tire

Abstract

To provide a tire which can achieve reduction of pattern noise while ensuring necessary chipping resistant performance and off-road performance.SOLUTION: At least two circumferential grooves 36 are engraved on a tread, and at least three land parts 38, which are arranged in an axial direction, are configured. The land part 38, which is positioned on an outer side in the axial direction, of three land parts 38 is a shoulder land part 38s. The shoulder land part 38s comprises a plurality of shoulder blocks 52 arranged in a circumferential direction. The shoulder land part 38s is divided into a grounded zone ZC from an equatorial plane side to a ground contact end PE and a non-grounded zone ZNC from the ground contact end PE to a treat end PT. A plurality of cylindrical first dimples 62 are engraved on the shoulder block 52 in the grounded zone ZC.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tire. [Background technology]

[0002] SUVs (Sports Utility Vehicles) run not only on paved roads but also on rough terrain. SUV tires have treads that are made up of many blocks carved into them with circumferential and lateral grooves. These tires are required to be quiet, as they are used for driving in urban areas.

[0003] When a tire comes into contact with the road surface, it hits the road surface. At this time, a sound (hereinafter, referred to as pattern noise) is generated. Loud pattern noise increases noise outside the vehicle. Aiming to improve the quietness of tires, studies on reducing pattern noise are being conducted (for example, see Patent Document 1 below). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-58839 A Summary of the Invention [Problem to be solved by the invention]

[0005] A thicker tread can reduce input when the tire comes into contact with the road. A thicker tread can also help reduce pattern noise. However, a thicker tread also increases the tire's mass and rolling resistance.

[0006] Siping the tread reduces the force exerted on the tire when it comes into contact with the road. Siping contributes to reducing pattern noise. However, there is concern that the sipes can become the starting point for cracks, reducing chipping resistance when driving on rough roads.

[0007] Reducing the groove volume of the axial grooves reduces pattern noise, but in this case, there is concern that off-road performance such as mud and rock performance may decrease.

[0008] It is difficult to achieve a good balance between quietness, chipping resistance, and off-road performance in SUV tires. There is a need to establish technology that can reduce pattern noise while maintaining the necessary chipping resistance and off-road performance.

[0009] The present invention has been made in consideration of the above circumstances, and has an object to provide a tire that can achieve reduced pattern noise while ensuring the necessary chipping resistance and off-road performance. [Means for solving the problem]

[0010] A tire according to one aspect of the present invention has a tread that comes into contact with a road surface. At least two circumferential grooves are formed in the tread to form at least three land portions aligned in the axial direction. Of the at least three land portions, the land portion located on the outer side in the axial direction is a shoulder land portion. The shoulder land portion has a plurality of shoulder blocks aligned in the circumferential direction. The shoulder land portion is divided into a ground contact zone from the equatorial plane side to the ground contact edge, and a non-ground contact zone from the ground contact edge to the edge of the tread. A plurality of cylindrical first dimples are formed in the shoulder blocks in the ground contact zone.

[0011] Preferably, in the tire, the first dimple has a diameter of 2 mm or greater and 5 mm or less.A ratio of a depth of the first dimple to a groove depth of the circumferential groove is 25% or greater and 65% or less.

[0012] Preferably, in the tire, the first dimples are spaced apart from one another from the equatorial plane side toward the end of the tread, and a ratio of the spacing between the first dimples to a width of the shoulder block is equal to or greater than 0.10 and is equal to or less than 0.20.

[0013] Preferably, in the tire, an angle that a wall surface of the first dimple forms with respect to a center line is greater than or equal to 0° and less than or equal to 30°.

[0014] Preferably, in the tire, the non-ground contact zone comprises a buttress portion extending in the circumferential direction between the shoulder block and the end of the tread, and a plurality of cylindrical second dimples are engraved in the buttress portion.

[0015] Preferably, in the tire, the second dimple has a diameter of 2 mm or greater and 5 mm or less.A ratio of a depth of the second dimple to a groove depth of the circumferential groove is 5% or greater and 15% or less.

[0016] Preferably, in the tire, the second dimples are spaced apart from one another in the circumferential direction, and the interval between the second dimples is equal to or greater than 5.0 mm and equal to or less than 10.0 mm.

[0017] Preferably, in the tire, an angle that a wall surface of the second dimple forms with respect to a center line is greater than or equal to 0° and less than or equal to 30°.

[0018] Preferably, in the tire, a ratio of a radial distance from the ground contact edge to an end of the tread to a section height is equal to or greater than 5% and is equal to or less than 15%.

[0019] A tire according to another aspect of the present invention has a tread that comes into contact with a road surface. At least two circumferential grooves are formed in the tread to form at least three land portions aligned in the axial direction. Of the at least three land portions, the land portion located on the outer side in the axial direction is a shoulder land portion. The shoulder land portion has a plurality of shoulder blocks aligned in the circumferential direction. The shoulder land portion is divided into a ground contact zone from the equatorial plane side to the ground contact edge, and a non-ground contact zone from the ground contact edge to the edge of the tread. Of the non-ground contact zone, a buttress portion extends circumferentially between the shoulder block and the edge of the tread, and a plurality of cylindrical second dimples are formed in the buttress portion. Effect of the Invention

[0020] According to the present invention, a tire can be obtained that can achieve reduced pattern noise while ensuring the required chipping resistance and off-road performance. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a cross-sectional view showing a part of a tire according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a development view showing the tread surface of the tire. [Diagram 3] FIG. 3 is a perspective view showing a portion of the tread. [Figure 4] FIG. 4 is a cross-sectional view of the first dimple. [Diagram 5] FIG. 5 is a cross-sectional view of the second dimple. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

[0023] In this disclosure, a state in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to a standard internal pressure, and no load is applied to the tire is referred to as a standard state. In the present invention, unless otherwise specified, the dimensions and angles of each part of the tire are measured in the standard state.

[0024] Genuine rims are rims that are specified in the standards on which the tires are based. "Standard rims" in the JATMA standard, "Design Rim" in the TRA standard, and "Measuring Rim" in the ETRTO standard are genuine rims.

[0025] Normal internal pressure means the internal pressure specified in the standard on which the tire is based. The "maximum air pressure" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are normal internal pressures. If the tire is for passenger cars, the normal internal pressure is 180kPa unless otherwise specified.

[0026] The normal load means the load specified in the standard on which the tire is based. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads. If the tire is for passenger cars, the normal load is a load equivalent to 88% of the above load, unless otherwise specified.

[0027] In this disclosure, the load index (LI) is an index that is defined, for example, in the JATMA standard and indicates the maximum mass that can be loaded onto a tire under specified conditions, that is, the maximum load capacity.

[0028] FIG. 1 shows an example of a pneumatic tire 2 (hereinafter, tire 2) according to one embodiment of the present invention. This tire 2 is mounted on a passenger vehicle. More specifically, this tire 2 is mounted on an SUV (Sports Utility Vehicle), such as a 4WD vehicle, designed for running not only on paved roads but also on rough ground. In FIG. 1, the tire 2 is mounted on a rim R. The rim R is a regular rim. Air is filled inside the tire 2, and the internal pressure of the tire 2 is adjusted to a regular internal pressure.

[0029] Fig. 1 shows a part of a cross section of the tire 2 taken along a plane including the rotation axis of the tire 2. In Fig. 1, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. The direction perpendicular to the plane of Fig. 1 is the circumferential direction of the tire 2. In Fig. 1, a dashed dotted line CL represents the equatorial plane of the tire 2.

[0030] In Fig. 1, the solid line BBL extending in the axial direction is the bead base line. This bead base line is a line that defines the rim diameter of the rim R (see JATMA, etc.).

[0031] The tire 2 includes a tread 4, a pair of sidewalls 6, a pair of clinches 8, a pair of beads 10, a carcass 12, a belt 14, a band 16, a pair of chafers 18, a pair of fillers 20, and an inner liner 22. In the tire 2, the sidewalls 6, the clinches 8, the beads 10, the carcass 12, the belt 14, the band 16, the chafers 18, the fillers 20, and the inner liner 22 are configured based on technology generally used in SUV tires. Detailed description of these will be omitted.

[0032] The tread 4 comes into contact with the road surface at its outer surface, i.e., the tread surface 24. In FIG. 1, the position indicated by the symbol PE is a specific position on the tread surface 24. The specific position PE corresponds to the axially outer end of the contact surface of the tire 2 with the road surface. In this tire 2, the specific position PE is the contact edge. The contact edge PE is a position on the outer surface of the tire 2 that corresponds to the axially outer end of the contact surface of the tire 2 with the road surface.

[0033] The contact patch for identifying the contact edge PE is obtained, for example, by using a contact patch shape measuring device (not shown). This contact patch is obtained by mounting the tire 2 on the rim R, adjusting the internal pressure of the tire 2 to 230 kPa, setting the camber angle of the tire 2 to 0°, applying a load equivalent to 70% of the mass represented by the load index as a vertical load to the tire 2, and bringing the tire 2 into contact with a flat road surface.

[0034] The tread 4 includes a tread body 26 and a pair of wings 28. The tread body 26 includes a base layer 30 and a cap layer 32.

[0035] The base layer 30 is laminated to the band 16. The base layer 30 is made of a crosslinked rubber with low heat generation. The cap layer 32 is located radially outside the base layer 30. The cap layer 32 covers the entire base layer 30. The cap layer 32 is made of a crosslinked rubber with consideration given to abrasion resistance and grip performance. The outer surface of the cap layer 32 forms a part of the tread surface 24.

[0036] Each of the wings 28 is located axially outward of the tread body 26. In the tire 2, the tread body 26 and the sidewall 6 are joined via the wings 28. The wings 28 are made of crosslinked rubber with adhesive properties taken into consideration.

[0037] In this tire 2, the tread surface 24 is composed of the outer surface of the cap layer 32 and the outer surfaces of the wings 28. In Fig. 1, the symbol PT is the end of the tread surface 24, in other words, the end of the tread 4. The end PT of the tread 4 is also the boundary between the tread 4 and the sidewall 6 on the outer surface of the tire 2. The boundary between the cap layer 32 and the wings 28 on the outer surface of the tire 2 is provided axially outward of the ground contact edge PE, but the specific position is appropriately determined in consideration of the specifications of the tire 2.

[0038] In Fig. 1, the symbol PC is the equator of the tire 2. The equator PC is represented by the intersection of the tread surface 24 and the equatorial plane. In Fig. 1, the length represented by the double arrow HS is the section height of the tire 2 (see JATMA, etc.). The section height HS is represented by the radial distance from the bead base line to the equator PC. In this tire 2, the section height HS is measured in a normal state.

[0039] Fig. 2 shows a part of the tread surface 24. In Fig. 2, the left-right direction is the axial direction of the tire 2, and the up-down direction is the circumferential direction of the tire 2. The direction perpendicular to the paper surface of Fig. 2 is the radial direction of the tire 2.

[0040] Grooves 34 are formed in the tread 4 of the tire 2. This forms a tread pattern. At least two circumferential grooves 36 extending in the circumferential direction are formed in the tread 4 as the grooves 34 forming the tread pattern. This forms at least three land portions 38 aligned in the axial direction in the tread 4. In the tire 2, four circumferential grooves 36 are formed in the tread 4, forming five land portions 38 in the tread 4. Among the grooves 34 forming the tread pattern, the grooves 34 having a groove width of 2.0 mm or less are called sipes.

[0041] In the tire 2, the four circumferential grooves 36 are continuous in the circumferential direction. As shown in Fig. 2, the circumferential grooves 36 extend in a serpentine manner. The circumferential grooves 36 may be configured to extend in a zigzag manner or may be configured to extend in a straight line.

[0042] In the tire 2, of the four circumferential grooves 36, the circumferential groove 36 located on the outer side in the axial direction is the shoulder circumferential groove 36s. The circumferential groove 36 located on the inner side of the shoulder circumferential groove 36s is the middle circumferential groove 36m. In the tire 2, the four circumferential grooves 36 include a pair of middle circumferential grooves 36m arranged on either side of the equatorial plane, and a pair of shoulder circumferential grooves 36s each located on the outer side of the middle circumferential groove 36m.

[0043] In Fig. 2, the double-headed arrow WE indicates the axial distance from one ground contact end PE to the other ground contact end PE. In this tire 2, this axial distance WE is the ground contact width. The double-headed arrow GM indicates the groove width of the middle circumferential groove 36m. The double-headed arrow GS indicates the groove width of the shoulder circumferential groove 36s. The ground contact width WE, groove width GM, and groove width GS are measured in a development view of the tread surface 24.

[0044] In the tire 2, from the viewpoint of adjusting the rigidity of the tread 4 while ensuring drainage, the ratio (GM / WE) of the groove width GM of the middle circumferential groove 36m to the ground contact width WE is preferably 0.035 or more and 0.060 or less. From the same viewpoint, the ratio (GS / WE) of the groove width GS of the shoulder circumferential groove 36s to the ground contact width WE is preferably 0.035 or more and 0.060 or less.

[0045] 1, the double arrow DM indicates the groove depth of the middle circumferential groove 36m. The double arrow DS indicates the groove depth of the shoulder circumferential groove 36s. The groove depths DM and DS are measured on the tire 2 in a normal state.

[0046] In the tire 2, from the viewpoint of adjusting the rigidity of the tread 4 while ensuring drainage, the ratio (DM / WE) of the groove depth DM of the middle circumferential groove 36m to the contact width WE is preferably 0.040 or more and 0.085 or less. From the same viewpoint, the ratio (DS / WE) of the groove depth DS of the shoulder circumferential groove 36s to the contact width WE is preferably 0.040 or more and 0.085 or less.

[0047] In the tire 2, of the five land portions 38, the land portion 38 located on the outer side in the axial direction is the shoulder land portion 38s. The land portion 38 located on the inner side of the shoulder land portion 38s is the middle land portion 38m. The land portion 38 located on the inner side of the middle land portion 38m is the center land portion 38c. In the tire 2, the center land portion 38c is between the two middle circumferential grooves 36m, and the center land portion 38c is located on the equatorial plane. The middle land portion 38m is between the middle circumferential groove 36m and the shoulder circumferential groove 36s. The shoulder land portion 38s is located on the outer side of the shoulder circumferential groove 36s in the axial direction and includes the ground contact edge PE. The five land portions 38 include the center land portion 38c, a pair of middle land portions 38m, and a pair of shoulder land portions 38s.

[0048] In FIG. 2, the double-headed arrow WC indicates the width of the center land portion 38c. The width WC is represented by the axial distance from one axially outer end to the other axially outer end of the center land portion 38c. The double-headed arrow WM indicates the width of the middle land portion 38m. The width WM is represented by the axial distance from one axially inner end to the other axially outer end of the middle land portion 38m. The double-headed arrow WS indicates the width of the shoulder land portion 38s. The width WS is represented by the axial distance from the axially inner end of the shoulder land portion 38s to the ground contact edge PE. The width WS is the width of the shoulder land portion 38s included in the ground contact surface. The widths WC, WM, and WS are measured in a development view of the tread surface 24.

[0049] In the tire 2, from the viewpoint of adjusting the rigidity of the tread 4 while ensuring drainage, the ratio (WC / WE) of the width WC of the center land portion 38c to the contact width WE is preferably 0.10 or more and 0.20 or less. From the same viewpoint, the ratio (WM / WE) of the width WM of the middle land portion 38m to the contact width WE is preferably 0.12 or more and 0.22 or less. From the same viewpoint, the ratio (WS / WE) of the width WS of the shoulder land portion 38s to the contact width WE is preferably 0.15 or more and 0.25 or less.

[0050] In the center land portion 38c of the tire 2, a plurality of lateral grooves (hereinafter, center lateral grooves 40) are formed as grooves 34 constituting the tread pattern. These center lateral grooves 40 are arranged at intervals in the circumferential direction. Each center lateral groove 40 has an end in the center land portion 38c. This end is located on the equatorial plane, and the center lateral groove 40 connects this end to the middle circumferential groove 36m. As shown in FIG. 2, the center lateral grooves 40 provided on one edge of the center land portion 38c and the center lateral grooves 40 provided on the other edge are arranged alternately in the circumferential direction. The groove width and groove depth of the center lateral grooves 40 are appropriately determined in consideration of the specifications of the tire 2.

[0051] A plurality of lateral grooves (hereinafter, middle lateral grooves 42) are formed in the middle land portion 38m of the tire 2 as grooves 34 constituting the tread pattern. These middle lateral grooves 42 are arranged at intervals in the circumferential direction. Each middle lateral groove 42 connects the middle circumferential groove 36m and the shoulder circumferential groove 36s. The groove width and groove depth of the middle lateral grooves 42 are appropriately determined in consideration of the specifications of the tire 2.

[0052] The middle lateral grooves 42 cross the middle land portion 38m. A plurality of blocks (hereinafter, middle blocks 44) are formed by forming a plurality of middle lateral grooves 42 in the middle land portion 38m. The middle land portion 38m includes a plurality of middle blocks 44 arranged in the circumferential direction.

[0053] One open sipe 46 and two dead-end sipes 48 are formed as grooves 34 (more specifically, sipes) that constitute the tread pattern in the middle block 44 of the tire 2. In the tire 2, the groove width of the open sipe 46 and the dead-end sipe 48 is 1.0 mm or less.

[0054] The open sipe 46 connects the middle circumferential groove 36m and the shoulder circumferential groove 36s. Two dead-end sipes 48 are arranged on either side of the open sipe 46. Each dead-end sipe 48 has an end within the middle block 44. One dead-end sipe 48 connects the end to the middle circumferential groove 36m. The other dead-end sipe 48 connects the end to the shoulder circumferential groove 36s.

[0055] A plurality of lateral grooves (hereinafter, shoulder lateral grooves 50) are formed in the shoulder land portion 38s of the tire 2 as grooves 34 constituting the tread pattern. These shoulder lateral grooves 50 are arranged at intervals in the circumferential direction. Each shoulder lateral groove 50 extends from the shoulder circumferential groove 36s toward the edge PT of the tread 4. The groove width and groove depth of the shoulder lateral groove 50 are appropriately determined in consideration of the specifications of the tire 2.

[0056] The shoulder lateral groove 50 crosses the shoulder land portion 38s. A plurality of blocks (hereinafter, shoulder blocks 52) are formed by cutting a plurality of shoulder lateral grooves 50 in the shoulder land portion 38s. The shoulder land portion 38s includes a plurality of shoulder blocks 52 arranged in the circumferential direction.

[0057] In this tire 2, as shown in FIG. 2, a plurality of longitudinal grooves 54 are formed on the axially outer portion of the shoulder block 52 as grooves 34 constituting the tread pattern. The longitudinal grooves 54 are arranged at intervals in the circumferential direction. Each longitudinal groove 54 connects the ends of two shoulder lateral grooves 50. In the shoulder land portion 38s of this tire 2, shoulder blocks 52 with longitudinal grooves 54 formed therein and shoulder blocks 52 without longitudinal grooves 54 formed therein are arranged alternately in the circumferential direction. The groove width and groove depth of the longitudinal grooves 54 are appropriately determined in consideration of the specifications of the tire 2.

[0058] Wide sipes 56 are formed in the shoulder blocks 52 of this tire as grooves 34 (more specifically, sipes) that constitute the tread pattern. The groove width of the wide sipes 56 is wider than the groove width of the open sipes 46 and the dead-end sipes 48 described above.

[0059] The wide sipes 56 have ends within the shoulder blocks 52. The wide sipes 56 connect the ends to the shoulder circumferential grooves 36s. A recess 58 is further formed on the outer side of the wide sipes 56 in the shoulder blocks 52 of the tire 2. The wide sipes 56 connect to the recess 58 at their ends.

[0060] 3 shows the shoulder land portion 38s of the tread 4. In this tire 2, a plurality of cylindrical dimples 60 are engraved in the shoulder block 52. These dimples 60 are circular holes and extend inward from the outer surface of the shoulder block 52.

[0061] Ten dimples 60 are engraved on the shoulder block 52 of this tire 2. There is no particular limit to the number of dimples 60 provided on the shoulder block 52 of this tire 2. The number of dimples 60 is determined appropriately taking into consideration the size of the shoulder block 52 and the effect of providing the dimples 60 on performance.

[0062] In the tire 2, as long as a plurality of dimples 60 are scattered on the outer surface of the shoulder block 52, there is no particular limitation on the arrangement of these dimples 60.

[0063] This tire 2 is configured with two dimple rows, each consisting of five dimples 60. As shown in Fig. 3, the two dimple rows are arranged with a wide sipe 56 in between. In this tire 2, in each dimple row, the five dimples 60 are arranged at intervals from the equatorial plane side (more specifically, the edge on the shoulder circumferential groove 36s side) toward the end PT of the tread 4.

[0064] In this tire 2, the number of dimple rows provided in the shoulder blocks 52 and the number of dimples 60 included in one dimple row are determined appropriately, taking into consideration the size of the shoulder blocks 52 and the effect of providing the dimples 60 on performance. In this tire 2, from the viewpoint of achieving the effect of providing the dimples 60, the number of dimple rows provided in the shoulder blocks 52 is preferably one or more and preferably three or less. A more preferable number of dimple rows is two. The number of dimples 60 included in one dimple row is preferably five or more and preferably ten or less.

[0065] As described above, the shoulder land portion 38s includes the ground contact edge PE. As shown in Fig. 2, the shoulder land portion 38s is divided into a ground contact zone ZC from the equator side to the ground contact edge PE and a non-ground contact zone ZNC from the ground contact edge PE to the tread edge PT.

[0066] 2, a plurality of dimples 60 (specifically, six dimples 60) are provided on the shoulder block 52 in the ground contact zone ZC. In the tire 2, the dimples 60 provided in the ground contact zone ZC are first dimples 62.

[0067] The rigidity of the shoulder blocks 52 affects the generation of pattern noise. In this tire 2, a plurality of cylindrical first dimples 62 are engraved on the shoulder blocks 52 in the contact zone ZC. Since the rigidity of the shoulder blocks 52 is appropriately reduced, the impact when the tread 4 hits the road surface is suppressed. Since the input at the time of contact with the road is mitigated, the pattern noise is reduced. In this tire 2, quietness is improved.

[0068] In this tire 2, in order to reduce pattern noise, it is not necessary to employ a thick tread for the tread 4. On the contrary, the first dimples 62 contribute to reducing the mass of the tread 4. In this tire 2, weight reduction and reduction in rolling resistance are achieved.

[0069] In this tire 2, the first dimples 62 are cylindrical and therefore are less likely to become the starting point of cracks, unlike sipes. Even when this tire 2 runs on rough roads, the occurrence of cracks that would be observed if sipes were added is suppressed. In this tire 2, good chipping resistance is maintained even though the first dimples 62 are provided in the shoulder blocks 52.

[0070] Since the first dimples 62 are so-called holes, the first dimples 62 contribute to scraping off mud when traveling on rough roads such as muddy ground. With this tire 2, good mud performance is obtained. When traveling on a rocky road surface consisting of bedrock, the shoulder blocks 52, the rigidity of which is appropriately reduced by the first dimples 62, can adequately grip the rocks. This tire 2 can run firmly on rocky road surfaces. With this tire 2, good locking performance is obtained. This tire 2 has excellent off-road performance.

[0071] This tire 2 can achieve a reduction in pattern noise while ensuring the necessary chipping resistance and off-road performance. The necessary chipping resistance and off-road performance mean a level that is acceptable as being equivalent to that of conventional tires.

[0072] In this tire 2, within the non-contact zone ZNC, between the shoulder block 52 and the end PT of the tread 4 is a buttress portion 64. In this tire 2, the radially inner end of the buttress portion 64 is the end PT of the tread 4. The radially outer end of the buttress portion 64 is the axially outer end of the shoulder block 52. The buttress portion 64 extends in the circumferential direction.

[0073] In this tire 2, a plurality of cylindrical dimples (hereinafter, second dimples 66) are engraved in the buttress portion 64. These second dimples 66 are arranged at intervals in the circumferential direction. In this tire 2, one dimple row is formed from a plurality of second dimples aligned in the circumferential direction. A plurality of dimple rows may be formed in this buttress portion 64.

[0074] The second dimples 66 provided on the buttress portion 64 reduce the rigidity of the shoulder land portion 38s. In the tire 2, the second dimples 66 contribute to suppressing the impact when the tread 4 hits the road surface. Since the input at the time of contact with the road is mitigated, the pattern noise is reduced. In the tire 2, quietness is improved.

[0075] In this tire 2, in order to reduce pattern noise, it is not necessary to employ a thick tread for the tread 4. On the contrary, the second dimples 66 contribute to reducing the mass of the tread 4. In this tire 2, weight reduction and reduction in rolling resistance are achieved.

[0076] In this tire 2, the second dimples 66 are cylindrical and therefore unlikely to become the starting point of cracks. Even when this tire 2 runs on a rough road and the buttress portion 64 comes into contact with the rough road, the occurrence of cracks starting from this second dimple 66 is suppressed. In this tire 2, despite the fact that the second dimples 66 are provided in the buttress portion 64, good chipping resistance is maintained.

[0077] Since the second dimples 66 are so-called holes, when the buttress portion 64 comes into contact with a rough road, the second dimples 66 contribute to scraping off mud. The second dimples 66 contribute to improving mud performance. Since the second dimples 66 contribute to reducing the rigidity of the shoulder land portion 38s, even when the buttress portion 64 comes into contact with a rocky road surface, the shoulder land portion 38s can adequately grip rocks. The tire 2 can run firmly on rocky road surfaces. The second dimples 66 contribute to improving locking performance. The second dimples 66 contribute to improving off-road performance.

[0078] In this tire 2, the necessary chipping resistance and off-road performance are ensured and pattern noise is reduced by carving a plurality of second dimples 66 into the buttress portion 64. From this viewpoint, in this tire 2, it is preferable that a plurality of cylindrical second dimples 66 are carved into the buttress portion 64.

[0079] In the tire 2 shown in FIG. 1, a plurality of first dimples 62 are carved in the shoulder blocks 52 in the ground contact zone ZC, and a plurality of second dimples 66 are carved in the buttress portion 64 in the non-ground contact zone ZNC. In this tire 2, a plurality of first dimples 62 may be carved only in the shoulder blocks 52 in the ground contact zone ZC, without carving the second dimples 66 in the buttress portion 64. A plurality of second dimples 66 may be carved only in the buttress portion 64 in the non-ground contact zone ZNC, without carving the first dimples 62 in the shoulder blocks 52 in the ground contact zone ZC. From the viewpoint of sufficiently reducing pattern noise while effectively ensuring the required chipping resistance and off-road performance, it is more preferable that a plurality of first dimples 62 are carved in the shoulder blocks 52 in the ground contact zone ZC, and a plurality of second dimples 66 are carved in the buttress portion 64 in the non-ground contact zone ZNC, as shown in FIG. 2 and FIG. 3. In this case, the first dimples 62 and the second dimples 66 may be configured to have the same specifications or different specifications.

[0080] 1, the double-headed arrow HB indicates the radial distance from the ground contact edge PE to the edge PT of the tread 4. In this tire 2, the radial distance HB is measured in a normal state.

[0081] In this tire 2, from the viewpoint that the second dimples 66 engraved in the buttress portion 64 can effectively contribute to ensuring the necessary chipping resistance and off-road performance and reducing pattern noise, the ratio of the radial distance HB to the cross-sectional height HS (HB / HS) is preferably 5% or more and 15% or less.

[0082] 2, the double-headed arrow WB indicates the axial distance from the axially inner end to the axially outer end of the shoulder block 52. In the tire 2, the axial distance WB is the width of the shoulder block 52. The double-headed arrow S1 indicates the spacing between the first dimples 62. This spacing S1 is represented as the shortest distance between adjacent first dimples 62. The double-headed arrow S2 indicates the spacing between the second dimples 66. This spacing S2 is represented as the shortest distance between adjacent second dimples 66. The width WB, spacing S1, and spacing S2 are measured in a developed view of the tread surface 24.

[0083] In this tire 2, from the viewpoint of ensuring the necessary chipping resistance performance, the ratio (S1 / WB) of the spacing S1 of the first dimples 62 to the width WB of the shoulder block 52 is preferably equal to or greater than 0.10, and more preferably equal to or greater than 0.13. From the viewpoints of ensuring the necessary off-road performance and reducing pattern noise, the ratio (S1 / WB) is preferably equal to or less than 0.20, and more preferably equal to or less than 0.17.

[0084] In this tire 2, from the viewpoint of ensuring the necessary chipping resistance performance, the interval S2 between the second dimples is preferably 5.0 mm or more, and more preferably 6.5 mm or more. From the viewpoint of ensuring the necessary off-road performance and reducing pattern noise, the interval S2 is preferably 10.0 mm or less, and more preferably 8.5 mm or less.

[0085] Fig. 4 shows a cross section of the first dimple 62. The dashed dotted line C1 is the center line of the first dimple 62. As shown in Fig. 4, the first dimple 62 tapers toward a bottom 68. This first dimple 62 may be configured in a cylindrical shape. In Fig. 4, an angle θ1 is the angle that a wall surface 70 of the first dimple 62 makes with respect to the center line C1. In this tire 2, this angle θ1 is set in the range of 0° or more and 30° or less.

[0086] 4, the double-headed arrow A1 indicates the diameter of the first dimple 62. In this tire 2, the diameter A1 is represented as the diameter at the opening edge of the first dimple 62. The double-headed arrow D1 indicates the depth of the first dimple 62. The depth D1 is represented as the distance from the opening edge to the bottom 68 of the first dimple 62.

[0087] In this tire 2, the diameter A1 of the first dimple 62 is preferably 2 mm or more, and preferably 5 mm or less. By setting the diameter A1 to 2 mm or more, the first dimple 62 effectively contributes to ensuring the required off-road performance and reducing pattern noise. From this viewpoint, the diameter A1 is more preferably 3 mm or more. By setting the diameter A1 to 5 mm or less, the first dimple 62 effectively contributes to ensuring the required chipping resistance performance. From this viewpoint, the diameter A1 is more preferably 4 mm or less.

[0088] In the tire 2, the ratio (D1 / DS) of the depth D1 of the first dimple 62 to the groove depth DS of the circumferential groove 36, specifically, the shoulder circumferential groove 36s that defines the shoulder land portion 38s, is preferably 25% or more and preferably 65% ​​or less. By setting the ratio (D1 / DS) to 25% or more, the first dimple 62 effectively contributes to ensuring the required off-road performance and reducing pattern noise. From this viewpoint, the ratio (D1 / DS) is more preferably 30% or more and more preferably 35% or more. By setting the ratio (D1 / DS) to 65% or less, the first dimple 62 effectively contributes to ensuring the required chipping resistance performance. From this viewpoint, the ratio (D1 / DS) is more preferably 60% or less and more preferably 55% or less.

[0089] From the viewpoint of enabling the first dimple 62 to more effectively contribute to ensuring the necessary chipping resistance and off-road performance and reducing pattern noise, it is more preferable that the diameter A1 of the first dimple 62 be 2 mm or more and 5 mm or less, and that the ratio (D1 / DS) of the depth D1 of the first dimple 62 to the groove depth DS of the shoulder circumferential groove 36s be 25% or more and 65% or less.

[0090] Fig. 5 shows a cross section of the second dimple 66. The dashed dotted line C2 is the center line of the second dimple 66. As shown in Fig. 5, the second dimple 66 tapers toward a bottom 72. This second dimple 66 may be configured in a cylindrical shape. In Fig. 5, an angle θ2 is an angle that a wall surface 74 of the second dimple 66 makes with respect to the center line C2. In this tire 2, this angle θ2 is set in the range of 0° or more and 30° or less.

[0091] 5, the double-headed arrow A2 indicates the diameter of the second dimple 66. In this tire 2, the diameter A2 is represented as the diameter at the opening edge of the second dimple 66. The double-headed arrow D2 indicates the depth of the second dimple 66. The depth D2 is represented as the distance from the opening edge to the bottom 72 of the second dimple 66.

[0092] In the tire 2, the diameter A2 of the second dimple 66 is preferably 2 mm or more, and preferably 5 mm or less. By setting the diameter A2 to 2 mm or more, the second dimple 66 effectively contributes to ensuring the required off-road performance and reducing pattern noise. From this viewpoint, the diameter A2 is more preferably 3 mm or more. By setting the diameter A2 to 5 mm or less, the second dimple 66 effectively contributes to ensuring the required chipping resistance performance. From this viewpoint, the diameter A2 is more preferably 4 mm or less.

[0093] In the tire 2, the ratio (D2 / DS) of the depth D2 of the second dimple 66 to the groove depth DS of the circumferential groove 36, specifically, the shoulder circumferential groove 36s that defines the shoulder land portion 38s, is preferably 5% or more and preferably 15% or less. By setting the ratio (D2 / DS) to 5% or more, the second dimple 66 effectively contributes to ensuring the required off-road performance and reducing pattern noise. From this viewpoint, the ratio (D2 / DS) is more preferably 8% or more. By setting the ratio (D2 / DS) to 15% or less, the second dimple 66 effectively contributes to ensuring the required chipping resistance performance. From this viewpoint, the ratio (D2 / DS) is more preferably 12% or less.

[0094] From the viewpoint of enabling the second dimple 66 to more effectively contribute to ensuring the necessary chipping resistance and off-road performance and reducing pattern noise, it is more preferable that the diameter A2 of the second dimple 66 is 2 mm or more and 5 mm or less, and that the ratio (D2 / DS) of the depth D2 of the second dimple 66 to the groove depth DS of the shoulder circumferential groove 36s is 5% or more and 15% or less.

[0095] As shown in FIG. 2, in the tire 2, a plurality of dimples 60 are also provided between the ground contact zone ZC and the buttress portion 64.

[0096] The contact patch shape of the tire 2 in a running state changes depending on the situation. Depending on the situation, the contact edge may be located outside the reference contact edge PE. In this case, of the multiple dimples located between the contact zone ZC and the buttress portion 64, the dimple 60 located on the contact zone ZC side is included in the contact patch. This dimple 60 functions as a first dimple 62. Off-road, the radially outer portion of the buttress portion 64 also comes into contact with the road surface. In this case, of the multiple dimples 60 located between the contact zone ZC and the buttress portion 64, the dimple 60 located on the buttress portion 64 side functions as a second dimple 66.

[0097] In this tire 2, the multiple dimples 60 located between the ground contact zone ZC and the buttress portion 64 also effectively contribute to ensuring the necessary chipping resistance and off-road performance, and reducing pattern noise. From this perspective, it is preferable that multiple cylindrical dimples 60 (hereinafter, third dimples 76) are also engraved in the shoulder block 52 between the ground contact zone ZC and the buttress portion 64. In this case, the third dimples 76 are engraved in the shoulder block 52, and therefore the third dimples 76 are configured to the same specifications as the first dimples 62.

[0098] As described above, according to the present invention, it is possible to obtain a tire 2 that can achieve reduction in pattern noise while ensuring necessary chipping resistance and off-road performance. This tire 2 exerts a particularly remarkable effect when used as a tire for SUVs. EXAMPLES

[0099] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0100] [Example 1] An SUV tire (tire size=265 / 65R18) having the basic structure shown in FIG. 1-3 and the specifications shown in Table 1 below was obtained.

[0101] In this Example 1, dimples were engraved on the shoulder blocks and buttress portions. This is indicated by a "D" in the tread column in Table 1.

[0102] The diameter of the dimple engraved in the shoulder block was 3.5 mm, the ratio of the depth of this dimple to the groove depth DS of the shoulder circumferential groove was 45%, and the ratio of the spacing between this dimple to the width WB of the shoulder block was 0.13. Of the dimples engraved in the shoulder block, the dimples included in the ground contact zone ZC are first dimples, and so the diameter A1 of the first dimples was 3.5 mm, the ratio (D1 / DS) of the depth D1 of the first dimple to the groove depth DS of the shoulder circumferential groove was 45%, and the ratio (S1 / WB) of the spacing S1 between the first dimples to the width WB of the shoulder block was 0.13.

[0103] The diameter A2 of the dimples engraved in the buttress portion, i.e., the second dimples, was 3.5 mm, the ratio (D2 / DS) of the depth D2 of the second dimples to the groove depth DS of the shoulder circumferential groove was 10%, and the spacing S2 of the second dimples was 7.5 mm.

[0104] [Comparative Example 1] A tire of Comparative Example 1 was obtained in the same manner as in Example 1, except that no dimples were engraved on the shoulder blocks and buttress portions.

[0105] [Comparative Example 2] A tire of Comparative Example 2 was obtained in the same manner as Comparative Example 1, except that the tread was configured to be 1 mm thicker than the thickness of the tread of Comparative Example 1. The use of a thick tread is indicated by a "T" in the tread column of Table 1 below. Comparative Example 2 is a tire that uses a thick tread as a measure to reduce pattern noise.

[0106] [Comparative Example 3] A tire of Comparative Example 3 was obtained in the same manner as Comparative Example 1, except that sipes were cut into the shoulder blocks of Comparative Example 1. The use of a tread with sipes cut into the shoulder blocks is indicated by "S" in the tread column in Table 1 below. Comparative Example 3 is a tire that uses a tread with sipes cut into the shoulder blocks as a measure to reduce pattern noise.

[0107] [Example 2] A tire of Example 2 was obtained in the same manner as Example 1, except that no dimples were engraved on the buttress portion.

[0108] [Example 3] A tire of Example 3 was obtained in the same manner as in Example 1, except that no dimples were engraved on the shoulder blocks.

[0109] [Example 4-5] The tires of Examples 4 and 5 were obtained in the same manner as Example 1, except that the outer diameters of the dimples engraved on the shoulder blocks and buttress portions were changed so that the diameter A1 of the first dimples and the diameter A2 of the second dimples were as shown in Table 2 below.

[0110] [Examples 6-7] The tires of Examples 6 and 7 were obtained in the same manner as Example 1, except that the depth of the dimples engraved in the shoulder blocks and buttress portions was changed so that the ratios (D1 / DS) and (D2 / DS) were as shown in Table 2 below.

[0111] [Examples 8-9] Tires of Examples 8 and 9 were obtained in the same manner as in Example 1, except that the number of dimples engraved on the buttress portion was adjusted so that the spacing S2 between the second dimples was as shown in Table 3 below.

[0112] [Examples 10-11] Tires of Examples 10 and 11 were obtained in the same manner as in Example 1, except that the number of dimples engraved in the shoulder blocks was adjusted so that the ratio (S1 / WB) was as shown in Table 3 below.

[0113] [Driving performance] The prototype tire was mounted on a rim (size = 8.0J) and filled with air to adjust the tire's internal pressure to 230 kPa. The tire was mounted on a test vehicle (SUV), and the driver drove the test vehicle on a test course that included dry asphalt, mud, and rock surfaces. To evaluate quietness, the occurrence of pattern noise on dry asphalt surfaces was confirmed. To evaluate off-road performance, a sensory evaluation was conducted regarding the degree of traction on mud and rock surfaces. These results are shown as indices in Table 1-3 below. For quietness, the higher the numerical value, the greater the reduction in pattern noise. For off-road performance, the higher the numerical value, the better the traction.

[0114] [Chipping resistance] The appearance of the tires after the above-mentioned driving performance evaluation was observed to check the occurrence of chipping. The results are shown as an index in Table 1-3 below. The higher the number, the more chipping is suppressed. In this evaluation, even if the index is less than 100, if it is 95 or more, it is considered that the decrease in chipping resistance has been suppressed and is acceptable.

[0115] [Overall performance] The total value of quietness, off-road performance, and chipping resistance is shown as the overall performance in Table 1-3 below. The higher the value, the better.

[0116] [Table 1]

[0117] [Table 2]

[0118] [Table 3]

[0119] As shown in Tables 1-3, the Examples show that the pattern noise is reduced while maintaining the necessary chipping resistance and off-road performance, as compared to the Comparative Examples. Comparative Example 2 has the same performance as the Examples in terms of quietness, off-road performance, and chipping resistance. However, in Comparative Example 2, an increase in rolling resistance has been confirmed due to the adoption of a thick tread. In contrast, the Examples show a reduction in rolling resistance. From the above evaluation results, the superiority of the present invention is clear. [Industrial Applicability]

[0120] The technology described above for reducing pattern noise while ensuring the necessary chipping resistance and off-road performance can be applied to various types of tires. [Explanation of symbols]

[0121] 2. Tires 4. Tread 24 Tread surface 36, 36s, 36m...Circumferential groove 38, 38s, 38m, 38c...Land 52 Shoulder block 60···Dimples 62 First dimple 64...Buttress section 66...Second dimple 76 Third dimple

Claims

1. A tire having a tread that comes into contact with a road surface, At least two circumferential grooves are formed in the tread to define at least three land portions aligned in the axial direction; Among the at least three land portions, a land portion located on an outer side in the axial direction is a shoulder land portion, The shoulder land portion includes a plurality of shoulder blocks arranged in a circumferential direction, The shoulder land portion is divided into a ground contact zone from the equator side to a ground contact edge and a non-ground contact zone from the ground contact edge to an edge of the tread, A plurality of cylindrical first dimples are formed on the shoulder block in the ground contact zone; The diameter of the first dimple is 3 mm or more and 4 mm or less, a ratio of a depth of the first dimple to a groove depth of the circumferential groove is 35% or more and 55% or less; The first dimples are spaced apart from one another from an equatorial plane side toward an end of the tread, a ratio of the spacing between the first dimples to the width of the shoulder block is 0.13 or greater and 0.17 or less; In the non-ground contact zone, a buttress portion extends in a circumferential direction between the shoulder block and an end of the tread, A plurality of cylindrical second dimples are engraved on the buttress portion, The diameter of the second dimple is 3 mm or more and 4 mm or less, a ratio of a depth of the second dimple to a groove depth of the circumferential groove is 8% or more and 12% or less; the plurality of second dimples are circumferentially spaced apart; The interval between the second dimples is 6.5 mm or more and 8.5 mm or less. Tires for SUVs.

2. an angle that a wall surface of the first dimple forms with respect to a center line is equal to or greater than 0° and equal to or less than 30°; 2. The tire for an SUV according to claim 1.

3. an angle that a wall surface of the second dimple forms with respect to a center line is equal to or greater than 0° and equal to or less than 30°; 3. The tire for SUVs according to claim 1 or 2.

4. The ratio of the radial distance from the ground contact end to the end of the tread to the cross-sectional height is 5% or more and 15% or less. The tire for an SUV according to any one of claims 1 to 3.

5. The tread end is located radially inward of the axially outer end of the shoulder block, A zone from an axially outer end of the shoulder block to an end of the tread constitutes the buttress portion.

5. The tire for an SUV according to claim 1 .

6. A plurality of cylindrical third dimples are engraved on the shoulder block between the ground contact zone and the buttress portion, the third dimple has a diameter and a depth equal to the diameter and depth of the first dimple; In the shoulder block, following the first dimple on the tread end side, a plurality of the third dimples are arranged at intervals from the equatorial plane side toward the tread end.

6. The tire for an SUV according to claim 5.

Images