratio Ps of 30% or less has excellent rigidity. From this viewpoint, the area ratio Ps is more preferably 25% or less, and particularly preferably 22% or less. The area ratio Ps is the ratio of the total area of all grooves in the development diagram (e.g., FIG. 3) to the virtual area of the tread surface 24. The virtual area is the area of the tread surface 24 when it is assumed that no grooves exist at all.

In the present invention, the dimensions and angles of each component of the tire 2 are measured when the tire 2 is mounted on a standard rim and filled with air to achieve the standard internal pressure. No load is applied to the tire 2 during measurement. In this specification, the standard rim means the rim specified in the standard on which the tire 2 is based. The "standard rim" in the JATMA standard, the "design rim" in the TRA standard, and the "measuring rim" in the ETRTO standard are standard rims. In this specification, the standard internal pressure means the internal pressure specified in the standard on which the tire 2 is based. The "maximum air pressure" in the JATMA standard, the "maximum value" listed in the "TIRE LOAD LIMITSAT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are standard internal pressures.

The effects of the present invention will be explained below by way of examples, but the present invention should not be interpreted in a restrictive manner based on the description of these examples.

[Example 1]
A pneumatic tire shown in Figures 1-7 was manufactured. The size of the tire was 255/40R18. The details of the tread pattern of the tire are shown in Table 1 below. In this tire, the width Tw of the tread surface was 254 mm, and the width Wr of the third rib was 40 mm.

[Example 2-4]
Tires of Examples 2 to 4 were obtained in the same manner as in Example 1, except that the specifications of the subsection of the first circumferential groove were as shown in Table 1 below.

[Examples 5 to 9]
Tires of Examples 5 to 9 were obtained in the same manner as in Example 1, except that the specifications of the main section of the first circumferential groove were as shown in Table 2 below.

[Examples 10 to 13]
Tires of Examples 10 to 13 were obtained in the same manner as in Example 1, except that the specifications of the second circumferential groove and the third circumferential groove were as shown in Table 3 below.

[Examples 14 to 21]
Tires of Examples 14 to 21 were obtained in the same manner as in Example 1, except that the specifications of the front triangular grooves and the rear triangular grooves were as shown in Tables 4 and 5 below.

[Examples 22 and 23]
Tires of Examples 22 and 23 were obtained in the same manner as in Example 1, except that the sipe specifications were as shown in Table 6 below.

[Example 24]
A tire of Example 24 was obtained in the same manner as in Example 1, except that no sipes were provided.

[Example 25]
A tire of Example 25 was obtained in the same manner as Example 1, except that the front triangular groove, the rear triangular groove and the sipes were not provided.

[Comparative Example 1]
A tire of Comparative Example 1 was obtained in the same manner as in Example 1, except that a first circumferential groove having no subsection was provided.

[Comparative Example 2]
A tire of Comparative Example 2 was obtained in the same manner as in Example 1, except that a first circumferential groove having no subsection was provided and the main session specifications were as shown in Table 7 below.

[Comparative Example 3]
A tire of Comparative Example 3 was obtained in the same manner as in Example 1, except that the first circumferential groove was not provided.

[Comparative Example 4]
A tire of Comparative Example 4 was obtained in the same manner as in Example 1, except that the specifications of the first circumferential groove, the second circumferential groove, and the third circumferential groove were as shown in Table 7 below.

[Drainage performance]
The tire was mounted on a rim with a size of "18 x 8.5J". The tire was filled with air so that the internal pressure was 220 kPa. The rim was mounted on a four-wheel drive vehicle with an engine displacement of 2000 cc. The vehicle was turned on a road surface having a puddle with a depth of 5 mm, and the lateral force was measured. The results are shown in Tables 1-7 below, with Comparative Example 2 being assigned an index of 100. Tires with a higher index have better drainage performance.

[Wet grip performance]
In the above-mentioned drainage performance test, the driver was asked to evaluate the grip performance. The results are shown in Tables 1-7 below as an index, with Comparative Example 2 being given an index of 100. Tires with a higher index value have better wet grip performance.

[Handling stability]
During the above-mentioned drainage performance test, the driver was asked to evaluate the driving stability. The results are shown in Tables 1-7 below as an index, with Comparative Example 2 being given an index of 100. Tires with a higher index value have better driving stability.

[Dry grip performance]
The vehicle was driven on a circuit course on a dry road surface, and the driver was asked to evaluate the grip performance. The results are shown in Tables 1-7 below, with Comparative Example 2 being assigned an index of 100. Tires with a higher index value have better dry grip performance.

[Wear resistance]
The vehicle was run on a circuit course with a dry road surface. When the running distance reached 20 km, the tread surface was visually observed and the degree of uneven wear was evaluated. The results are shown in Table 1-7 below as an index, with Comparative Example 2 being assigned an index of 100. Tires with a higher index value have better wear resistance.

As shown in Table 1-7, the total score for the tires of each example is high. From these evaluation results, the superiority of the present invention is clear.

The tire of the present invention can be mounted on various vehicles.

2: Tire 4: Vehicle 6: Body 8: Axle 10: Tread 24: Tread surface 34: First circumferential groove 36: Second circumferential groove 38: Third circumferential groove 40: First rib 42: Second rib 44: Third rib 46: Fourth rib 62: Main section 64: Subsection 68: Bottom surface of first circumferential groove 70: Front side wall of first circumferential groove 72: Back side wall of first circumferential groove 78: Bottom surface of second circumferential groove 80: Front side wall of second circumferential groove 82: Back side wall of second circumferential groove 88: Bottom surface of third circumferential groove 90: Front side wall of third circumferential groove 92: Back side wall of third circumferential groove 98: Front triangular groove 100: Back triangular groove 102: Sipe

Claims (10)

A tire having a tread having a tread surface,
The above tread is
(1) a first circumferential groove located on an outer side of an equatorial plane of the tire;
(2) a second circumferential groove located on the rear side of the equatorial plane;
and (3) a third circumferential groove located behind the second circumferential groove,
The first circumferential groove (1)
(1-1) a main section having a front side wall and a back side wall, and (1-2) a subsection extending from the front side wall to the tread surface, the subsection having an inclination angle θ1s greater than the inclination angle θ1f of the front side wall,
The width W1m of the main section is smaller than the width W2 of the second circumferential groove and smaller than the width W3 of the third circumferential groove,
A tire in which the width W1s (mm) of the subsection satisfies the following formula :
1.0 * cosθ1f ≦ W1s ≦ 5.0 * cosθ1f The tire according to claim 1, wherein the ratio of the width W1m of the main section to the width Tw of the tread surface is 1.0% or more and 5.0% or less. The tire according to claim 1 or 2, wherein the inclination angle θ1f of the front side wall is 0° or more and 45° or less. A tire according to any one of claims 1 to 3, wherein the inclination angle θ1s of the subsection is 40° or more and 80° or less. The second circumferential groove has a front side wall and a back side wall,
a ratio of the inclination angle θ2b (degree) of the rear side wall to the width Tw (mm) of the tread surface is 5% or more and 20% or less,
The tire according to claim 1 , wherein a ratio of the inclination angle θ2f of the front side wall to the inclination angle θ2b of the rear side wall is equal to or greater than 60% and is equal to or less than 90%. the third circumferential groove has a front side wall and a back side wall,
a ratio of the inclination angle θ3b (degree) of the rear side wall to the width Tw (mm) of the tread surface is 5% or more and 20% or less,
The tire according to claim 1 , wherein a ratio of the inclination angle θ3f of the front side wall to the inclination angle θ3b of the rear side wall is equal to or greater than 60% and is equal to or less than 90%. A tire having a tread having a tread surface,
The above tread is
(1) a first circumferential groove located on an outer side of an equatorial plane of the tire;
(2) a second circumferential groove located on the rear side of the equatorial plane;
and
(3) a third circumferential groove located behind the second circumferential groove
It has
The first circumferential groove (1)
(1-1) Main section having front and back walls
and
(1-2) A subsection extending from the front side wall to the tread surface, the subsection having an inclination angle θ1s greater than the inclination angle θ1f of the front side wall.
It has
The width W1m of the main section is smaller than the width W2 of the second circumferential groove and smaller than the width W3 of the third circumferential groove,
(4) A front triangular groove extending from the second circumferential groove toward the rear side and having a circumferential size and a depth that gradually decrease toward the rear side.
and
(5) A rear triangular groove extending from the third circumferential groove toward the front side and having a circumferential size and a depth that gradually decrease toward the front side.
It also has
A ratio of a width Wtf of the front triangular groove to a width Wr of a rib sandwiched between the second circumferential groove and the third circumferential groove is 0.10 or more and 0.30 or less,
The tire, in which a ratio of a width Wtb of the rear triangular groove to a width Wr of the rib is 0.10 or greater and 0.30 or less. A tire having a tread having a tread surface,
The above tread is
(1) a first circumferential groove located on an outer side of an equatorial plane of the tire;
(2) a second circumferential groove located on the rear side of the equatorial plane;
and
(3) a third circumferential groove located behind the second circumferential groove
It has
The first circumferential groove (1)
(1-1) Main section having front and back walls
and
(1-2) A subsection extending from the front side wall to the tread surface, the subsection having an inclination angle θ1s greater than the inclination angle θ1f of the front side wall.
It has
The width W1m of the main section is smaller than the width W2 of the second circumferential groove and smaller than the width W3 of the third circumferential groove,
(4) A front triangular groove extending from the second circumferential groove toward the rear side and having a circumferential size and a depth that gradually decrease toward the rear side.
and
(5) A rear triangular groove extending from the third circumferential groove toward the front side and having a circumferential size and a depth that gradually decrease toward the front side.
It also has
The inclination angle θtf of the bottom of the front triangular groove is 40° or more and 70° or less,
The tire, wherein the inclination angle θtb of the bottom of the rear triangular groove is 40° or more and 70° or less. (6) The tire according to claim 7 or 8 , further comprising a sipe connecting the front triangular groove and the rear triangular groove. The tire according to claim 9 , wherein the sipes have a depth Dp of 2.0 mm or more.

Images