Pneumatic tire

Abstract

To provide a pneumatic tire in which a block arranged in a shoulder region is hardly damaged so that traveling stability can be secured on a snow-covered road surface.SOLUTION: In a pneumatic tire: a shoulder block 60 includes at least one shoulder siping 110 which has wavy shapes when viewing a tire surface and extends in a direction crossing a tire circumferential direction; a center block 70 includes at least one center siping 120 which has wavy shapes when view the tire surface and extends in the direction crossing the tire circumferential direction; an intermediate block 80 includes at least one intermediate siping 130 which has wavy shapes when view the tire surface and extends in the direction crossing the tire circumferential direction; and CeA≥MeA>ShA is satisfied where ShA is amplitude of the shoulder siping 110 on the tire surface, CeA is amplitude of the center siping 120 on the tire surface, and MeA is amplitude of the intermediate siping 130 on the tire surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, there is known a tire having a tread including a tread surface that contacts the road surface, and a so-called block pattern in which a plurality of blocks partitioned by a plurality of grooves extending in the tire circumferential direction or in a direction intersecting the tire circumferential direction are arranged in the tire circumferential direction. Patent Document 1 discloses a pneumatic tire in which a plurality of sipes having a wave shape when viewed from the tire surface are formed in such blocks. For example, wave-shaped sipes having a large amplitude are considered to be effective in improving tire grip performance when traveling on snowy roads. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-310013 Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of tire, the ground pressure on the blocks arranged in the shoulder regions on both sides of the tread in the tire axial direction tends to be large, and in particular, the area around the sipes, which have a wave-shaped shape with a large amplitude, is likely to receive high pressure. This can lead to problems such as local wear around the sipes and block chipping, and there is room for improvement. In addition, the shoulder blocks in particular have a large impact on driving stability on snowy roads.

[0005] An object of the present invention is to provide a pneumatic tire in which blocks arranged in the shoulder region are also less likely to be damaged and driving stability on snow-covered roads can be ensured. [Means for solving the problem]

[0006] The pneumatic tire of the present invention is a pneumatic tire having a tread, the tread including a plurality of blocks arranged in a tire circumferential direction, the plurality of blocks including a plurality of shoulder blocks arranged outermost in the tire axial direction, a plurality of central blocks arranged in the center in the tire axial direction, and a plurality of intermediate blocks arranged between the shoulder blocks and the central blocks in the tire axial direction, the shoulder blocks having at least one shoulder sipe having a wave-shaped shape as seen on the tire surface and extending in a direction intersecting the tire circumferential direction, the central blocks having at least one central sipe having a wave-shaped shape as seen on the tire surface and extending in a direction intersecting the tire circumferential direction, the intermediate blocks having at least one intermediate sipe having a wave-shaped shape as seen on the tire surface and extending in a direction intersecting the tire circumferential direction, and where ShA is the amplitude of the shoulder sipe on the tire surface, CeA is the amplitude of the central sipe on the tire surface, and MeA is the amplitude of the intermediate sipe on the tire surface, CeA≧MeA>ShA. Effect of the Invention

[0007] According to the present invention, it is possible to provide a pneumatic tire in which blocks arranged in the shoulder region are also less susceptible to damage and driving stability on snow-covered roads can be ensured. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a tread pattern of a pneumatic tire according to an embodiment, and is a partial development view of an outer circumferential surface of the tire. [Diagram 2] FIG. 2 is a perspective view showing a shoulder sipe according to an embodiment. [Figure 3A] FIG. 3 is a view taken along the line IIIA-IIIA in FIG. 2. [Figure 3B] FIG. 3 is a cross-sectional view taken along line IIIB-IIIB of FIG. 2. [Figure 3C] FIG. 3 is a cross-sectional view taken along line IIIC-IIIC of FIG. 2. [Figure 3D]FIG. 3 is a cross-sectional view taken along line IIID-IIID in FIG. 2 . [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 3A. [Diagram 5] FIG. 2 is a perspective view showing a central sipe according to an embodiment. [Figure 6A] FIG. 6 is a view taken along the VIA-VIA arrows in FIG. 5. [Figure 6B] FIG. 6 is a cross-sectional view taken along line VIB-VIB of FIG. 5. [Figure 6C] FIG. 6 is a cross-sectional view of the VIC-VIC in FIG. 5 . [Figure 6D] FIG. 6 is a cross-sectional view of the VID-VID in FIG. 5 . [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII of FIG. 6A. [Figure 8A] FIG. 2 is a plan view showing a waveform of an opening in a shoulder sipe according to an embodiment of the present invention; [Figure 8B] FIG. 4 is a plan view showing a schematic bottom of a wave-shaped shape in a shoulder sipe of an embodiment. [Figure 9A] FIG. 4 is a plan view showing a schematic diagram of a wave-shaped opening in a central sipe of the embodiment. [Figure 9B] FIG. 4 is a plan view showing a schematic bottom of a wave-shaped shape of a central sipe of the embodiment. [Figure 10A] FIG. 4 is a plan view showing a waveform of an opening in an intermediate sipe according to an embodiment of the present invention; [Figure 10B] FIG. 4 is a plan view showing a schematic bottom of a wave-shaped shape in an intermediate sipe according to an embodiment. [Figure 11] FIG. 2 is a plan view selectively showing a shoulder block, a center block, and an intermediate block according to an embodiment, illustrating an angle of an extension direction of a sipe of each block with respect to the tire equator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment will be described with reference to the drawings. Fig. 1 is a plan view of a tire 1, which is a pneumatic tire according to an embodiment, showing a partially developed outer peripheral surface. The tire 1 of the embodiment can be used as a tire for passenger cars, but can also be used as a tire for various vehicles such as light trucks, trucks, and buses.

[0010] Fig. 1 shows a tire axial direction X and a tire circumferential direction C. In the tire 1 of the embodiment, the rotation direction when the vehicle mounted thereon moves forward is determined to be one side of the tire circumferential direction, and the direction C1 shown in Fig. 1 is that rotation direction. Note that in the following description, the front side refers to the right side of Fig. 1, which is the forward direction of the vehicle according to the tire rotation direction C1, and the rear side refers to the left side of Fig. 1, which is the backward direction of the vehicle according to a rotation direction C2 opposite to the tire rotation direction C1.

[0011] 1 shows a tread 10 of a tire 1 and shoulders 30 on both axial sides of the tread 10. The shoulders 30 are portions that transition from the tread 10 to sidewalls (not shown) on both axial sides of the tire, and correspond to the shoulders of the tire 1. The shoulders 30 include a first shoulder 31 on the upper side in FIG. 1 and a second shoulder 32 on the lower side in FIG. 2.

[0012] (Tread pattern) The tread 10 has a tread surface 20 that comes into contact with the road surface. A tread pattern 11 is formed on the tread surface 20. The main design of the tread pattern 11 is formed by a plurality of grooves 12 and a plurality of blocks 13 defined by the grooves 12. Fig. 1 shows a tire equator S1, which is an imaginary line that extends through the center of the tread surface 20 in the axial direction of the tire along the tire circumferential direction.

[0013] If the tire axial direction is the left-right direction, the tread pattern 11 is substantially symmetrical with respect to the tire equator S1, except for a slight positional shift in the tire circumferential direction. The tread surface 20 includes a first tread surface 21 on the first shoulder 31 side and a second tread surface 22 on the second shoulder 32 side, with the tire equator S1 as the boundary.

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

[0015] The inclined grooves 40 extend 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 multiple 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 formed mainly in the first tread surface 21, and the second inclined groove 42 is formed mainly in the second tread surface 22.

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

[0017] Since the tread pattern 11 is symmetrical, the first inclined grooves 41 and the second inclined grooves 42 have the same configuration, and the first communicating grooves 51 and the second communicating grooves 52 have the same configuration.

[0018] The first inclined groove 41 is a groove that extends forward from the first shoulder 31 toward the tire equator S1 while gradually curving so that the rear side is convex, and is generally inclined with respect to the tire circumferential direction. The second inclined groove 42 is a groove that extends forward from the second shoulder 32 toward the tire equator S1 while gradually curving so that the rear side is convex, and is generally inclined with respect to the tire circumferential direction. Here, in each of the inclined grooves 41, 42, the end on the shoulder 30 (first shoulder 31, 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 base end curved portion 43 extending from the base end to the vicinity of the center of the first tread surface 21 in the tire axial direction, and a tip end curved portion 44 curving from the end of the base end curved portion 43 on the tire equator S1 side toward the tire equator S1 to the tip end. The base end curved portion 43 is curved with a relatively small curvature and is slightly inclined forward. The tip end curved portion 44 is curved with the same curvature as the base end curved portion 43 and is inclined forward at a steeper angle than the base end curved portion 43.

[0020] The second inclined groove 42 has a similar configuration to the first inclined groove 41. That is, the second inclined groove 42 includes a base end side curved portion 43 extending from the base end to approximately passing the tire axial center of the second tread surface 22, and a tip end side curved portion 44 curving from the end of the base end side curved portion 43 on the tire equator S1 side toward the tire equator S1 to the tip.

[0021] The first inclined grooves 41 arranged in the tire circumferential direction are alternately different in length. The tip of the shorter first inclined groove 41 terminates in a manner to join the second inclined groove 42 immediately before the tire equator S1. The tip of the longer first inclined groove 41 passes the tire equator S1, then crosses the tip side curved portions 44 of the two second inclined grooves 42 adjacent in the tire circumferential direction, and then terminates.

[0022] The lengths of the second inclined grooves 42 also vary alternately in the tire circumferential direction, similar to the first inclined grooves 41. That is, the tips of the shorter second inclined grooves 42 terminate in a manner to join the first inclined grooves 41 immediately before the tire equator S1. The tips of the longer second inclined grooves 42 pass the tire equator S1, then cross the tip-side curved portions 44 of the two first inclined grooves 41 adjacent in the tire circumferential direction, and then terminate.

[0023] The first communicating groove 51 extends straight from the end of the tip-side curved portion 44 of the first inclined groove 41 closest to the base-side curved portion 43 to near the bend point where the first inclined groove 41 transitions from the base-side curved portion 43 to the tip-side curved portion 44 on the circumferential front side of the tire.

[0024] The second communicating groove 52 is similar to the first communicating groove 51 and extends straight from the end of the tip-side curved portion 44 of the second inclined groove 42 closest to the base-side curved portion 43 to near the bend point where the second inclined groove 42 transitions from the base-side curved portion 43 to the tip-side curved portion 44 on the circumferential front side of the tire.

[0025] The first communicating groove 51 and the second communicating groove 52 are both inclined with respect to the tire circumferential direction so as to extend from the rear side to the front side and toward the outside in the tire circumferential direction.

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

[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 defined in a substantially rectangular shape by a pair of circumferentially adjacent first inclined grooves 41 and a first communicating 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 multiple first shoulder blocks 61 are lined up in the circumferential direction of the tire with the base end side curved portion 43 of the first inclined groove 41 between them.

[0029] The second shoulder block 62 is defined in a substantially rectangular shape by a pair of second inclined grooves 42 adjacent in the tire circumferential direction and the second communicating 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 multiple second shoulder blocks 62 are lined up in the tire circumferential direction with the base end side curved portion 43 of the second inclined groove 42 between them.

[0030] The first shoulder block 61 and the second shoulder block 62, which are arranged in the circumferential direction of the tire on either side of the base end curved portion 43 of the inclined groove 40, may be arranged at equal intervals in the circumferential direction of the tire, or may be arranged at a variable pitch that is unequal intervals.

[0031] The central blocks 70 are arranged so as to straddle both the first tread surface 21 and the second tread surface 22. That is, the tire equator S1 passes through all of the central blocks 70. The multiple central blocks 70 include multiple first central blocks 71 that are mainly present on the first tread surface 21 side, and multiple second central blocks 72 that are mainly present on the second tread surface 22 side.

[0032] The proportion of the surface area of ​​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 defined in 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 and the tip side curved portion 44 of the second inclined groove 42 that is longer among the multiple second inclined grooves 42.

[0033] The proportion of the surface area of ​​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 defined 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 and the tip side curved portion 44 of the first inclined groove 41 that is longer among the multiple first inclined grooves 41.

[0034] The multiple first central blocks 71 and the multiple second central blocks 72 are arranged alternately in the tire circumferential direction.

[0035] The intermediate blocks 80 include 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 defined in a substantially rectangular shape by the tip side curved portions 44 of a pair of first inclined grooves 41 adjacent in the tire circumferential direction, the first communicating groove 51, and the tip side curved portion 44 of the longer second inclined groove 42. The multiple first intermediate blocks 81 are lined up in the tire circumferential direction with the tip side curved portions 44 of the first inclined grooves 41 in between.

[0037] The second intermediate block 82 is defined in a substantially rectangular shape by the tip side curved portions 44 of a pair of second inclined grooves 42 adjacent in the tire circumferential direction, the second communicating groove 52, and the tip side curved portion 44 of the longer second inclined groove 42. The multiple second intermediate blocks 82 are lined up in the tire circumferential direction with the tip side curved portions 44 of the second inclined grooves 42 in between.

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

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

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

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

[0042] In both the first tread surface 21 and the second tread surface 22, the intermediate blocks 80 in a row that does not have a central block 70 have a longer length in the extension direction along the inclined groove 40 than the intermediate blocks 80 in a row that has a central block 70. On the other hand, the shoulder blocks 60 and the central blocks 70 have the same length in the extension direction along the inclined groove 40.

[0043] (Block sipes) As shown in FIG. 1, each block 13 of the tread 10 has a plurality of sipes 14. The plurality of sipes 14 includes shoulder sipes 110 formed in each of the first shoulder block 61 and the second shoulder block 62 (hereinafter, sometimes collectively referred to as shoulder blocks 60), central sipes 120 formed in each of the first central block 71 and the second central block 72 (hereinafter, sometimes collectively referred to as central blocks 70), and intermediate sipes 130 formed in each of the first intermediate block 81 and the second intermediate block 82 (hereinafter, sometimes collectively referred to as intermediate blocks 80). Each sipe has a groove width smaller than the above-mentioned inclined groove 40 and the communication groove 50, and the groove width is 1 mm or less. The number of sipes 14 per block 13 is arbitrary, but for example, about two to five sipes 14 are arranged in one block 13.

[0044] The shoulder sipes 110, the central sipes 120 and the intermediate sipes 130 are all open on the surfaces of the blocks 60, 70 and 80, and have an overall wave-shaped shape when viewed from the tire surface. The depth direction of each of the sipes 110, 120 and 130 is generally aligned 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 extend generally straight. In each shoulder block 60, the plurality of shoulder sipes 110 are arranged parallel to each other at intervals. The plurality of shoulder sipes 110 extend generally parallel to the extension 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 end of the shoulder sipe 110 on the inner side in the tire axial direction (the tire equator S1 side) communicates with the first communicating groove 51 and the second communicating groove 52 (hereinafter, sometimes collectively referred to as the communicating groove 50). The end of the shoulder sipe 110 on the outer side in the tire axial direction (the shoulder 30 side) terminates without reaching the end of the shoulder block 60 on the outer side in the tire axial direction.

[0046] Fig. 2 is a perspective view showing one shoulder sipe 110. Fig. 3A is a view taken along the line IIIA-IIIA in Fig. 2. Fig. 3B is a cross-sectional view taken along the line IIIB-IIIB in Fig. 2. Fig. 3C is a cross-sectional view taken along the line IIIC-IIIC in Fig. 2. Fig. 3D is a cross-sectional view taken along the line IIID-IIID in Fig. 2. Fig. 4 is a cross-sectional view taken along the line 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 extension direction, and a sipe bridge 114 that extends straight from one end of the corrugated portion 113 to the communicating groove 50 and has a smaller depth than the corrugated portion 113. The shoulder sipe 110 also has an opening 113A on the surface of the shoulder block 60 and a bottom 113B. The corrugated portion 113 occupies a large portion, for example, 70% or more, of the extension direction length of the shoulder sipe 110. The depth of the corrugated portion 113 from the opening 113A to the bottom 113B 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 FIG. 2 and FIG. 3A to FIG. 3D, the corrugated portion 113 of the shoulder sipe 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 largest at the opening 113A and smallest at the bottom 113B. That is, the bottom 113B also has an amplitude, and the bottom 113B does not have a linear shape. The amplitudes of the openings 113A on the surface of the shoulder block 60 of the multiple shoulder sipes 110 are the same as each other. Furthermore, the amplitude of the shoulder sipe 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 sipe 110, has a substantially constant dimension from the opening 113A to the bottom 113B. 4, the shoulder sipe 110 is linear from the opening 113A to the bottom 113B in a cross-sectional view in a depth direction substantially perpendicular to the extension direction of the shoulder sipe 110. The width of the shoulder sipe 110 is preferably 0.5 mm or more and 1.5 mm or less.

[0049] 2 and 3B to 3D, the shoulder sipe 110 of the embodiment has a portion where the corrugated portion 113 is not continuous in the extending direction and is missing. This is one example of the shoulder sipe 110, and the shoulder sipe 110 is not limited to this, and may have a continuous corrugated shape.

[0050] As shown in FIG. 1, each central block 70 has a plurality of central sipes 120. The central sipes 120 extend generally straight. In each central block 70, the multiple central sipes 120 are arranged parallel to one another at intervals. The multiple central sipes 120 extend approximately parallel to the tire axial direction. In other words, the central sipes 120 extend in a direction intersecting the tire circumferential direction. Each of the two ends of the central sipes 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 sipe 120. Fig. 6A is a VIA-VIA arrow view of Fig. 5. Fig. 6B is a VIB-VIB cross-sectional view of Fig. 5. Fig. 6C is a VIC-VIC cross-sectional view of Fig. 5. Fig. 6D is a VID-VID cross-sectional view of Fig. 5. Fig. 7 is a VII-VII cross-sectional view of Fig. 6A.

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

[0053] As shown in FIG. 5 and FIG. 6A to FIG. 6D, the wavy portion 123 of the central sipe 120 is formed in a wavy shape having a constant period from the opening 123A to the bottom 123B. The amplitude of the wavy portion 123 is largest at the opening 123A and smallest at the bottom 123B. That is, the bottom 123B also has an amplitude, and the bottom 123B does not have a linear shape. The amplitudes of the openings 123A on the surface of the central block 70 of the multiple central sipes 120 are the same as each other. Furthermore, the amplitude of the central sipe 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 sipe 120, has a substantially constant dimension from the opening 123A to the bottom 123B. 7, the central sipe 120 is linear from the opening 123A to the bottom 123B in a depth direction cross section substantially perpendicular to the extension direction of the central sipe 120. The width of the central sipe 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. The intermediate sipes 130 extend generally straight. In each intermediate block 80, the plurality of intermediate sipes 130 are arranged parallel to one another at intervals. Each of the plurality of intermediate sipes 130 is inclined with respect to the tire circumferential direction so as to extend from the rear side to the front side toward the tire circumferential outer side. In other words, the intermediate sipes 130 extend in a direction intersecting with the tire circumferential direction. Each of both ends of the intermediate sipes 130 communicates with either the inclined groove 40 or the communicating groove 50.

[0055] The intermediate sipe 130 has a similar configuration to the above-mentioned central sipe 120. That is, although not shown, the intermediate sipe 130 has portions similar to the corrugated portion 123, the first sipe bridge 121, and the second sipe bridge 122 in the central sipe 120. The period of the corrugated portion of the intermediate sipe 130 is constant, and the amplitude is largest at the opening on the surface of the central block 70 and smallest at the bottom. The amplitudes of the openings on the surface of the intermediate block 80 of the multiple intermediate sipes 130 are the same as each other. The width of the intermediate sipe 130 is approximately constant from the opening to the bottom. As a result, in a cross-sectional view in the depth direction approximately perpendicular to the extension direction of the intermediate sipe 130, the intermediate sipe 130 is linear from the opening to the bottom. The width of the intermediate sipe 130 is preferably 0.5 mm or more and 1.5 mm or less.

[0056] FIG. 8A is a plan view showing a waveform of the opening 113A in the shoulder sipe 110, and shows the amplitude ShA of the opening 113A. FIG. 8B is a plan view showing a waveform of the bottom 113B in the shoulder sipe 110, and shows the amplitude ShB of the bottom 113B. FIG. 9A is a plan view showing a waveform of the opening 123A in the central sipe 120, and shows the amplitude CeA of the opening 123A. FIG. 9B is a plan view showing a waveform of the bottom 123B in the central sipe 120, and shows the amplitude CeB of the bottom 123B. FIG. 10A is a plan view showing a waveform of the opening 133A in the intermediate sipe 130, and shows the amplitude MeA of the opening 133A. FIG. 10B is a plan view that shows a schematic view of the bottom 133B of the wave shape of the intermediate sipe 130, and shows the amplitude MeB of the bottom 133B.

[0057] In the embodiment, the amplitudes ShA, CeA, and MeA are not the same, and the amplitude ShA of the shoulder sipe 110 is the smallest, and the amplitude CeA of the central sipe 120 and the amplitude MeA of the intermediate sipe 130 are the same, or the amplitude CeA of the central sipe 120 is larger than the amplitude MeA of the intermediate sipe 130. That is, it is specified that "CeA ≧ MeA > ShA".

[0058] With the condition "CeA≧MeA>ShA", it is preferable that each of these amplitudes CeA, MeA, and ShA is 0.5 mm or more and 1.5 mm or less.

[0059] Moreover, it is preferable that the amplitude ShB of the bottom 113B of the shoulder sipe 110, the amplitude CeB of the bottom 123B of the central sipe 120, and the amplitude MeB of the bottom 133B of the intermediate sipe 130 are each 0.1 mm or more and 0.6 mm or less.

[0060] In addition, when the amplitude of the openings 113A, 123A, 133A of each sipe 110, 120, 130 is A, and the amplitude of the bottoms 113B, 123B, 133B of each sipe 110, 120, 130 is B, the ratio A / B of the amplitude A to the amplitude B of each sipe is preferably 4.0 or more and 7.0 or less. That is, each of ShA / ShB in the shoulder sipe 110, CeA / CeB in the central sipe 120, and MeA / MeB in the intermediate sipe 130 is preferably 4.0 or more and 7.0 or less.

[0061] 11 is a plan view showing an excerpt of a block row 13A including a first shoulder block 61, a first central block 71, and a first intermediate block 81 extending along the first inclined groove 41 on the first tread surface 21. In FIG. 11, the angle of the extension direction of each sipe with respect to the tire equator S1 along the tire circumferential direction is shown as Shθ for the angle of the extension direction of the shoulder sipe 110, Ceθ for the angle of the extension direction of the central sipe 120, and Meθ for the angle of the extension direction of the intermediate sipe 130. All of these angles are angles that intersect with the tire equator S1 in the range of 0° to 90°. In the embodiment, these angles are specified as "Ceθ>Shθ>Meθ".

[0062] The angle Ceθ of the central sipe 120 is, for example, 90°, the angle Shθ of the shoulder sipe 110 is, for example, 75°, and the angle Meθ of the intermediate sipe 130 is, for example, 53°, but are not limited to these as long as they satisfy the above specified ranges.

[0063] In each block, the sipes extend substantially parallel to each other. Therefore, each of the sipes in the same block extends at the same angle with respect to the tire equator S1. That is, the angles Shθ of the shoulder sipes 110 in the same shoulder block 60 are the same. The angles Ceθ of the central sipes 120 in the same central block 70 are the same. The angles Meθ of the intermediate sipes 130 in the same intermediate block 80 are the same.

[0064] Although not shown, the extending directions of the sipes of the second shoulder blocks 62, the second center blocks 72 and the second intermediate blocks 82 on the second tread surface 22 side are also regulated by angles similar to those described above.

[0065] The tire 1 of the above embodiment provides the following advantages.

[0066] (1) A tire 1 according to the embodiment includes a tread 10, and the tread 10 includes a block 13 having a sipe 14 extending in a direction intersecting with the tire circumferential direction. The sipe 14 has a wave-shaped amplitude in the extension direction of the sipe 14 from the opening to the bottom on the surface of the block 13, and the amplitude is largest at the opening and smallest at the bottom. The amplitude decreases at a constant rate from the opening to the bottom, so that the sipe 14 is linear from the opening to the bottom in a cross-sectional view in the depth direction substantially perpendicular to the extension direction of the sipe 14. The openings of the sipes referred to here are the openings 113A of the shoulder sipes 110, the openings 123A of the central sipes 120, and the openings 133A of the intermediate sipes 130. The bottoms of the sipes referred to here are the bottoms 113B of the shoulder sipes 110, the bottoms 123B of the central sipes 120, and the bottoms 133B of the intermediate sipes 130.

[0067] The bottom of each sipe 14 in the embodiment does not have a straight line shape along the extension direction of the sipe 14, but has an amplitude. When stress is applied to the block 13 of the tread surface 20 during braking or starting of the vehicle, both sides of the sipe 14 of the block 13 tend to collapse depending on the direction of the stress. At this time, when the bottom of the sipe 14 is straight line shaped, the wave-shaped shape has a higher resistance to the stress. Therefore, the block 13 is less likely to be distorted, and the reduction in the ground contact area of ​​the surface of the block 13 is suppressed. This improves the ground contact. In addition, since the distortion of the block 13 is suppressed, the defect of block chipping, in which part or the entire block 13 is peeled off, is suppressed, and the durability of the tire 1 is improved.

[0068] In the embodiment, the amplitude of each sipe 14 decreases at a constant rate from the opening to the bottom on the surface of each block 13, so that each sipe 14 is linear from the opening to the bottom in a cross-sectional view in the depth direction substantially perpendicular to the extension direction of each sipe 14. As a result, the starting point of the collapse of the block 13 described above becomes the bottom of the sipe 14. In addition, both side portions of the sipe 14 in the block 13 are easily interlocked with each other, improving ground contact. Improved ground contact leads to improved cornering characteristics and driving stability.

[0069] (2) In the tire 1 according to the embodiment (1) above, the amplitude of the opening of the sipe 14 on the surface of the block 13 is preferably 0.5 mm or more and 1.5 mm or less.

[0070] This makes it easier to obtain the above-mentioned effects.

[0071] (3) In the tire 1 according to the above embodiment (1) and (2), the amplitude of the bottom of the sipe 14 is preferably 0.1 mm or more and 0.6 mm or less.

[0072] This makes it easier to obtain the above-mentioned effects.

[0073] (4) In the tire 1 according to the above embodiments (1) to (3), the width of the sipes 14 is preferably 0.5 mm or more and 1.5 mm or less.

[0074] This makes it easier to obtain the above-mentioned effects.

[0075] (5) In the tire 1 according to the above embodiments (1) to (4), 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 greater and 7.0 or less.

[0076] This makes it easier to obtain the above-mentioned effects.

[0077] (6) A tire 1 according to an embodiment has a tread 10. The tread 10 includes a plurality of blocks 13 arranged in a tire circumferential direction. The plurality of blocks 13 includes a plurality of shoulder blocks 60 arranged on the outermost sides in the tire axial direction, a plurality of central 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 central blocks 70 in the tire axial direction. The shoulder blocks 60 have a wave-shaped shape when viewed from the tire surface and at least one extending in a direction intersecting the tire circumferential direction. The tire has shoulder sipes 110, the central block 70 has at least one central sipe 120 which has a wavy shape when viewed on the tire surface and extends in a direction intersecting the tire circumferential direction, and the intermediate block 80 has at least one intermediate sipe 130 which has a wavy shape when viewed on the tire surface and extends in a direction intersecting the tire circumferential direction, and where the amplitude of the shoulder sipe 110 on the tire surface is ShA, the amplitude of the central sipe 120 on the tire surface is CeA, and the amplitude of the intermediate sipe 130 on the tire surface is MeA, CeA≧MeA>ShA.

[0078] In general, in pneumatic tires, the ground pressure on blocks arranged in the shoulder region tends to be large, and in particular, the periphery of sipes with a wave-shaped shape with a large amplitude is likely to receive large pressure. Here, in the tire 1 of the embodiment, the amplitude of the shoulder sipe 110 of the shoulder block 60 on the tire surface is made smaller than that of the central sipe 120 of the central block 70 and the intermediate sipe 130 of the intermediate block 80. This also distributes the ground pressure applied to the shoulder block 60, making it difficult for distortion to occur on both sides of the shoulder sipe 110. Therefore, problems such as local wear and block chipping in the shoulder block 60 are unlikely to occur. The shoulder block 60 contributes to driving stability, especially on snow-covered road surfaces, so that local wear and block chipping are suppressed, thereby ensuring driving stability on snow-covered road surfaces.

[0079] The intermediate block 80 has a large effect on driving stability on dry roads and also on snowy roads. The amplitude of the intermediate sipes 130 of the intermediate block 80 is larger than that of the shoulder sipes 110 and is equal to or smaller than that of the central sipes 120, thereby ensuring driving stability on both dry and snowy roads.

[0080] (7) In the tire 1 of the above embodiment (1), if the angle of the extension direction of the shoulder sipes 110 with respect to the tire circumferential direction in the range of 0° or more and 90° or less is Shθ, the angle of the extension direction of the central sipes 120 with respect to the tire circumferential direction in the range of 0° or more and 90° or less is Ceθ, and the angle of the extension direction of the intermediate sipes 130 with respect to the tire circumferential direction in the range of 0° or more and 90° or less is Meθ, it is preferable that Ceθ>Shθ>Meθ.

[0081] This provides a good balance between road contact during acceleration / braking on dry roads and grip performance due to the edge effect on snowy roads.

[0082] (8) In the tire 1 according to the above embodiments (6) and (7), the shoulder block 60 has a plurality of shoulder sipes 110, the central block 70 has a plurality of central sipes 120, and the intermediate block 80 has a plurality of intermediate sipes 130, and the amplitudes of the multiple shoulder sipes 110 on the tire surface are the same as each other, the amplitudes of the multiple central sipes 120 on the tire surface are the same as each other, and the amplitudes of the multiple intermediate sipes 130 on the tire surface are the same as each other.

[0083] This makes the amount of collapse of the blocks uniform, thereby suppressing block chipping.

[0084] (9) In the tire 1 according to the above embodiments (6) to (8), it is preferable that the shoulder block 60 has a plurality of shoulder sipes 110, the central block 70 has a plurality of central sipes 120, and the intermediate block 80 has a plurality of intermediate sipes 130, and that the Shθ of the multiple shoulder sipes 110 are the same as each other, the Ceθ of the multiple central sipes 120 are the same as each other, and the Meθ of the multiple intermediate sipes 130 are the same as each other.

[0085] This makes it possible to standardize the direction in which blocks collapse and the amount of collapse on each type of road surface, such as dry, wet, or snow-covered surfaces, thereby stabilizing ground contact and achieving a good balance between grip performance and the effect of suppressing block chipping.

[0086] (10) In the tire 1 according to the above embodiments (6) to (9), the tire rotation direction when mounted on a vehicle is preferably set to one side in the tire circumferential direction.

[0087] This makes it possible to standardize the direction in which blocks collapse and the amount of collapse on each type of road surface, such as dry, wet, or snow-covered surfaces, thereby stabilizing ground contact and achieving a good balance between grip performance and the effect of suppressing block chipping.

[0088] The present invention is not limited to the above-described embodiment, and even if modifications and improvements are made within the scope of the present invention, they will still be included in the scope of the present invention.

[0089] For example, the wave-shaped portion of each sipe may be a wave-shaped shape like a trigonometric function period, or may be a wave-shaped shape in which only the apex portion has a relatively large curvature R-shape and the portions between the apexes are straight lines. The R of the apex or the curvature radius of the R portion transitioning from the sipe bridge to the wave-shaped portion may be any value, but may be, for example, about 0.6 mm. [Explanation of symbols]

[0090] 1...Tire (pneumatic tire) 10…Tread 13…Block 60…Shoulder block 70…Central block 80…Middle block 110…Shoulder sipes 120…Central sipe 130...Middle sipe

Claims

1. A pneumatic tire having a tread, The tread includes a plurality of blocks arranged in a tire circumferential direction, The plurality of blocks include A plurality of shoulder blocks disposed outermost in an axial direction of the tire; A plurality of central blocks arranged at a center in an axial direction of the tire; a plurality of intermediate blocks disposed between the shoulder blocks and the center block in the tire axial direction, The shoulder block has at least one shoulder sipe that has a wave-shaped shape when seen from a surface of the tire and extends in a direction intersecting the tire circumferential direction, The central block has at least one central sipe that has a wave-shaped shape when seen from a surface of the tire and extends in a direction intersecting the tire circumferential direction, The intermediate block has at least one intermediate sipe that has a wave-shaped shape when seen from a tire surface view and extends in a direction intersecting the tire circumferential direction, The amplitude of the shoulder sipe on the tire surface is ShA, The amplitude of the central sipe on the tire surface is CeA, When the amplitude of the intermediate sipe on the tire surface is MeA, A pneumatic tire, wherein CeA≧MeA>ShA.

2. The angle of the extension direction of the shoulder sipe with respect to the tire circumferential direction in the range of 0° to 90° is Shθ, The angle of the extension direction of the central sipe with respect to the tire circumferential direction in the range of 0° to 90° is Ceθ, When the angle of the extension direction of the intermediate sipe with respect to the tire circumferential direction is Meθ in the range of 0° or more and 90° or less, The pneumatic tire according to claim 1 , wherein Ceθ>Shθ>Meθ.

3. The shoulder block has a plurality of the shoulder sipes, The central block has a plurality of the central sipes, The intermediate block has a plurality of the intermediate sipes, The amplitudes of the shoulder sipes on the tire surface are the same as each other, The amplitudes of the central sipes on the tire surface are the same as each other, The pneumatic tire according to claim 1 or 2, wherein the amplitudes of the intermediate sipes on the tire surface are the same as each other.

4. The shoulder block has a plurality of the shoulder sipes, The central block has a plurality of the central sipes, The intermediate block has a plurality of the intermediate sipes, The Shθ of the multiple shoulder sipes are the same as each other, The Ceθ of the multiple central sipes are the same as each other, The pneumatic tire according to claim 2 , wherein the Meθ of each of the intermediate sipes is the same as that of the other intermediate sipes.

5. 3. The pneumatic tire according to claim 1, wherein a rotation direction of the tire when mounted on a vehicle is set to one side in a tire circumferential direction.

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