Pneumatic tires

Abstract

To provide a pneumatic tire that can be improved in traction performance and uneven wear resistance performance (tow-and-heel wear resistance performance).SOLUTION: The pneumatic tire comprises a plurality of main grooves formed at a tread and extended along a tire circumferential direction. The plurality of main grooves include shoulder main grooves positioned at an outermost side in a tire width direction. The shoulder main groove comprises a raised part in which a first side in the tire width direction of a groove bottom of the shoulder main grooves is raised upper than a second side thereof, where the raised part is lower than an outer surface of the tread and extends continuously over the whole circumference in the tire circumferential direction.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] The following Patent Document 1 discloses a pneumatic tire having a main groove (hereinafter referred to as shoulder main groove) located at the outermost side of the ground contact surface in the tire width direction and extending in the tire circumferential direction, a lug groove extending from the shoulder main groove to the outer side of the tire ground contact edge, and a bottom-raised portion that is provided across the shoulder main groove and the lug groove including the boundary portion leading from the lug groove to the shoulder main groove and that raises the groove bottom. By providing the bottom-raised portion, it is possible to improve the rigidity of the corners of the blocks in the shoulder portion where deformation is likely to occur. However, since the bottom-raised portion is intermittently arranged together with the lug groove in the tire circumferential direction, it hardly contributes to improving the traction performance. In addition, since the bottom-raised portion is intermittently arranged, the rigidity of the corners of the blocks is insufficient, and there is room for improvement in uneven wear resistance, especially in toe-heel wear resistance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-147598 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide a pneumatic tire that can improve traction performance and uneven wear resistance (toe-heel wear resistance). [Means for solving the problem]

[0005] The pneumatic tire of the present disclosure includes a plurality of main grooves formed in a tread and extending along a tire circumferential direction, The plurality of main grooves include a shoulder main groove located outermost in a tire width direction, The shoulder main groove has a raised portion in which a first side of a groove bottom of the shoulder main groove in a tire width direction is raised higher than a second side of the groove bottom, The raised portion is lower than an outer surface of the tread and extends continuously around the entire circumference in the tire circumferential direction. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a cross-sectional view of a main portion of a pneumatic tire according to an embodiment of the present invention taken along a tire meridian plane. [Diagram 2] FIG. 1 is a front view of a pneumatic tire according to an embodiment of the present invention; [Diagram 3] Enlarged view of area III in Fig. 2 [Figure 4] Enlarged cross-sectional view of the main part taken along line IV-IV in Figure 3. [Diagram 5] Enlarged cross-sectional view of the main part of the VV line in Figure 3 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] 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.

[0008] 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 a 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.

[0009] 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 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.

[0010] The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis and located at the center in the tire width direction D1 of the tire 1, and the tire meridian plane is a plane that includes the tire rotation axis and is perpendicular to the tire equatorial plane S1. The tire equatorial line is a line where the outer surface of the tire 1 in the tire radial direction D2 (a tread surface 2a described later) and the tire equatorial plane S1 intersect.

[0011] 1, a tire 1 according to this embodiment includes a pair of beads 1a each having a bead core, sidewalls 1b each extending outward in a 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 a road surface. In this embodiment, the tire 1 is a pneumatic tire 1 in which air is put, and is mounted on a rim 20.

[0012] 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, the sidewalls 1b, and the tread 2.

[0013] 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 surface that actually comes into contact with the road surface, and the outer ends of the contact surface in the tire width direction D1 are called contact ends 2d, 2e. The contact surface 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 a standard internal pressure, placed vertically on a flat road surface, and a standard load is applied.

[0014] The genuine rim 20 is a rim 20 that is defined for each tire 1 by a standard system including the standard on which the tire 1 is based, 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.

[0015] The normal internal pressure is the air pressure set 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 passenger cars, it is 180 kPa.

[0016] The normal load is the load determined 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 shown in the table above, and for ETRTO, it is the "LOAD CAPACITY." However, if tire 1 is for passenger cars, it is 85% of the corresponding load at an internal pressure of 180 kPa.

[0017] 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 shape with repeated bending. The number of main grooves 3a, 3b is not particularly limited, but is set to two in this embodiment.

[0018] The main grooves 3a, 3b may have a shallow portion, a so-called tread wear indicator (not shown), which becomes exposed as the grooves wear, to indicate the degree of wear. For example, the main grooves 3a, 3b may have a groove width of 3% or more of the distance between the ground contact ends 2d, 2e (the dimension in the tire width direction D1). For example, the main grooves 3a, 3b may have a groove width of 5 mm or more.

[0019] Among the main grooves 3a, 3b, a pair of main grooves 3a, 3b arranged on the outermost sides in the tire width direction D1 are called shoulder main grooves 3a, 3b. When three or more main grooves are provided, the main groove arranged between the pair of shoulder main grooves 3a, 3b is called a center main groove. The center main groove may extend in a straight or zigzag shape.

[0020] The tread rubber 2b has a plurality of lands 4a-4c defined by a plurality of main grooves 3a, 3b and a pair of ground contact edges 2d, 2e. The number of the lands 4a-4c is not particularly limited, but is three in this embodiment.

[0021] The lands 4a, 4b defined by the shoulder main grooves 3a, 3b and the ground contact edges 2d, 2e are called shoulder lands 4a, 4b, and the land 4c defined by the shoulder main grooves 3a, 3b is called center land 4c.

[0022] The shoulder land 4a includes a plurality of lateral grooves 5 extending from the shoulder main groove 3a toward the first widthwise side D11. The lateral grooves 5 open into the shoulder main groove 3a. The shoulder land 4a includes a plurality of shoulder blocks 40 divided in the tire circumferential direction D3 by the plurality of lateral grooves 5.

[0023] The lateral groove 5 has a first portion 5a extending in a direction inclined with respect to the tire width direction D1 and a second portion 5b extending parallel to the tire width direction D1. The groove width of the lateral groove 5 is, for example, 3.8 to 6.6 mm. The groove depth of the lateral groove 5 is, for example, 8.9 to 9.7 mm.

[0024] The shoulder land 4a includes a sipe 51. The sipe 51 extends parallel to the first portion 5a of the lateral groove 5. One end of the sipe 51 opens into the shoulder main groove 3a, and the other end terminates in the shoulder block 40. The shoulder land 4a includes a width groove 52. The width groove 52 extends along the tire width direction D1. In this specification, the term "sipe" refers to a groove having a width dimension of less than 1.6 mm on the tread surface 2a. In this specification, "parallel" includes not only completely parallel but also approximately parallel with an intersection angle of 5 degrees or less (hereinafter the same).

[0025] The shoulder main groove 3a includes a groove bottom 30, a groove wall 31 on a first widthwise side D11, and a groove wall 32 on a second widthwise side D12.

[0026] The groove wall 32 on the second widthwise side D12 extends in a zigzag shape along the tire circumferential direction D3. On the other hand, the groove wall 31 on the first widthwise side D11 includes a bent portion 311 that bends and extends parallel to the opposing groove wall 32, and a flat portion 312 that extends parallel to the tire circumferential direction D3. The bent portion 311 and the flat portion 312 are disposed adjacent to each other. The groove wall 31 including the flat portion 312 provides better resistance to uneven wear (resistance to toe-heel wear) than a case in which the groove wall 31 is entirely zigzag like the groove wall 32.

[0027] The length L2 of the flat portion 312 is preferably 50% or more of the total length L1+L2 of the length L1 of the bent portion 311 and the length L2 of the flat portion 312 (see FIG. 2). By making the length L2 50% or more of the length L1+L2, the uneven wear resistance is improved. Here, the lengths L1 and L2 are lengths in the tire circumferential direction D3.

[0028] The shoulder main groove 3a has a raised portion 6 in which the first widthwise side D11 of the groove bottom 30 is raised higher than the second widthwise side D12. The raised portion 6 extends continuously around the entire circumference in the tire circumferential direction D3. The raised portion 6 has a top surface 61 parallel to the tread surface 2a and an outer side surface 62 parallel to the groove wall 31. The groove wall 31 is an exposed wall surface on the outer side of the raised portion 6 in the tire radial direction D2.

[0029] As shown in FIG. 4, the top surface 61 of the raised portion 6 is lower than the tread surface 2a. The depth d6 from the tread surface 2a to the top surface 61 is, for example, 6.0 to 7.0 mm. The depth d6 is constant throughout the raised portion 6, but is not limited thereto. By providing the raised portion 6 in the shoulder main groove 3a, the step of the raised portion 6 can improve the traction performance. In addition, by providing the raised portion 6 continuously around the entire circumference, the traction performance can be further improved. Furthermore, by providing the raised portion 6, the rigidity of the shoulder block 40 adjacent to the raised portion 6 can be increased and deformation of the main groove surface shape can be suppressed. This can suppress toe-heel wear of the shoulder block 40.

[0030] The height h6 of the raised portion 6 from the groove bottom 30 is preferably 10 to 50% of the groove depth d3 of the shoulder main groove 3a. By setting the height h6 of the raised portion 6 in this range, it is possible to improve traction performance and uneven wear resistance while preventing deterioration of the drainage performance of the shoulder main groove 3a.

[0031] The outer surface 62 of the second width direction side D12 of the raised portion 6 extends in a zigzag shape along the tire circumferential direction D3. The outer surface 62 also extends in a curved shape so as to be parallel to the groove wall 32 of the opposing shoulder main groove 3a. By making the outer surface 62 zigzag, the curved edge of the outer surface 62 can improve traction performance.

[0032] A first bent point 62a of the outer surface 62 convex toward the first widthwise side D11 is adjacent to the opening of the lateral groove 5 in the tire width direction D1. A second bent point 62b of the outer surface 62 convex toward the second widthwise side D12 faces the flat portion 312 of the shoulder main groove 3a in the tire width direction D1.

[0033] The raised portion 6 includes an extension portion 63 extending into the lateral groove 5. The depth from the tread surface 2a to the top surface of the extension portion 63 is the same as the depth d6 from the tread surface 2a to the top surface 61 of the raised portion 6. The width of the extension portion 63 is the same as the groove width of the lateral groove 5. The extension portion 63 extends to the middle of the first portion 5a of the lateral groove 5. The ends 63a of the multiple extension portions 63 are disposed at the same position in the tire width direction D1 and are aligned in a straight line in the tire circumferential direction D3.

[0034] The extension portion 63 has sipes 7 extending along the extension direction of the lateral grooves 5. One end of the sipes 7 opens into the shoulder main groove 3a, and the other end terminates within the extension portion 63. Therefore, the raised portion 6 is continuous in the tire circumferential direction D3 without being interrupted by the sipes 7. The sipes 7 are disposed at the width center of the extension portion 63. By providing the sipes 7 in the extension portion 63, it is possible to prevent the corners of the shoulder blocks 40 from becoming too rigid due to the extension portion 63, and to suppress deterioration of ground contact.

[0035] The groove depth d7 of the sipe 7 is shallower than the groove depth d3 of the shoulder main groove 3a. If the sipe 7 is too deep, it may cause cracks. The sipe 7 of this embodiment has a groove width of 0.8 mm and a groove depth of 8.0 to 8.5 mm.

[0036] 2, the center land 4c includes a plurality of circumferential grooves 81 extending along the tire circumferential direction D3, a plurality of width grooves 82 extending along the tire width direction D1, and a plurality of sipes 83. The circumferential grooves 81 and the width grooves 82 intersect with each other.

[0037] As described above, the pneumatic tire 1 according to this embodiment includes a plurality of main grooves 3a, 3b formed in the tread 2 and extending along the tire circumferential direction D3, The main grooves 3a, 3b include a shoulder main groove 3a located at the outermost side in the tire width direction D1, The shoulder main groove 3a has a raised portion 6 in which a first side D11 in the tire width direction D1 of a groove bottom 30 of the shoulder main groove 3a is raised higher than a second side D12, The raised portion 6 is lower than the outer surface 2a of the tread 2 and extends continuously over the entire circumference in the tire circumferential direction D3.

[0038] According to this configuration, by providing the raised portion 6 in the shoulder main groove 3a, the step of the raised portion 6 can improve traction performance. Also, by providing the raised portion 6 continuously around the entire circumference, traction performance can be further improved. Furthermore, by providing the raised portion 6 continuously around the entire circumference, the rigidity of the shoulder block 40 adjacent to the raised portion 6 can be sufficiently increased, and uneven wear resistance (toe-heel wear resistance) can be improved.

[0039] In the pneumatic tire 1 according to this embodiment, the outer surface 62 of the raised portion 6 on the second side D12 in the tire width direction extends in a zigzag shape along the tire circumferential direction D3.

[0040] According to this configuration, by forming the outer surface 62 in a zigzag shape, the curved edges of the outer surface 62 can improve traction performance.

[0041] In addition, in the pneumatic tire 1 of this embodiment, the groove wall 32 on the tire width direction second side D12 of the shoulder main groove 3a extends in a zigzag pattern along the tire circumferential direction D3, and the groove wall 31 on the tire width direction first side D11 of the shoulder main groove 3a includes a flat portion 312 extending parallel to the tire circumferential direction D3.

[0042] According to this configuration, the resistance to uneven wear is improved compared to a case in which both groove walls 31, 32 are formed in a zigzag shape.

[0043] In the pneumatic tire 1 according to this embodiment, the tire width direction first side D11 is configured to be on the outer side in the tire width direction D1.

[0044] According to this configuration, it is possible to suppress toe-heel wear of the shoulder blocks 40 located on the outer side of the shoulder main grooves 3a in the tire width direction D1.

[0045] In addition, in the pneumatic tire 1 of this embodiment, the shoulder land 4a defined by the shoulder main groove 3a and the ground contact edge 2d has a plurality of lateral grooves 5 extending from the shoulder main groove 3a toward the first side D11 in the tire width direction, the raised portion 6 has an extension portion 63 extending into the lateral grooves 5, and the extension portion 63 has a sipe 7 extending along the extension direction of the lateral grooves 5.

[0046] This configuration makes it possible to suppress deterioration of ground contact caused by the extension portion 63, and also ensure traction at the bottom of the groove and drainage after wear.

[0047] The pneumatic tire 1 is not limited to the configurations of the above-described embodiments, and is not limited to the above-described effects. Of course, the pneumatic tire 1 can be modified in various ways 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.

[0048] (1) In the pneumatic tire 1 according to the above embodiment, the outer surface 62 of the raised portion 6 on the second side D12 in the tire width direction extends in a zigzag shape along the tire circumferential direction D3. However, the pneumatic tire 1 is not limited to this configuration. For example, even if the outer surface 62 of the raised portion 6 extends linearly in the tire circumferential direction D3, it is possible to improve the traction performance and uneven wear resistance.

[0049] (2) In the pneumatic tire 1 according to the above embodiment, the groove wall 32 on the second side D12 in the tire width direction of the shoulder main groove 3a extends in a zigzag manner along the tire circumferential direction D3, and the groove wall 31 on the first side D11 in the tire width direction of the shoulder main groove 3a includes a flat portion 312 extending parallel to the tire circumferential direction D3. However, the pneumatic tire 1 is not limited to this configuration. For example, the groove wall 31 on the first side D11 in the tire width direction of the shoulder main groove 3a may not include the flat portion 312 and may extend in a zigzag manner along the tire circumferential direction D3 like the groove wall 32 on the second side D12 in the tire width direction. In addition, the groove wall 31 on the first side D11 in the tire width direction of the shoulder main groove 3a may not include the bent portion 311 and may extend parallel to the tire circumferential direction D3 as a whole.

[0050] (3) In the pneumatic tire 1 according to the above embodiment, the first side D11 in the tire width direction is configured to be on the outer side in the tire width direction D1. However, the pneumatic tire 1 is not limited to such a configuration. For example, the first side D11 in the tire width direction may be on the inner side in the tire width direction D1. In other words, the raised portion 6 may be provided adjacent to the center land 4c.

[0051] (4) In the pneumatic tire 1 according to the above embodiment, the shoulder land 4a defined by the shoulder main groove 3a and the ground contact edge 2d includes a plurality of lateral grooves 5 extending from the shoulder main groove 3a toward the first side D11 in the tire width direction, the raised portion 6 includes an extension portion 63 extending into the lateral groove 5, and the extension portion 63 includes a sipe 7 extending along the direction in which the lateral groove 5 extends. However, the pneumatic tire 1 is not limited to such a configuration. For example, the extension portion 63 does not need to include the sipe 7, and further the extension portion 63 itself does not need to be provided.

[0052] (5) In the above embodiment, the shoulder main groove 3a has been described, but the tire 1 of this embodiment is a tire for which the mounting direction on the 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 portion 6 is also provided in the same shape in both the shoulder main grooves 3a and 3b. However, this embodiment is also applicable to a tire having a so-called asymmetric pattern in which the mounting direction on the vehicle is specified, and in that case, the raised portion 6 may be provided in either the shoulder main groove 3a or 3b, or the shape of the raised portion 6 may be different between the shoulder main grooves 3a and 3b, or the depth d6 from the tread surface 2a to the top surface 61 may be different between the shoulder main grooves 3a and 3b. [Explanation of symbols]

[0053] Reference Signs List 1...pneumatic tire, 2...tread, 2a...tread surface, 2d...ground edge, 2e...ground 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), 5...lateral groove, 6...raised portion, 7...sipe, 30...groove bottom, 31...groove wall, 32...groove wall, 40...shoulder block, 61...top surface of raised portion, 62...outer surface of raised portion, 63...extension, 311...bent portion, 312...flat portion, D1...tire width direction, D11...tire width direction first side, D12...tire width direction second side, D2...tire radial direction, D3...tire circumferential direction, S1...tire equatorial surface

Claims

1. The tire has a plurality of main grooves formed in the tread and extending in a circumferential direction of the tire, The plurality of main grooves include a shoulder main groove located outermost in a tire width direction, The shoulder main groove includes a raised portion in which a first side of a groove bottom of the shoulder main groove in a tire width direction is raised higher than a second side of the groove bottom, The raised portion is lower than an outer surface of the tread and extends continuously around the entire circumference in the tire circumferential direction, A shoulder land defined by the shoulder main groove and a ground contact edge includes a plurality of lateral grooves extending from the shoulder main groove toward a first side in a tire width direction, The raised portion includes an extension portion extending into the lateral groove, The extension portion includes a sipe extending along a direction in which the lateral groove extends.

2. The pneumatic tire according to claim 1 , wherein an outer surface of the raised portion on a second side in the tire width direction extends in a zigzag shape along the tire circumferential direction.

3. A groove wall of the shoulder main groove on a second side in the tire width direction extends in a zigzag shape along the tire circumferential direction, The pneumatic tire according to claim 1 , wherein a groove wall of the shoulder main groove on a first side in the tire width direction includes a flat portion extending parallel to a tire circumferential direction.

4. The pneumatic tire according to any one of claims 1 to 3, wherein the first side in the tire width direction is an outer side in the tire width direction.

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