pneumatic tires

Abstract

To provide a pneumatic tire capable of suppressing in-plane contraction in a tire circumferential direction while ensuring snow column shearing force.SOLUTION: A pneumatic tire is equipped with a shoulder main groove that is disposed on the outermost side in a tire width direction of a plurality of main grooves formed on a tread so as to extend in a tire circumferential direction, and a shoulder lateral groove that extends outward in a tire width direction from the shoulder main groove. The shoulder main groove is equipped with a bottom-up portion raising a groove bottom at an intersecting portion with the shoulder lateral groove. The height of the bottom-up portion is 30% or less of the groove depth of the shoulder main groove.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to pneumatic tires. [Background technology]

[0002] Patent Document 1 below discloses a pneumatic tire that can reduce rolling resistance and noise while maintaining snow traction performance. This pneumatic tire has shoulder main grooves extending in the tire circumferential direction and multiple shoulder lug grooves connected to the shoulder main grooves from the outer sides in the tire width direction, and bottom-raised portions are formed at the groove bottoms of the shoulder main grooves and the shoulder lug grooves.

[0003] When the tread rubber of a pneumatic tire comes into contact with the road surface, it deforms from its curved surface to a flat surface. As a result, an in-plane contraction force acts on the contact surface that is in contact with the road surface from both sides of the tire in the circumferential direction toward the center, causing the tread rubber to deform in the circumferential direction of the tire (in-plane contraction). In-plane contraction leads to a deterioration in ground contact, which tends to deteriorate steering stability and wear performance.

[0004] The pneumatic tire of Patent Document 1 is designed so that there is no bottom-up portion at the intersection of the shoulder main groove and the shoulder lug groove in order to ensure snow column shear force, but this configuration is not effective in suppressing in-plane contraction in the circumferential direction of the tire. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-34698 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide a pneumatic tire that can suppress in-plane contraction in the tire circumferential direction while ensuring snow column shear force. [Means for solving the problem]

[0007] The pneumatic tire of the present disclosure includes a shoulder main groove disposed outermost in a tire width direction among a plurality of main grooves formed in a tread so as to extend along a tire circumferential direction; a shoulder lateral groove extending from the shoulder main groove toward an outer side in the tire width direction, The shoulder main groove has a raised bottom portion at an intersection with the shoulder lateral groove, the raised bottom portion having a raised groove bottom, and the height of the raised bottom portion is 30% or less of the groove depth of the shoulder main groove. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a main part of a pneumatic tire according to an embodiment of the present invention taken along a tire meridian plane; [Figure 2] 1 is a plan view of a pneumatic tire according to an embodiment of the present invention; [Figure 3] Enlarged view of area III in Figure 2 [Figure 4] Enlarged cross-sectional view of the main part taken along line IV-IV in Figure 3. [Figure 5] Enlarged cross-sectional view of the main part of line VV in Figure 3 [Figure 6] FIG. 10 is a partially enlarged view of a pneumatic tire according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, one embodiment of a pneumatic tire will be described with reference to Figures 1 to 5. Note that in each figure, the dimensional ratios in the drawing do not necessarily match the actual dimensional ratios, and the dimensional ratios between the drawings do not necessarily match either.

[0010] In each figure, the first direction D1 is the tire width direction D1, which is parallel to the tire rotation axis, which is the center of rotation of the pneumatic tire (hereinafter also simply referred to as "tire") 1, the second direction D2 is the tire radial direction D2, which is the diameter direction of the tire 1, and the third direction D3 is the tire circumferential direction D3 around the tire rotation axis.

[0011] In the tire width direction D1, the inner side is the side closer to the tire equatorial plane S1, and the outer side is the side farther from the tire equatorial plane S1. In the tire width direction D1, the first side D11 is also referred to as the first width direction side D11, and the second side D12 is also referred to as the second width direction side D12. In addition, in the tire radial direction D2, the inner side is the side closer to the tire rotation axis, and the outer side is the side farther from the tire rotation axis.

[0012] The tire equatorial plane S1 is a plane perpendicular to the tire rotational axis and located at the center in the tire width direction D1 of the tire 1, and the tire meridian plane is a plane including the tire rotational axis and perpendicular to the tire equatorial plane S1. The tire equator line is a line where the outer surface of the tire 1 in the tire radial direction D2 (a tread surface 2a, described later) intersects with the tire equatorial plane S1.

[0013] 1, a tire 1 according to this embodiment includes a pair of beads 1a each having a bead core, sidewalls 1b extending outward in the tire radial direction D2 from each bead 1a, and a tread 2 connected to outer ends of the pair of sidewalls 1b in the tire radial direction D2, the outer surface of which in the tire radial direction D2 comes into contact with the road surface. In this embodiment, the tire 1 is a pneumatic tire 1 filled with air and mounted on a rim 20.

[0014] The tire 1 also includes a carcass 1c that is bridged between a pair of bead cores, and an inner liner 1d that is disposed inside the carcass 1c and has an excellent function of preventing gas permeation in order to maintain air pressure. The carcass 1c and the inner liner 1d are disposed along the inner circumference of the tire, spanning the beads 1a, sidewalls 1b, and tread 2.

[0015] The tread 2 includes a tread rubber 2b having a tread surface 2a that comes into contact with the road surface, and a belt 2c disposed between the tread rubber 2b and the carcass 1c. The tread surface 2a has a contact patch that actually comes into contact with the road surface, and the outer ends of the contact patch in the tire width direction D1 are referred to as contact edges 2d and 2e. The contact patch refers to the tread surface 2a that comes into contact with the road surface when the tire 1 is mounted on a standard rim 20, inflated to the standard internal pressure, placed perpendicularly on a flat road surface, and a standard load is applied.

[0016] The genuine rim 20 is the rim 20 that is defined for each tire 1 by the standard system including the standard on which the tire 1 is based, and is, for example, a standard rim in the case of JATMA, a "Design Rim" in the case of TRA, and a "Measuring Rim" in the case of ETRTO.

[0017] The normal internal pressure is the air pressure specified for each tire 1 by each standard in the standard system including the standard on which tire 1 is based, and is the maximum air pressure in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and "INFLATION PRESSURE" in the case of ETRTO, but if tire 1 is for a passenger car, it is 180 kPa.

[0018] The normal load is the load specified for each tire 1 by each standard in the standard system, including the standard on which tire 1 is based; for JATMA it is the maximum load capacity, for TRA it is the maximum value listed in the table above, and for ETRTO it is the "LOAD CAPACITY." However, if tire 1 is for a passenger car, it shall be 85% of the corresponding load for an internal pressure of 180 kPa.

[0019] As shown in Figures 1 and 2, the tread rubber 2b has a plurality of main grooves 3a, 3b extending in the tire circumferential direction D3. The main grooves 3a, 3b extend continuously in the tire circumferential direction D3. The main grooves 3a, 3b extend in a zigzag pattern with repeated bends. However, the main grooves 3a, 3b may also be configured to extend in a straight line. The number of main grooves 3a, 3b is not particularly limited, but is set to two in this embodiment.

[0020] The main grooves 3a, 3b may have shallower grooves, so-called tread wear indicators (not shown), that become exposed as the grooves wear, allowing the wear level to be determined. The main grooves 3a, 3b may have a groove width that is 3.5% or more of the distance between the ground contact edges 2d, 2e (the dimension in the tire width direction D1). The main grooves 3a, 3b may have a groove width that is 5.0 mm or more.

[0021] Of the multiple main grooves 3a, 3b, the pair of main grooves 3a, 3b located on the outermost sides in the tire width direction D1 are referred to as shoulder main grooves 3a, 3b. When three or more main grooves are provided, the main groove located between the pair of shoulder main grooves 3a, 3b is referred to as the center main groove. The center main groove may extend in a straight or zigzag pattern. Furthermore, intermediate main grooves may be disposed between the center main groove and the shoulder main grooves, providing five or more main grooves. The intermediate main grooves may extend in a straight or zigzag pattern, similar to the center main groove.

[0022] The tread rubber 2b has a plurality of lands 4a to 4c defined by a plurality of main grooves 3a, 3b and a pair of ground contact edges 2d, 2e. The number of lands 4a to 4c is not particularly limited, but is set to three in this embodiment.

[0023] The lands 4a and 4b defined by the shoulder main grooves 3a and 3b and the ground contact edges 2d and 2e are called shoulder lands 4a and 4b, and the land 4c defined by the shoulder main grooves 3a and 3b is called center land 4c.

[0024] The shoulder land 4a has multiple shoulder lateral grooves 51, 52 extending from the shoulder main groove 3a toward the first widthwise side D11. The shoulder lateral groove 51 opens at a bent portion of the shoulder main groove 3a, and the shoulder lateral groove 52 opens at a straight portion of the shoulder main groove 3a. The shoulder land 4a has multiple shoulder blocks 41 divided in the tire circumferential direction D3 by the multiple shoulder lateral grooves 51, 52.

[0025] The shoulder lateral grooves 51, 52 have a groove width of, for example, 4.5 to 8.5 mm. The shoulder lateral grooves 51, 52 have a groove depth of, for example, 7.0 to 12.0 mm. The groove depth of the shoulder lateral grooves 51, 52 is smaller than the groove depth of the shoulder main groove 3a. In this embodiment, the groove depth of the shoulder lateral grooves 51, 52 is 8.5 mm.

[0026] The center land 4c has a plurality of center lateral grooves 61, 62 extending from the shoulder main groove 3a toward the second widthwise side D12. The center lateral grooves 61, 62 both open into the straight portions of the shoulder main grooves 3a. The opening of the center lateral groove 62 into the shoulder main groove 3a faces the opening of the shoulder lateral groove 52 into the shoulder main groove 3a across the shoulder main groove 3a, and the center lateral groove 62 extends so as to be continuous with the shoulder lateral groove 52. The center land 4c has a plurality of center blocks 42 divided in the tire circumferential direction D3 by the plurality of center lateral grooves 61, 62.

[0027] The center lateral grooves 61, 62 have a groove width of, for example, 3.0 to 6.0 mm. The center lateral grooves 61, 62 have a groove depth of, for example, 7.0 to 12.0 mm. The groove depth of the center lateral grooves 61, 62 is smaller than the groove depth of the shoulder main grooves 3a. In this embodiment, the groove depth of the center lateral grooves 61, 62 is 8.5 mm.

[0028] As shown in FIG. 3, the shoulder main groove 3a includes a groove bottom 30, a groove wall 31 on the first widthwise side D11, and a groove wall 32 on the second widthwise side D12.

[0029] The shoulder main groove 3a has a bottom-raised portion 71 at an intersection 33 with the shoulder lateral groove 51. Here, the intersection 33 is the portion where the shoulder main groove 3a and the shoulder lateral groove 51 overlap when it is assumed that the shoulder lateral groove 51 extends to reach the groove wall 32 on the second widthwise side D12 of the shoulder main groove 3a (indicated by a two-dot chain line in FIG. 3).

[0030] The raised bottom portion 71 is formed by raising a part of the groove bottom 30 of the shoulder main groove 3a. The raised bottom portion 71 is raised uniformly as a whole, and the top surface 71a of the raised bottom portion 71 is parallel to the tread surface 2a.

[0031] By providing the raised bottom portion 71 at the intersection 33 between the shoulder main groove 3a and the shoulder lateral groove 51, it is possible to increase the rigidity of the intersection 33, where in-plane contraction force is likely to be large, thereby suppressing in-plane contraction in the tire circumferential direction.

[0032] It is preferable that the raised bottom portions 71 are provided only on a portion of the intersection 33. If the raised bottom portions 71 are provided on the entire intersection 33, the snow column shear force will decrease. It is preferable that the raised bottom portions 71 are provided over 50% or more of the area of ​​the intersection 33. If the raised bottom portions 71 are less than 50% of the area of ​​the intersection 33, it will be difficult to sufficiently suppress in-plane contraction in the tire circumferential direction. It is also preferable that the raised bottom portions 71 are provided over 75% or less of the area of ​​the intersection 33. If the raised bottom portions 71 are more than 75% of the area of ​​the intersection 33, there is a risk that the snow column shear force will decrease.

[0033] The height h71 of the raised bottom portion 71 from the groove bottom 30 (also referred to as the raised bottom height h71) is 30% or less of the groove depth d3 of the shoulder main groove 3a. The height h71 of the raised bottom portion 71 from the groove bottom 30 is preferably 20% or less of the groove depth d3 of the shoulder main groove 3a, and more preferably 15% or less of the groove depth d3 of the shoulder main groove 3a.

[0034] The provision of the raised bottom portion 71 reduces the groove volume of the shoulder main groove 3a, raising concerns about a decrease in snow column shear force, but by setting the raised bottom height h71 of the raised bottom portion 71 to 30% or less of the groove depth d3 of the shoulder main groove 3a, the decrease in snow column shear force can be suppressed. This makes it possible to suppress in-plane contraction in the tire circumferential direction while maintaining snow column shear force.

[0035] The raised height h71 of the raised portion 71 is preferably 10% or more, more preferably 15% or more, of the groove depth d3 of the shoulder main groove 3a. If the raised height h71 of the raised portion 71 is less than 10% of the groove depth d3 of the shoulder main groove 3a, it is difficult to sufficiently suppress in-plane contraction in the tire circumferential direction.

[0036] In this embodiment, the shoulder main groove 3a has a groove depth d3 of 9.5 mm, and the raised portion 71 has a raised height h71 of 1.0 mm, which is approximately 10% of the groove depth d3 of the shoulder main groove 3a.

[0037] The raised bottom portion 71 is provided on the side of the shoulder main groove 3a farther from the shoulder lateral groove 51 (the second widthwise side D12). The raised bottom portion 71 is generally trapezoidal in plan view and has a first side 71b and a second side 71c that face each other and extend along the tire circumferential direction D3. The first side 71b is located on an extension of one groove wall 32 of the shoulder main groove 3a. The second side 71c is located in the groove width direction center of the shoulder main groove 3a. The circumferential length of the raised bottom portion 71 is longest at the second side 71c on the first widthwise side D11 and gradually decreases from the second side 71c toward the first side 71b on the second widthwise side D12. In other words, the circumferential length of the raised bottom portion 71 decreases with increasing distance from the shoulder lateral groove 51.

[0038] The shoulder main groove 3a has a first raised portion 72 that raises the groove bottom 30 so as to be adjacent to the corner of the shoulder block 41. In this embodiment, the height of the first raised portion 72 from the groove bottom 30 of the shoulder main groove 3a is 1.8 mm.

[0039] The shoulder lateral groove 51 includes a second raised portion 73 in contact with the shoulder main groove 3a. In this embodiment, the height of the second raised portion 73 from the groove bottom 30 of the shoulder main groove 3a is 7.5 mm.

[0040] The shoulder lateral groove 51 also includes an inclined portion 731 that extends from the second raised portion 73 toward the first widthwise side D11 while sloping downward. The inclined portion 731 connects the top surface of the second raised portion 73 and the groove bottom of the shoulder lateral groove 51 in an inclined plane.

[0041] The raised bottom portion 71, together with the first raised portion 72 and the second raised portion 73, surrounds a portion of the groove bottom 30 of the shoulder main groove 3a adjacent to the raised bottom portion 71, forming a recess 74. By forming such a recess 74, snow that has entered the shoulder main groove 3a is less likely to escape, thereby ensuring snow column shear force.

[0042] The shoulder main groove 3a has a bottom-raised portion 75 at an intersection 34 with the shoulder lateral groove 52. Here, the intersection 34 is the portion where the shoulder main groove 3a and the shoulder lateral groove 52 overlap when it is assumed that the shoulder lateral groove 52 extends to reach the groove wall 32 on the second widthwise side D12 of the shoulder main groove 3a (shown by a two-dot chain line in FIG. 3).

[0043] The raised bottom portion 75 is formed by raising a part of the groove bottom 30 of the shoulder main groove 3a. The raised bottom portion 75 is raised uniformly as a whole, and the top surface 75a of the raised bottom portion 75 is parallel to the tread surface 2a.

[0044] By providing the raised bottom portion 75 at the intersection 34 between the shoulder main groove 3a and the shoulder lateral groove 52, it is possible to increase the rigidity of the intersection 34, where in-plane contraction force is likely to be large, thereby suppressing in-plane contraction in the tire circumferential direction.

[0045] The bottom raised portion 75 also includes an extension 75d extending into the center lateral groove 62. Providing the extension 75d increases the rigidity of the corners of the center block 42. This further reduces in-plane contraction in the tire circumferential direction.

[0046] It is preferable that the raised bottom portions 75 are provided only on a portion of the intersection 34. If the raised bottom portions 75 are provided on the entire intersection 34, the snow column shear force will decrease. It is preferable that the raised bottom portions 75 are provided over 30% or more of the area of ​​the intersection 34. If the raised bottom portions 75 are less than 30% of the area of ​​the intersection 34, it will be difficult to sufficiently suppress in-plane contraction in the tire circumferential direction. It is also preferable that the raised bottom portions 75% or less of the area of ​​the intersection 34. If the raised bottom portions 75 are more than 75% of the area of ​​the intersection 34, the snow column shear force may decrease.

[0047] The height h75 of the raised bottom portion 75 from the groove bottom 30 (also referred to as the raised bottom height h75) is 30% or less of the groove depth d3 of the shoulder main groove 3a. The height h75 of the raised bottom portion 75 from the groove bottom 30 is preferably 20% or less of the groove depth d3 of the shoulder main groove 3a, and more preferably 15% or less of the groove depth d3 of the shoulder main groove 3a.

[0048] The provision of the raised bottom portion 75 reduces the groove volume of the shoulder main groove 3a, raising concerns about a decrease in snow column shear force, but by setting the raised bottom height h75 of the raised bottom portion 75 to 30% or less of the groove depth d3 of the shoulder main groove 3a, the decrease in snow column shear force can be suppressed. This makes it possible to suppress in-plane contraction in the tire circumferential direction while maintaining snow column shear force.

[0049] The raised height h75 of the raised portion 75 is preferably 10% or more, more preferably 15% or more, of the groove depth d3 of the shoulder main groove 3a. If the raised height h75 of the raised portion 75 is less than 10% of the groove depth d3 of the shoulder main groove 3a, it is difficult to sufficiently suppress in-plane contraction in the tire circumferential direction.

[0050] In this embodiment, the shoulder main groove 3a has a groove depth d3 of 9.5 mm, and the raised portion 75 has a raised height h75 of 1.0 mm, which is approximately 10% of the groove depth d3 of the shoulder main groove 3a.

[0051] The raised bottom portion 75 is provided on the side of the shoulder main groove 3a farther from the shoulder lateral groove 52 (the second widthwise side D12). The raised bottom portion 75 is generally L-shaped in plan view and has a first edge 75b and a second edge 75c that face each other and extend along the tire circumferential direction D3. The first edge 75b is located on the second widthwise side D12, and the second edge 75c is located on the first widthwise side D11. The circumferential length of the raised bottom portion 75 is longest at the second edge 75c on the first widthwise side D11 and gradually decreases from the second edge 75c toward the first edge 75b on the second widthwise side D12. In other words, the circumferential length of the raised bottom portion 75 decreases with increasing distance from the shoulder lateral groove 52.

[0052] The shoulder main groove 3a has a first raised portion 72 that raises the groove bottom 30 so as to be adjacent to the corner of the shoulder block 41. In this embodiment, the height of the first raised portion 72 from the groove bottom 30 of the shoulder main groove 3a is 1.8 mm.

[0053] The shoulder lateral groove 52 includes a second raised portion 73 in contact with the shoulder main groove 3a. In this embodiment, the height of the second raised portion 73 from the groove bottom 30 of the shoulder main groove 3a is 7.5 mm.

[0054] The shoulder lateral groove 52 also includes an inclined portion 731 that extends from the second raised portion 73 toward the first widthwise side D11 while sloping downward. The inclined portion 731 connects the top surface of the second raised portion 73 and the groove bottom of the shoulder lateral groove 52 in an inclined plane.

[0055] The bottom raised portion 75, together with the two first raised portions 72 and the second raised portion 73, surrounds a portion of the groove bottom 30 of the shoulder main groove 3a adjacent to the bottom raised portion 75, forming a recess 76. By forming such a recess 76, snow that has entered the shoulder main groove 3a is less likely to escape, thereby ensuring snow column shear force.

[0056] The center lateral groove 62 has a third raised portion 751 connected to the extended portion 75d of the bottom-raised portion 75. In this embodiment, the height of the third raised portion 751 from the groove bottom 30 of the shoulder main groove 3a is 4 mm.

[0057] As described above, the pneumatic tire 1 of this embodiment comprises, among a plurality of main grooves 3a, 3b formed in the tread 2 to extend along the tire circumferential direction D3, a shoulder main groove 3a that is positioned outermost in the tire width direction D1, and shoulder lateral grooves 51, 52 that extend from the shoulder main groove 3a toward the outside in the tire width direction, and the shoulder main groove 3a has raised bottom portions 71, 75 that raise the groove bottom 30 at the intersections 33, 34 with the shoulder lateral grooves 51, 52, and the heights h71, h75 of the raised bottom portions 71, 75 are 30% or less of the groove depth d3 of the shoulder main groove 3a.

[0058] This configuration increases the rigidity of the intersections 33, 34, where in-plane contraction tends to be large, by providing the raised portions 71, 75 at the intersections 33, 34 of the shoulder main grooves 3a and shoulder lateral grooves 51, 52. Furthermore, by setting the raised heights h71, h75 of the raised portions 71, 75 to 30% or less of the groove depth d3 of the shoulder main grooves 3a, it is possible to suppress a decrease in snow column shear force. As a result, it is possible to suppress in-plane contraction in the tire circumferential direction while maintaining snow column shear force.

[0059] In addition, in the pneumatic tire 1 according to this embodiment, the bottom-raised portions 71, 75 are provided on the side of the shoulder main groove 3a farther from the shoulder lateral grooves 51, 52, and the circumferential length of the bottom-raised portions 71, 75 becomes shorter as they move away from the shoulder lateral grooves 51, 52.

[0060] This configuration can increase the rigidity of the central portion in the groove width direction of the shoulder main groove 3a, where the in-plane contraction force is likely to be large, and therefore can effectively suppress in-plane contraction in the tire circumferential direction.

[0061] Furthermore, in the pneumatic tire 1 according to this embodiment, the bottom raised portions 71, 75 are provided only at a portion of the intersections 33, .

[0062] According to this configuration, the reduction in snow column shear force due to the bottom raising portions 71, 75 can be suppressed.

[0063] In addition, in the pneumatic tire 1 of this embodiment, the bottom-raised portions 71, 75 are configured to surround a portion of the groove bottom 30 of the shoulder main groove 3a adjacent to the bottom-raised portions 71, 75 together with multiple raised portions 72, 73 to form recesses 74, 76.

[0064] By forming the recesses 74, 76, snow that has entered the shoulder main groove 3a is less likely to escape, so that snow column shear force can be secured.

[0065] The pneumatic tire 1 is not limited to the configurations of the above-described embodiments, nor is it limited to the above-described effects. It goes without saying that various modifications can be made to the pneumatic tire 1 without departing from the spirit of the present invention. For example, the configurations and methods of the above-described embodiments may be arbitrarily adopted and combined, and one or more of the configurations and methods of the various modified examples described below may be arbitrarily selected and adopted in the configurations and methods of the above-described embodiments.

[0066] (1) In the pneumatic tire 1 according to the above embodiment, the raised bottom portions 71, 75 are provided on the side of the shoulder main groove 3a farther from the shoulder lateral grooves 51, 52, and the circumferential length of the raised bottom portions 71, 75 decreases with increasing distance from the shoulder lateral grooves 51, 52. However, the pneumatic tire 1 is not limited to this configuration. For example, the raised bottom portions 71, 75 may be provided on the side of the shoulder main groove 3a closer to the shoulder lateral grooves 51, 52, and the circumferential length of the raised bottom portions 71, 75 may be constant in the tire width direction D1.

[0067] (2) In the pneumatic tire 1 according to the above embodiment, the raised bottom portions 71, 75 are provided only in a portion of the intersections 33, 34. However, the pneumatic tire 1 is not limited to this configuration. For example, the raised bottom portions 71, 75 may be provided in the entire intersections 33, 34.

[0068] (3) In the pneumatic tire 1 according to the above embodiment, the raised bottom portions 71, 75, together with the plurality of raised portions 72, 73, surround a portion of the groove bottom 30 of the shoulder main groove 3a adjacent to the raised bottom portions 71, 75, thereby forming recesses 74, 76. However, the pneumatic tire 1 is not limited to this configuration. For example, even if the raised bottom portions 71, 75 do not completely surround the portion of the groove bottom 30 of the shoulder main groove 3a adjacent to the raised bottom portions 71, 75, by providing the raised bottom portions 71, 75, unevenness is formed between the raised bottom portions 71, 75 and the groove bottom 30 of the shoulder main groove 3a adjacent to the raised bottom portions 71, 75, thereby ensuring snow column shear force.

[0069] (4) In the pneumatic tire 1 according to the above embodiment, the raised bottom portions 71, 75 are configured to have a polygonal shape in a plan view. However, the pneumatic tire 1 is not limited to this configuration. For example, the raised bottom portion 77 may be configured with a plurality of ridges extending along the tire circumferential direction D3, as shown in FIG. 6. Furthermore, in the example shown in FIG. 6, the raised bottom portion 77 is provided instead of the raised bottom portion 71, but the raised bottom portion 77 may be provided instead of the raised bottom portion 75. Furthermore, the raised bottom portion 77 may be provided instead of both the raised bottom portion 71 and the raised bottom portion 75.

[0070] (5) In the above embodiment, the shoulder main groove 3a has been described. However, the tire 1 of this embodiment is a tire for which the mounting orientation on a vehicle is not specified, and the shoulder main groove 3b and the shoulder main groove 3a have the same shape. Therefore, it is preferable that the raised bottom portions 71, 75 are also provided in the same shape in both shoulder main grooves 3a, 3b. However, this embodiment can also be applied to a tire with a so-called asymmetric pattern for which the mounting orientation on a vehicle is specified. In such a case, the raised bottom portions 71, 75 may be provided in either the shoulder main groove 3a, 3b, or the shapes of the raised bottom portions 71, 75 may be different in the shoulder main grooves 3a, 3b, or the heights h71, h75 of the raised bottom portions 71, 75 from the groove bottom 30 may be different in the shoulder main grooves 3a, 3b. [Explanation of symbols]

[0071] 1...pneumatic tire, 2...tread, 2a...tread surface, 2d...ground contact edge, 2e...ground contact edge, 3a...main groove (shoulder main groove), 3b...main groove (shoulder main groove), 4a...land (shoulder land), 4b...land (shoulder land), 4c...land (center land), 30...groove bottom of shoulder main groove, 33...intersection of shoulder main groove with shoulder lateral groove, 34...intersection of shoulder main groove with shoulder lateral groove, 41...shoulder block, 42...center block, 51 ...shoulder lateral groove, 52...shoulder lateral groove, 61...center lateral groove, 62...center lateral groove, 71...raised portion, 72...first raised portion, 73...second raised portion, 74...recess, 75...raised portion, 76...recess, 77...raised portion, d3...groove depth of shoulder main groove, h71...raised height, h75...raised height, D1...tire width direction, D11...first side in tire width direction, D12...second side in tire width direction, D2...tire radial direction, D3...tire circumferential direction, S1...tire equatorial plane

Claims

1. Among a plurality of main grooves formed in the tread so as to extend along the tire circumferential direction, shoulder main grooves are arranged on the outermost sides in the tire width direction; a shoulder lateral groove extending from the shoulder main groove toward an outer side in the tire width direction; a center lateral groove extending from the shoulder main groove toward the inside in the tire width direction, an opening of the center lateral groove to the shoulder main groove faces an opening of the shoulder lateral groove to the shoulder main groove across the shoulder main groove; the shoulder main groove has a raised bottom portion at an intersection with the shoulder lateral groove, the raised bottom portion having a raised groove bottom, the height of the raised bottom portion being 30% or less of the groove depth of the shoulder main groove, The pneumatic tire, wherein the bottom raised portion includes an extension portion that extends into the center lateral groove.

2. 2. The pneumatic tire according to claim 1, wherein the raised bottom portion is provided on a side of the shoulder main groove farther from the shoulder lateral groove, and the circumferential length of the raised bottom portion decreases with increasing distance from the shoulder lateral groove.

3. The pneumatic tire according to claim 1 or 2, wherein the raised bottom portion is provided only at a portion of the intersection.

4. The pneumatic tire according to any one of claims 1 to 3, wherein the bottom raised portion, together with a plurality of raised portions, surrounds a part of the groove bottom of the shoulder main groove adjacent to the bottom raised portion to form a recess.

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