Pneumatic tire

Abstract

To provide a pneumatic tire in which durability and grounding property of a shoulder block having a wave-shaped sipe are ensured.SOLUTION: A tread 10 includes a plurality of shoulder blocks 60 which are located on an outermost side in a tire axial direction and are arranged in a tire circumferential direction. The shoulder block 60 has a shape extending in a direction crossing the tire circumferential direction, and has a width direction substantially orthogonal to an extension direction thereof. Further, the shoulder block 60 has at least two shoulder sipes 110 which have a wave shape and extend substantially along the extension direction of the shoulder block 60, and are juxtaposed in the width direction of the shoulder block 60. A ratio of the sum of widths Ws of areas 115 in the plurality of shoulder sipes 110 on a surface of the shoulder block 60 to a width Wb of the shoulder block 60 is 10% or more and 30% or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pneumatic tire.

Background Art

[0002] Conventionally, there is known a pneumatic tire having a tread including a tread surface that contacts the road surface, and a plurality of blocks partitioned by a plurality of grooves extending in the tire circumferential direction and directions intersecting the tire circumferential direction are arranged in the tire circumferential direction, so-called block pattern. Further, a pneumatic tire in which a plurality of sipes are formed in the blocks is known. In this type of tire, the contact pressure on the shoulder blocks arranged in the shoulder regions on both sides in the tire axial direction of the tread may increase. Patent Document 1 discloses a pneumatic tire in which wear of the shoulder blocks can be suppressed by defining the interval between the sipes of the shoulder blocks.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, according to Patent Document 1 above, the interval between the sipes is defined based on the center line of the sipes. Here, among the sipes, there are sipes having a wavy shape when viewed from the tire surface. When the interval between the sipes and the interval between the sipes and the block end are defined based on the center line of the wavy-shaped sipes, those intervals are substantially reduced. In such a case, distortion is likely to occur in the shoulder blocks and the rigidity decreases, resulting in a decrease in durability and a tendency for block chipping in which part or all of the shoulder blocks peel off. Further, the block chipping causes a decrease in the contact performance.

[0005] Therefore, an object of the present invention is to provide a pneumatic tire in which the durability and ground contact performance of a shoulder block having a wave-shaped sipe are ensured.

Means for Solving the Problems

[0006] The pneumatic tire of the present invention is a pneumatic tire including a tread, wherein the tread includes a plurality of shoulder blocks arranged most outward in the tire axial direction and arranged in the tire circumferential direction, and the shoulder block has a shape extending in a direction intersecting the tire circumferential direction and has a width direction substantially orthogonal to the extending direction, and further the shoulder block has a wave shape and extends substantially along the extending direction of the shoulder block, and has at least two shoulder sipings arranged in parallel in the width direction of the shoulder block, and the ratio of the total width of the regions of the plurality of shoulder sipings on the surface of the shoulder block to the width of the shoulder block is 10% or more and 30% or less.

Effects of the Invention

[0007] According to the present invention, it is possible to provide a pneumatic tire in which the durability and ground contact performance of a shoulder block having a wave-shaped sipe are ensured.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 6C

Figure 6D

Figure 7

Figure 8A

Figure 8B

Figure 9A

Figure 9B

Figure 10A

Figure 10B

Figure 11

Figure 12

MODE FOR CARRYING OUT THE INVENTION

[0009] Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is a view showing a part of the outer peripheral surface of a pneumatic tire 1 according to the embodiment in a developed state in a plan view. The tire 1 of the embodiment can be applied to a passenger car tire, but in addition, it can also be applied as a tire for various vehicles such as light trucks, trucks, and buses.

[0010] FIG. 1 shows the tire axial direction X and the tire circumferential direction C. In the tire 1 of the embodiment, the rotational direction during the forward movement of the vehicle to which the tire is mounted is defined on one side of the tire circumferential direction, and the C1 direction shown in FIG. 1 is the rotational direction. Note that, in the following description, the front side refers to the right side in FIG. 1, which is the side of the forward direction of the vehicle corresponding to the tire rotational direction C1, and the rear side refers to the left side in FIG. 1, which is the side of the reverse direction of the vehicle corresponding to the rotational direction C2 opposite to the tire rotational direction C1.

[0011] FIG. 1 shows the tread 10 of the tire 1 and the shoulders 30 on both axial sides of the tread 10. The shoulder 30 is a portion that transitions from the tread 10 to each of the sidewalls (not shown) on both axial sides of the tire and is a portion that contacts the shoulder of the tire 1. The shoulder 30 includes an upper first shoulder 31 in FIG. 1 and a lower second shoulder 32 in FIG. 2.

[0012] (Tread pattern) The tread 10 has a tread surface 20 that contacts the road surface. A tread pattern 11 is formed on the tread surface 20. The tread pattern 11 is mainly formed by a plurality of grooves 12 and a plurality of blocks 13 partitioned by these grooves 12. FIG. 1 shows a tire equator S1, which is a virtual line extending along the tire circumferential direction at the axial center of the tread surface 20.

[0013] When the tire axial direction is the left - right direction, the tread pattern 11 is substantially symmetric about the tire equator S1, except for points slightly displaced in the tire circumferential direction. The tread surface 20 includes a first tread surface 21 on the side of the first shoulder 31 and a second tread surface 22 on the side of the second shoulder 32 with the tire equator S1 as the boundary.

[0014] (Grooves of the tread pattern) The grooves 12 of the tread pattern 11 include a plurality of inclined grooves 40 and a plurality of communication grooves 50. The inclined grooves 40 and the communication grooves 50 of the embodiment are grooves with a groove width exceeding 1 mm.

[0015] The inclined grooves 40 are grooves extending from both sides in the tire axial direction toward the tire equator S1. These inclined grooves 40 are arranged at intervals in the tire circumferential direction. The plurality of inclined grooves 40 include a first inclined groove 41 extending from the first shoulder 31 toward the tire equator S1 and a second inclined groove 42 extending from the second shoulder 32 toward the tire equator S1. The first inclined groove 41 is mainly formed on the first tread surface 21, and the second inclined groove 42 is mainly formed on the second tread surface 22.

[0016] The communication grooves 50 include a first communication groove 51 communicating a pair of adjacent first inclined grooves 41 in the tire circumferential direction and a second communication groove 52 communicating a pair of adjacent second inclined grooves 42 in the tire circumferential direction. The first communication groove 51 is formed on the first tread surface 21, and the second communication groove 52 is formed on the second tread surface 22.

[0017] Since the tread pattern 11 is bilaterally symmetric, the first inclined groove 41 and the second inclined groove 42 have the same mode, and the first communication groove 51 and the second communication groove 52 have the same mode.

[0018] The first inclined groove 41 is a groove that extends forward while gradually curving so that the rear side is convex from the first shoulder 31 toward the tire equator S1, and is inclined with respect to the tire circumferential direction as a whole. The second inclined groove 42 is a groove that extends forward while gradually curving so that the rear side is convex from the second shoulder 32 toward the tire equator S1, and is inclined with respect to the tire circumferential direction as a whole. Here, in each of the inclined grooves 41 and 42, the end on the shoulder 30 (the first shoulder 31, the second shoulder 32) side is the base end, and the end on the tire equator S1 side is the tip end.

[0019] The first inclined groove 41 includes a proximal-side curved portion 43 from the proximal end to around the center in the tire axial direction of the first tread surface 21, and a distal-side curved portion 44 that curves from the end on the tire equator S1 side of the proximal-side curved portion 43 toward the tire equator S1 and reaches the tip. The proximal-side curved portion 43 curves with a relatively small curvature and is slightly inclined forward. The distal-side curved portion 44 curves with the same curvature as the proximal-side curved portion 43 and is inclined forward at a steeper angle than the proximal-side curved portion 43.

[0020] The second inclined groove 42 is also in the same manner as the first inclined groove 41. That is, the second inclined groove 42 includes a proximal-side curved portion 43 from the proximal end to around the center in the tire axial direction of the second tread surface 22, and a distal-side curved portion 44 that curves from the end on the tire equator S1 side of the proximal-side curved portion 43 toward the tire equator S1 and reaches the tip.

[0021] Each of the plurality of first inclined grooves 41 arranged in the tire circumferential direction has a different length alternately. The tip of the shorter first inclined groove 41 terminates in a manner of merging with the second inclined groove 42 immediately before the tire equator S1. The tip of the longer first inclined groove 41 terminates after passing through the tire equator S1 and crossing the distal-side curved portions 44 of two adjacent second inclined grooves 42 in the tire circumferential direction.

[0022] The length of the second inclined groove 42 also differs alternately in the tire circumferential direction in the same manner as the first inclined groove 41. That is, the tip of the shorter second inclined groove 42 terminates in a manner of merging with the first inclined groove 41 immediately before the tire equator S1. The tip of the longer second inclined groove 42 terminates after passing through the tire equator S1 and crossing the distal-side curved portions 44 of two adjacent first inclined grooves 41 in the tire circumferential direction.

[0023] The first communication groove 51 extends straight from the end near the proximal-side curved portion 43 in the distal-side curved portion 44 of the first inclined groove 41 to the vicinity of the bending point where the first inclined groove 41 on the front side in the tire circumferential direction transitions from the proximal-side curved portion 43 to the distal-side curved portion 44.

[0024] The second communication groove 52 is the same as the first communication groove 51, and extends straight from the end near the proximal end side bending portion 43 in the distal end side bending portion 44 of the second inclined groove 42 to the vicinity of the bending point where the second inclined groove 42 on the front side in the tire circumferential direction transitions from the proximal end side bending portion 43 to the distal end side bending portion 44.

[0025] Both the first communication groove 51 and the second communication groove 52 are inclined with respect to the tire circumferential direction so as to face outward in the tire circumferential direction as they extend from the rear side to the front side.

[0026] (Tread pattern block) The blocks 13 of the tread pattern 11 include a plurality of shoulder blocks 60 arranged on the outermost side in the tire axial direction, a plurality of center blocks 70 arranged in the center in the tire axial direction, and a plurality of intermediate blocks 80 arranged between the shoulder blocks 60 and the center blocks 70 in the tire axial direction.

[0027] The shoulder block 60 includes a first shoulder block 61 on the first shoulder 31 side and a second shoulder block 62 on the second shoulder 32 side.

[0028] The first shoulder block 61 is demarcated into a substantially rectangular shape by a pair of first inclined grooves 41 adjacent in the tire circumferential direction and the first communication groove 51. The edge of the first shoulder block 61 on the first shoulder 31 side is continuous with the outer surface of the first shoulder 31. The plurality of first shoulder blocks 61 are arranged in the tire circumferential direction with the proximal end side bending portion 43 of the first inclined groove 41 interposed therebetween.

[0029] The second shoulder block 62 is demarcated into a substantially rectangular shape by a pair of second inclined grooves 42 adjacent in the tire circumferential direction and the second communication groove 52. The edge of the second shoulder block 62 on the second shoulder 32 side is continuous with the outer surface of the second shoulder 32. The plurality of second shoulder blocks 62 are arranged in the tire circumferential direction with the proximal end side bending portion 43 of the second inclined groove 42 interposed therebetween.

[0030] The first shoulder block 61 and the second shoulder block 62, which are arranged in the tire circumferential direction with the base end side curved portion 43 of the inclined groove 40 therebetween, may be arranged at equal intervals in the tire circumferential direction, or may be arranged at variable pitches with unequal intervals. In addition to this, each of the first shoulder block 61 and the second shoulder block 62 may be in a mode of a variable pitch pattern in which the tire circumferential direction length is non-uniform.

[0031] The central block 70 is arranged in a mode straddling both the first tread surface 21 and the second tread surface 22. That is, the tire equator S1 passes through all the central blocks 70. The plurality of central blocks 70 includes a plurality of first central blocks 71 mainly existing on the first tread surface 21 side and a plurality of second central blocks 72 mainly existing on the second tread surface 22 side.

[0032] The proportion of the surface area occupied by the first central block 71 is larger on the first tread surface 21 side than on the second tread surface 22 side. The first central block 71 is demarcated into a substantially rectangular shape by the tip side curved portion 44 of a pair of first inclined grooves 41 adjacent in the tire circumferential direction and the tip side curved portion 44 of the second inclined groove 42 having a larger length among the plurality of second inclined grooves 42.

[0033] The proportion of the surface area occupied by the second central block 72 is larger on the second tread surface 22 side than on the first tread surface 21 side. The second central block 72 is demarcated into a substantially rectangular shape by the tip side curved portion 44 of a pair of second inclined grooves 42 adjacent in the tire circumferential direction and the tip side curved portion 44 of the first inclined groove 41 having a larger length among the plurality of first inclined grooves 41.

[0034] Each of the plurality of first central blocks 71 and the plurality of second central blocks 72 is arranged alternately in the tire circumferential direction.

[0035] The intermediate block 80 includes a first intermediate block 81 on the first tread surface 21 side and a second intermediate block 82 on the second tread surface 22 side.

[0036] The first intermediate block 81 is demarcated into a substantially rectangular shape by the tip-side curved portions 44 of a pair of first inclined grooves 41 adjacent to each other in the tire circumferential direction, the first communication groove 51, and the tip-side curved portion 44 of the second inclined groove 42 having the greater length. A plurality of first intermediate blocks 81 are arranged side by side in the tire circumferential direction with the tip-side curved portions 44 of the first inclined grooves 41 interposed therebetween.

[0037] The second intermediate block 82 is demarcated into a substantially rectangular shape by the tip-side curved portions 44 of a pair of second inclined grooves 42 adjacent to each other in the tire circumferential direction, the second communication groove 52, and the tip-side curved portion 44 of the second inclined groove 42 having the greater length. A plurality of second intermediate blocks 82 are arranged side by side in the tire circumferential direction with the tip-side curved portions 44 of the second inclined grooves 42 interposed therebetween.

[0038] Each of the first intermediate block 81 and the second intermediate block 82 is disposed in the tire axial direction between the shoulder block 60 and the center block 70.

[0039] As described above, the tire equator S1 passes through all the center blocks 70. On the other hand, the tire equator S1 does not pass through the shoulder blocks 60 and the intermediate blocks 80.

[0040] On the first tread surface 21, as a plurality of blocks 13 along the first inclined groove 41, a block row 13A in which three blocks 13 of the first shoulder block 61, the first intermediate block 81, and the first center block 71 extend in this order from the first shoulder 31 side toward the tire equator S1, and a block row 13B in which two blocks 13 of the first shoulder block 61 and the first intermediate block 81 extend in this order are alternately arranged in the tire circumferential direction.

[0041] Similarly, in the second tread surface 22, as a plurality of blocks 13 along the second inclined groove 42, a block row 13A in which three blocks 13 of a second shoulder block 62, a second intermediate block 82, and a second center block 72 extend in this order from the second shoulder 32 side toward the tire equator S1, and a block row 13B in which two blocks 13 of the second shoulder block 62 and the second intermediate block 82 extend in this order are alternately arranged in the tire circumferential direction.

[0042] In both the first tread surface 21 and the second tread surface 22, the intermediate block 80 in the row without the center block 70 has a greater length in the extending direction along the inclined groove 40 than the intermediate block 80 in the row with the center block 70. On the other hand, each of the shoulder block 60 and the center block 70 has an equal length in the extending direction along the inclined groove 40.

[0043] (Block sipe) As shown in FIG. 1, each block 13 of the tread 10 has a plurality of sipes 14. The plurality of sipes 14 include shoulder sip es 110 formed in each of the first shoulder block 61 and the second shoulder block 62 (hereinafter may be collectively referred to as the shoulder block 60), center sip es 120 formed in each of the first center block 71 and the second center block 72 (hereinafter may be collectively referred to as the center block 70), and intermediate sip es 130 formed in each of the first intermediate block 81 and the second intermediate block 82 (hereinafter may be collectively referred to as the intermediate block 80). The groove width of any of the sip es is smaller than that of the above-described inclined groove 40 and communication groove 50, and the groove width is 1 mm or less. The number of sip es 14 per block 13 is arbitrary, but for example, about 2 or more and 5 or less sip es 14 are arranged in one block 13.

[0044] The shoulder sip e 110, the center sip e 120, and the intermediate sip e 130 all open to the surface of each block 60, 70, 80 and have a generally corrugated shape when viewed from the tire surface. The depth direction of each of the sip es 110, 120, 130 is generally along the tire radial direction.

[0045] As shown in FIG. 1, each shoulder block 60 has a plurality of shoulder sipes 110. The shoulder sipes 110 generally extend substantially straight. In each of the shoulder blocks 60, the plurality of shoulder sipes 110 are arranged parallel to each other with a space therebetween. The plurality of shoulder sipes 110 extend substantially parallel to the extending direction of the shoulder block 60 along the inclined groove 40. That is, the shoulder sipes 110 extend in a direction intersecting the tire circumferential direction. The inner end (on the tire equator S1 side) in the tire axial direction of the shoulder sipes 110 communicates with the first communication groove 51 and the second communication groove 52 (hereinafter sometimes collectively referred to as the communication groove 50). The outer end (on the shoulder 30 side) in the tire axial direction of the shoulder sipes 110 terminates without reaching the outer end in the tire axial direction of the shoulder block 60.

[0046] FIG. 2 is a perspective view showing one shoulder sipe 110. FIG. 3A is a view taken along the arrow IIIA-IIIA in FIG. 2. FIG. 3B is a cross-sectional view taken along the arrow IIIB-IIIB in FIG. 2. FIG. 3C is a cross-sectional view taken along the arrow IIIC-IIIC in FIG. 2. FIG. 3D is a cross-sectional view taken along the arrow IIID-IIID in FIG. 2. FIG. 4 is a cross-sectional view taken along the arrow IV-IV in FIG. 3A.

[0047] As shown in FIG. 2, the shoulder sipe 110 has a corrugated portion 113 formed in a corrugated shape along the extending direction, and a sipe bridge 114 that extends straight from one end of the corrugated portion 113 to the communication groove 50 and has a smaller depth than the corrugated portion 113. Further, the shoulder sipe 110 has an opening 113A and a bottom 113B on the surface of the shoulder block 60. The corrugated portion 113 occupies a large part, for example, 70% or more of the extending direction length of the shoulder sipe 110. The depth from the opening 113A to the bottom 113B of the corrugated portion 113 is, for example, about 5.0 mm or more and 7.0 mm or less, and the depth of the sipe bridge 114 is, for example, about 2.0 mm or more and 4.0 mm or less, but is not limited thereto.

[0048] As shown in FIGS. 2 and 3A to 3D, the corrugated portion 113 of the shoulder side 110 is formed in a corrugated shape having a constant period from the opening 113A to the bottom 113B. The amplitude of the corrugated portion 113 is the largest at the opening 113A and the smallest at the bottom 113B. That is, the bottom 113B also has an amplitude and does not have a linear shape. The amplitudes of the openings 113A on the surfaces of the shoulder blocks 60 of the plurality of shoulder sides 110 are the same as each other. Further, the amplitude of the shoulder side 110 decreases at a constant rate from the opening 113A to the bottom 113B. Also, as shown in FIG. 4, the width, which is the gap between the opposing inner surfaces of the shoulder side 110, has a substantially constant dimension from the opening 113A to the bottom 113B. Thereby, as shown in FIG. 4, in a cross-sectional view in the depth direction substantially orthogonal to the extending direction of the shoulder side 110, the shoulder side 110 is linear from the opening 113A to the bottom 113B. The width of the shoulder side 110 is preferably 0.5 mm or more and 1.5 mm or less.

[0049] Note that, as shown in FIGS. 2 and 3B to 3D, the shoulder side 110 of the embodiment has a portion where a part of the corrugated portion 113 is not continuous in the extending direction and a part is missing. This is an exemplary embodiment of the shoulder side 110, and the shoulder side 110 is not limited to this, and a mode in which the corrugated shape is continuous may also be possible.

[0050] As shown in FIG. 1, each central block 70 has a plurality of central sides 120 respectively. The central sides 120 extend straight overall. In each of the plurality of central blocks 70, the plurality of central sides 120 are arranged in parallel with each other at intervals. The plurality of central sides 120 extend substantially parallel to the tire axis direction. That is, the central sides 120 extend in a direction intersecting the tire circumferential direction. Each of both ends of the central side 120 communicates with either the first inclined groove 41 or the second inclined groove 42 (hereinafter sometimes collectively referred to as the inclined groove 40).

[0051] FIG. 5 is a perspective view showing one central groove 120. FIG. 6A is a view taken along line VIA-VIA of FIG. 5. FIG. 6B is a sectional view taken along line VIB-VIB of FIG. 5. FIG. 6C is a sectional view taken along line VIC-VIC of FIG. 5. FIG. 6D is a sectional view taken along line VID-VID of FIG. 5. FIG. 7 is a sectional view taken along line VII-VII of FIG. 6A.

[0052] As shown in FIG. 5, the central groove 120 has a corrugated portion 123 formed in a corrugated shape along the extending direction, a first groove bridge 121 extending straight from one end of the corrugated portion 123 to the inclined groove 40 and having a depth smaller than that of the corrugated portion 123, and a second groove bridge 122 extending straight from the other end of the corrugated portion 123 to the inclined groove 40 and having a depth even smaller than that of the first groove bridge 121. Further, the central groove 120 has an opening 123A and a bottom 123B on the surface of the central block 70. The corrugated portion 123 occupies, for example, 50% or more of the extending direction length of the central groove 120. The depth of the corrugated portion 123 from the opening 123A to the bottom 123B is, for example, about 6.0 mm or more and 7.0 mm or less, the depth of the first groove bridge 121 is, for example, about 4 mm, and the depth of the second groove bridge 122 is, for example, about 2 mm, but is not limited thereto.

[0053] As shown in FIGS. 5 and 6A to 6D, the corrugated portion 123 of the central sipes 120 is formed in a corrugated shape having a constant period from the opening 123A to the bottom 123B. The amplitude of the corrugated portion 123 is the largest at the opening 123A and the smallest at the bottom 123B. That is, the bottom 123B also has an amplitude and does not have a linear shape. The amplitudes of the openings 123A on the surfaces of the central blocks 70 of the plurality of central sipes 120 are the same as each other. Further, the amplitude of the central sipes 120 decreases at a constant rate from the opening 123A to the bottom 123B. Also, as shown in FIG. 7, the width, which is the gap between the opposing inner surfaces of the central sipes 120, has a substantially constant dimension from the opening 123A to the bottom 123B. Thereby, as shown in FIG. 7, in a cross-sectional view in the depth direction substantially orthogonal to the extending direction of the central sipes 120, the central sipes 120 are linear from the opening 123A to the bottom 123B. The width of the central sipes 120 is preferably 0.5 mm or more and 1.5 mm or less.

[0054] As shown in FIG. 1, each intermediate block 80 has a plurality of intermediate sipes 130 respectively. The intermediate sipes 130 extend straight overall. In each of the plurality of intermediate blocks 80, the plurality of intermediate sipes 130 are arranged parallel to each other with an interval therebetween. The plurality of intermediate sipes 130 are all inclined with respect to the tire circumferential direction so as to face the outer side in the tire circumferential direction as they extend from the rear side to the front side. That is, the intermediate sipes 130 extend in a direction intersecting the tire circumferential direction. Each of both ends of the intermediate sipes 130 communicates with either the inclined groove 40 or the communication groove 50.

[0055] The intermediate groove 130 has the same configuration as the above-described central groove 120. That is, although not shown in the drawings, the intermediate groove 130 has portions similar to the corrugated shape portion 123, the first groove bridge 121, and the second groove bridge 122 in the central groove 120, respectively. And the period of the corrugated shape portion of the intermediate groove 130 is constant, and the amplitude is the largest at the opening on the surface of the central block 70 and the smallest at the bottom. The amplitudes of the openings on the surface of the intermediate block 80 of the plurality of intermediate grooves 130 are the same as each other. The width of the intermediate groove 130 is substantially constant from the opening to the bottom. Thereby, in a depth direction cross-sectional view substantially orthogonal to the extending direction of the intermediate groove 130, the intermediate groove 130 is linear from the opening to the bottom. The width of the intermediate groove 130 is preferably 0.5 mm or more and 1.5 mm or less.

[0056] FIG. 8A is a plan view schematically showing the corrugated opening 113A in the shoulder groove 110 and shows the amplitude ShA of the opening 113A. FIG. 8B is a plan view schematically showing the corrugated bottom 113B in the shoulder groove 110 and shows the amplitude ShB of the bottom 113B. FIG. 9A is a plan view schematically showing the corrugated opening 123A in the central groove 120 and shows the amplitude CeA of the opening 123A. FIG. 9B is a plan view schematically showing the corrugated bottom 123B in the central groove 120 and shows the amplitude CeB of the bottom 123B. FIG. 10A is a plan view schematically showing the corrugated opening 133A in the intermediate groove 130 and shows the amplitude MeA of the opening 133A. FIG. 10B is a plan view schematically showing the corrugated bottom 133B in the intermediate groove 130 and shows the amplitude MeB of the bottom 133B.

[0057] In the embodiment, the above amplitudes ShA, CeA, and MeA are not the same, the amplitude ShA of the shoulder groove 110 is the smallest, and the amplitude CeA of the central groove 120 and the amplitude MeA of the intermediate groove 130 are the same as each other or the amplitude CeA of the central groove 120 is larger than the amplitude MeA of the intermediate groove 130. That is, it is defined as "CeA≧MeA>ShA".

[0058] On the condition that 「CeA≧MeA>ShA」, it is preferable that these amplitudes CeA, MeA, and ShA are each not less than 0.5 mm and not more than 1.5 mm.

[0059] Also, it is preferable that the amplitude ShB of the bottom 113B of the shoulder sidewall 110, the amplitude CeB of the bottom 123B of the center sidewall 120, and the amplitude MeB of the bottom 133B of the intermediate sidewall 130 are each not less than 0.1 mm and not more than 0.6 mm.

[0060] Also, when the amplitude of the openings 113A, 123A, and 133A of the respective sidewalls 110, 120, and 130 is A and the amplitude of the bottoms 113B, 123B, and 133B of the respective sidewalls 110, 120, and 130 is B, the ratio A / B of the amplitude A to the amplitude B for each sidewall is preferably not less than 4.0 and not more than 7.0. That is, each of ShA / ShB in the shoulder sidewall 110, CeA / CeB in the center sidewall 120, and MeA / MeB in the intermediate sidewall 130 is preferably not less than 4.0 and not more than 7.0.

[0061] The first shoulder block 61 and the second shoulder block 62 having a plurality of shoulder sidewalls 110 have a substantially rectangular shape extending generally in the tire axial direction. As shown in FIG. 1, the first shoulder block 61 is formed between the base end side curved portions 43 of the first inclined groove 41 adjacent in the tire circumferential direction, and the second shoulder block 62 is formed between the base end side curved portions 43 of the second inclined groove 42 adjacent in the tire circumferential direction. Therefore, the first shoulder block 61 has a shape along the base end side curved portion 43 of the first inclined groove 41, and the second shoulder block 62 has a shape along the base end side curved portion 43 of the second inclined groove 42. That is, each of the first shoulder block 61 and the second shoulder block 62 has a shape in which a rectangle is curved forward with a relatively small curvature with respect to the tire axial direction.

[0062] FIG. 11 is a plan view showing an extract of the first shoulder block 61. FIG. 12 is a view showing an enlarged part of the shoulder side 110. Hereinafter, with reference to FIGS. 11 and 12, the shoulder block 60 including the first shoulder block 61 and the second shoulder block 62 will be described in more detail.

[0063] The shoulder block 60 has a width direction substantially orthogonal to its extending direction. In FIG. 11, the width of the shoulder block 60 is indicated by Wb.

[0064] As shown in FIG. 11, the shoulder block 60 of the embodiment has three shoulder sides 110. Each shoulder side 110 extends substantially along the extending direction of the shoulder block 60, and their extending directions are substantially parallel to each other. Each shoulder side 110 is arranged in parallel at equal intervals in the width direction of the shoulder block 60.

[0065] FIGS. 11 and 12 show the region 115 of the shoulder side 110 on the surface of the shoulder block 60 and the width Ws of this region 115.

[0066] The region 115 of the shoulder side 110 on the surface of the shoulder block 60 referred to here is, as shown in FIG. 12, a region including the width of the entire opening 113A of the corrugated shape portion 113. The width Ws of the region 115 is the dimension in the width direction between the outer edge of the vertex on one side in the width direction of the shoulder side 110 in the opening 113A and the outer edge of the vertex on the other side.

[0067] If the sum of the widths Ws of the regions 115 of the three shoulder sides 110 of one shoulder block 60 is referred to as "3Ws", in the embodiment, the ratio of this 3Ws to the width Wb of the shoulder block 60 is 10% or more and 30% or less.

[0068] Of the three shoulder sipes 110, the distance between the regions 115 of each shoulder sipes 110 at both ends in the width direction of the shoulder block 60 and the end 60a in the width direction of the shoulder block 60 adjacent to these shoulder sipes 110 is equal to the distance G1. The distance G1 is the distance between the end 60a in the width direction of the shoulder block 60 and the region 115 of the shoulder sipes 110 adjacent to this end 60a. Here, if the distance between the regions 115 of adjacent shoulder sipes 110 that are equally spaced is G2, in the embodiment, the distance G1 is larger than the distance G2. As specific dimensions of the distance G1 and the distance G2, on the condition that G1 > G2 is satisfied, for example, it is preferable that the distance G1 is 4 mm or more and the distance G2 is 3 mm or more.

[0069] According to the tire 1 of the above embodiment, the following effects are achieved.

[0070] (1) The tire 1 according to the embodiment includes a tread 10, and the tread 10 includes a block 13 having a sipes 14 extending in a direction intersecting the tire circumferential direction. The sipes 14 extends from the opening to the bottom on the surface of the block 13 and has an amplitude in the waveform shape in the extending direction of the sipes 14. The amplitude is the largest at the opening and the smallest at the bottom, and the amplitude decreases at a constant rate from the opening to the bottom. Thus, in a depth direction cross-sectional view substantially orthogonal to the extending direction of the sipes 14, the sipes 14 is linear from the opening to the bottom. Here, the opening of the sipes referred to here is the opening 113A of the shoulder sipes 110, the opening 123A of the central sipes 120, and the opening 133A of the intermediate sipes 130. Here, the bottom of the sipes referred to here is the bottom 113B of the shoulder sipes 110, the bottom 123B of the central sipes 120, and the bottom 133B of the intermediate sipes 130.

[0071] The bottom of each groove 14 in the embodiment does not have a linear shape along the extending direction of the groove 14, but has an amplitude. When stress is applied to the block 13 on the tread surface 20 during braking or starting of the vehicle, etc., the both side portions of the groove 14 of the block 13 tend to collapse according to the direction in which the stress is applied. At this time, when comparing the case where the bottom of the groove 14 has a linear shape and the case where it has a waveform shape as in the embodiment, the force resisting the stress is higher in the waveform shape. Therefore, the block 13 is less likely to be distorted, and a decrease in the ground contact area of the surface of the block 13 is suppressed. For this reason, the ground contact property is improved. Further, since the distortion of the block 13 is suppressed, a defect such as block chipping in which a part or the whole of the block 13 peels off is suppressed, and thereby the durability of the tire 1 is improved.

[0072] In each groove 14 of the embodiment, the amplitude decreases at a constant rate from the opening to the bottom on the surface of each block 13. Thus, in a depth direction cross-sectional view substantially orthogonal to the extending direction of each groove 14, each groove 14 is linear from the opening to the bottom. Thereby, the starting point of the collapse of the block 13 described above becomes the bottom of the groove 14. Further, since the both side portions of the groove 14 in the block 13 are likely to mesh with each other, the ground contact property is improved. The improvement of the ground contact property leads to the improvement of the cornering characteristics and the handling stability.

[0073] (2) In the tire 1 of the above (1) according to the embodiment, it is preferable that the amplitude of the opening on the surface of the block 13 of the groove 14 is 0.5 mm or more and 1.5 mm or less.

[0074] Thereby, the above-described effects can be easily obtained.

[0075] (3) In the tire 1 of the above (1) and (2) according to the embodiment, it is preferable that the amplitude of the bottom of the groove 14 is 0.1 mm or more and 0.6 mm or less.

[0076] Thereby, the above-described effects can be easily obtained.

[0077] (4) In the tire 1 according to the above (1) to (3) embodiments, the width of the sipe 14 is preferably 0.5 mm or more and 1.5 mm or less.

[0078] Thereby, the above-described effects can be easily obtained.

[0079] (5) In the tire 1 according to the above (1) to (4) embodiments, the ratio As / Ab of the amplitude As of the opening on the surface of the block 13 of the sipe 14 to the amplitude Ab at the bottom of the sipe 14 is preferably 4.0 or more and 7.0 or less.

[0080] Thereby, the above-described effects can be easily obtained.

[0081] (6) The tire 1 according to the embodiment includes a tread 10. The tread 10 is arranged on the outermost side in the tire axial direction and includes a plurality of shoulder blocks 60 arranged in the tire circumferential direction. The shoulder block 60 has a shape extending in a direction intersecting the tire circumferential direction and has a width direction substantially orthogonal to the extending direction. Further, the shoulder block 60 has a corrugated shape and extends substantially along the extending direction of the shoulder block 60, and has at least two shoulder sipes 110 arranged in parallel in the width direction of the shoulder block 60. The ratio of the total width Ws of the regions 115 of the plurality of shoulder sipes 110 on the surface of the shoulder block 60 to the width Wb of the shoulder block 60 is 10% or more and 30% or less.

[0082] Generally, when a plurality of sipes are formed in a block, the grip performance of the tire due to the edge effect is improved. On the contrary, if the area occupied by the sipe is large, the rigidity of the block decreases. In this regard, when the ratio of the total width Ws of the regions 115 of the plurality of shoulder sipes 110 on the surface of the shoulder block 60 to the width Wb of the shoulder block 60 is 10% or more and 30% or less as in the embodiment, distortion hardly occurs in the shoulder block 60, the decrease in the rigidity of the shoulder block 60 is suppressed, and the grip performance by the shoulder sipe 110 is ensured.

[0083] In an embodiment, the shoulder side portion 110 has a corrugated shape, and the region occupied by the shoulder side portion 110 is defined as a region 115 corresponding to the overall width Ws of the corrugated shape portion 113, rather than the width of the opening 113A of the shoulder side portion 110. Therefore, based on the width Ws of the region 115, by defining the ratio of the total width Ws of the regions 115 of the plurality (three) of shoulder side portions 110 to the width Wb of the shoulder block 60 to be 10% or more and 30% or less, a decrease in the rigidity of the shoulder block 60 can be suppressed.

[0084] Thus, in the tire 1 of the embodiment, since a decrease in the rigidity of the shoulder block 60 is suppressed, chipping of the shoulder block 60 is suppressed, and as a result, durability and ground contact performance are ensured.

[0085] (7) In the tire 1 according to the above (6) of the embodiment, it is preferable that the distance G1 between the end 60a in the width direction of the shoulder block 60 and the region 115 of the shoulder side portion 110 adjacent to the end 60a is larger than the distance G2 between the regions 115 of a pair of shoulder side portions 110 adjacent in the circumferential direction.

[0086] The vicinity of the end 60a in the width direction of the shoulder block 60 is likely to have a decrease in rigidity. However, as in the embodiment, by making the distance G1 between the end 60a in the width direction of the shoulder block 60 and the region 115 of the shoulder side portion 110 adjacent to the end 60a larger than the distance G2 between the regions 115 of a pair of shoulder side portions 110 adjacent in the circumferential direction, a decrease in the rigidity in the vicinity of the end 60a can be suppressed. For this reason, chipping in the vicinity of the end 60a in the width direction of the shoulder block 60 is suppressed, and as a result, durability and ground contact performance are ensured.

[0087] (8) In the tire 1 according to the above (7) of the embodiment, it is preferable that the distance G2 is 3 mm or more and the distance G1 is 4 mm or more.

[0088] As a result, block chipping near the widthwise end 60a of the shoulder block 60 is suppressed, and as a result, durability and ground contact performance are ensured.

[0089] (9) In the tire 1 according to the above (6) to (8) embodiments, the tire circumferential lengths of the plurality of shoulder blocks 60 include cases where they are non-uniform.

[0090] As a result, the tire circumferential lengths of the plurality of shoulder blocks 60 are non-uniform, that is, the durability and ground contact performance of the shoulder blocks 60 with a variable pitch pattern are ensured.

[0091] Note that the present invention is not limited to the above embodiments, and modifications, improvements, etc. may be made within the scope that can achieve the object of the present invention, and they are included in the scope of the present invention.

[0092] For example, the corrugated shape portion of each cycle may have a corrugated shape such as the period of a trigonometric function, or may have a corrugated shape in which only the apex portion has a relatively large curvature R shape and the portions between the apexes are straight lines. The curvature radius of the R at the apex or the R portion where the cycle bridge transitions to the corrugated shape portion is arbitrary, but may be about 0.6 mm, for example.

[0093] The shoulder block 60 of the embodiment has three shoulder cycles 110, but the number of shoulder cycles 110 is not limited to this, and for example, it may have 2 to 5 or more shoulder cycles 110.

Explanation of Reference Numerals

[0094] 1... Tire (pneumatic tire) 10... Tread 13... Block 60... Shoulder block 110... Shoulder cycle G1... Distance between the widthwise end of the shoulder block and the region of the shoulder cycle G2... Distance between the regions of adjacent shoulder cycles Wb... Width of the shoulder block Ws…Width of the region of the shoulder side

Claims

**Claim 1** A pneumatic tire having a tread, wherein the tread includes a plurality of shoulder blocks arranged on the outermost side in the tire axial direction and aligned in the tire circumferential direction, the shoulder block has a shape extending in a direction intersecting the tire circumferential direction and has a width direction substantially orthogonal to the extending direction, furthermore, the shoulder block has a corrugated shape and extends substantially along the extending direction of the shoulder block, and has at least two shoulder sipes arranged in parallel in the width direction of the shoulder block, a pneumatic tire in which a ratio of a total width of regions of the plurality of shoulder sipes on a surface of the shoulder block to a width of the shoulder block is 10% or more and 30% or less. **Claim 2** The pneumatic tire according to claim 1, wherein a distance G1 between an end in the width direction of the shoulder block and a region of the shoulder sipes adjacent to the end is larger than a distance G2 between regions of a pair of adjacent shoulder sipes in the parallel direction. **Claim 3** The pneumatic tire according to claim 2, wherein the distance G2 is 3 mm or more and the distance G1 is 4 mm or more. **Claim 4** The pneumatic tire according to any one of claims 1 to 3, wherein a tire circumferential direction length of the plurality of shoulder blocks is non-uniform.

Images