tire

Abstract

To provide a tire that exhibits minimal deterioration in drainage and traction characteristics even as tire wear progresses. [Solution] The tire 1 has groove bottoms 511, 521 with a width of less than 4 mm, first wall surfaces 512, 522 extending radially outward from the groove bottoms 511, 521, and second wall surfaces 513, 523 extending radially outward from the groove bottoms 511, 521 opposite to the first wall surfaces 512, 522. When viewed from the radially outward side of the tire, the width of the second wall surfaces 513, 523 includes a portion that is wider than the width of the groove bottoms 511, 521, and the second wall surfaces 513, 523 are composed of inclined surfaces that are more inclined than the first wall surfaces 512, 522, and widening grooves (510, 520) that widen in the tire radially outward extend from the groove bottoms 511, 521 in a direction that intersects the tire circumferential direction.

Description

Technical Field

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[0001] The present disclosure relates to a tire.

Background Art

[0002] Conventionally, a tire having a groove in which an inclined surface is combined with a groove called a narrow groove width sipe is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a conventional tire having a groove in which an inclined surface is combined, when the tire wears, the inclined surface disappears, and particularly, the drainage characteristics and traction characteristics may deteriorate.

[0005] An object of the present disclosure is to provide a tire in which deterioration of drainage characteristics and traction characteristics is small even when tire wear progresses.

Means for Solving the Problems

[0006] The tire of the present disclosure has a groove bottom with a width of less than 4 mm, a first wall surface extending from the groove bottom to the outside in the tire radial direction, and a second wall surface extending from the opposite side of the first wall surface of the groove bottom to the outside in the tire radial direction. When viewed from the outside in the tire radial direction, the width of the second wall surface includes a portion wider than the width of the groove bottom, and the second wall surface is composed of an inclined surface inclined more than the first wall surface, and a width-expanding groove in which the groove width expands from the groove bottom toward the outside in the tire radial direction extends in a direction intersecting the tire circumferential direction.

[0007] Furthermore, the tire of this disclosure has a groove bottom with a width of less than 1.5 mm, a first wall surface extending radially from the groove bottom, and a second wall surface extending radially from the groove bottom on the opposite side of the first wall surface, wherein, when viewed from the outside in the radial direction of the tire, the width of the second wall surface includes a portion that is wider than the width of the groove bottom, and the second wall surface is composed of an inclined surface that is more inclined than the first wall surface, and a widening groove extends in a direction that intersects the circumferential direction of the tire, with the groove width widening toward the outside in the radial direction of the tire from the groove bottom. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a tire that exhibits minimal deterioration in drainage and traction characteristics even as tire wear progresses. [Brief explanation of the drawing]

[0009] [Figure 1] This is a partial perspective view of tire 1 as shown in this disclosure, viewed from the outside in the vehicle width direction. [Figure 2] This is a partial perspective view of tire 1 as shown in this disclosure, viewed from the inside in the vehicle width direction. [Figure 3] This is a partial unfolded view showing the tread surface of tire 1 according to the present disclosure in a planar manner. [Figure 4] This is a partially enlarged unfolded view of Figure 3, which is a further partial enlargement. [Figure 5] This is a cross-sectional view of the tire axial direction, obtained by cutting tire 1 at the position indicated by arrow AA in Figure 3. [Figure 6] This is a cross-sectional view of the center width expansion groove 510, taken at the position indicated by arrow DD in Figure 4, in a direction perpendicular to the extension direction of the center width expansion groove 510. [Figure 7] This is a cross-sectional view taken at the position of arrow EE in Figure 4, in a direction perpendicular to the extension direction of the outer width expansion groove 520. [Figure 8] This is a cross-sectional view showing a modified form of the center width widened groove 510B, in which the shape of the second wall surface 513 has been changed. [Figure 9] This is a cross-sectional view showing a modified form of the second wall surface 513, which is the center width enlarged groove 510C. [Modes for carrying out the invention]

[0010] The following describes one embodiment for implementing this disclosure with reference to drawings and other materials.

[0011] (Embodiment) Figure 1 is a partial perspective view of the tire 1 according to this disclosure, viewed from the outside in the vehicle width direction. Figure 2 is a partial perspective view of the tire 1 according to this disclosure, viewed from the inside in the vehicle width direction. Figure 3 is a partial unfolded view showing the tread surface of the tire 1 according to this disclosure unfolded in a planar manner. Figure 4 is a partially enlarged unfolded view of Figure 3. Figure 5 is a cross-sectional view in the tire axis direction, obtained by cutting the tire 1 at the position of arrow AA in Figure 3. The tire 1 according to this embodiment is, for example, a tire for a passenger car. The configuration of the tire 1 according to this embodiment can be used for various vehicles other than passenger cars, such as light trucks, trucks, and buses. Furthermore, although the following description uses a pneumatic tire as an example, a non-pneumatic tire may also be used.

[0012] The cross-sectional shapes shown in Figures 1, 2, and 5 are axial cross-sectional views (tire meridian cross-sections) of the tire in an unloaded state, mounted on a standard rim (not shown) and filled with the standard internal pressure. The standard rim is the rim specified for each tire in the standard system, including the standard on which the tire is based. For example, it is the standard rim for JATMA, and the "Measuring Rim" for TRA and ETRTO. The standard internal pressure is the air pressure specified for each tire in the standard system, including the standard on which the tire is based. For truck and bus tires and light truck tires, it is the maximum air pressure for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and the "INFLATION PRESSURE" for ETRTO. For passenger car tires, it is usually 180 kPa, but for tires marked "Extra Load" or "Reinforced," it is 220 kPa.

[0013] In Figure 5, the symbol S1 represents the tire equatorial plane. The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis and located at the center of the tire axial direction. The basic internal structure of tire 1 is symmetrical in the tire axial cross-section with respect to the tire equatorial plane S1. As will be described later, the tread pattern of tire 1 in this embodiment is asymmetrical in the tire axial direction, so the internal structure of tire 1 may also be asymmetrical.

[0014] Here, the tire axis direction is the direction parallel to the tire rotation axis, and in the cross-sectional view of Figure 5, it is the left-right direction on the paper. In Figures 1, 2, and 5, it is shown as the tire axis direction X. The inner direction in the tire axis direction is the direction approaching the tire equatorial plane S1, and in Figure 5, it is the center side of the paper. The outer direction in the tire axis direction is the direction away from the tire equatorial plane S1, and in Figure 5, it is the left and right sides of the paper. The tire radial direction is the direction perpendicular to the tire rotation axis, and in Figure 1, it is the up-down direction on the paper. In Figures 1, 2, and 5, it is shown as the tire radial direction Y. The outer direction in the tire radial direction is the direction away from the tire rotation axis, and in Figure 5, it is the top side of the paper. The inner direction in the tire radial direction is the direction approaching the tire rotation axis, and in Figure 5, it is the bottom side of the paper.

[0015] The tread pattern 38 provided on the tread surface 37 of the tire 1 in the embodiments shown in Figures 1 to 5 is asymmetrical in the tire axial direction, and the orientation in which the tire 1 is mounted on the vehicle is specified. That is, of the two sides in the tire axial direction when the tire 1 is mounted on the vehicle, the side that is positioned on the outside of the vehicle and the side that is positioned on the inside of the vehicle are specified. The orientation in which the tire is mounted on the vehicle is based on the tread pattern 38. In Figures 1 to 5, the side of the tire 1 that is positioned on the outside of the vehicle is shown as the outside in the vehicle width direction, and the side that is positioned on the inside of the vehicle is shown as the inside in the vehicle width direction.

[0016] The tire 1 of the embodiment includes a pair of beads (not shown) provided on both sides in the tire axial direction, a pair of sidewalls (not shown) extending radially outward in the tire diameter direction from each of the pair of beads, a tread 30 disposed between the pair of sidewalls, a pair of shoulders 40 which are portions transitioning from each of the pair of sidewalls to the tread 30, a carcass ply (not shown) spanned and disposed between the pair of beads, and an inner liner (not shown) disposed on the tire inner cavity side of the carcass ply. Note that specific forms inside the tire such as beads, sidewalls, carcass plies, inner liners, etc. can appropriately use conventionally known configurations, so detailed descriptions thereof are omitted. Also, in addition to beads, sidewalls, carcass plies, inner liners, etc., it may have additional configurations, or some of these may be omitted.

[0017] The tread 30 has a tread rubber 36. The tread rubber 36 is disposed radially outside the tire diameter of the cap ply (not shown). The tread rubber 36 constitutes a tread surface 37 which is the outer surface of the tread 30.

[0018] The shoulder 40 includes an inner shoulder 40A disposed on the inner side in the vehicle width direction and an outer shoulder 40B disposed on the outer side in the vehicle width direction when the tire 1 is mounted on a vehicle.

[0019] Next, the tread pattern 38 will be described. FIGS. 3 and 4 show, in addition to the tire axial direction X, the outer side in the vehicle width direction, and the inner side in the vehicle width direction, the tire circumferential direction C and the tire equator S2. The tire equator S2 is a virtual line extending along the tire circumferential direction at the center in the tire axial direction.

[0020] As shown in Figures 1 to 5, the tread pattern 38 of the embodiment includes a plurality of main grooves 100 (110, 120, 130) and a plurality of planes 200 (210, 220, 240) that open into the tread surface 37. The planes 200 are partitioned in the direction of the tire axis, and each of the main grooves 100 is positioned between the planes 200. Both the plurality of main grooves 100 and the plurality of planes 200 extend in an annular shape along the circumferential direction of the tire. In the following description, the width direction in the main grooves 100 and planes 200 is the same direction as the direction of the tire axis, and the width in the main grooves 100 and planes 200 refers to the dimension in the direction of the tire axis.

[0021] In this embodiment, the main grooves 100 extend along the tire circumferential direction C, in parallel to each other in the order of inner main groove 110, intermediate main groove 120, and outer main groove 130, from the inside in the vehicle width direction to the outside in the vehicle width direction, in the axial direction of the tire.

[0022] The inner main groove 110 is positioned inward in the vehicle width direction from the tire equator S2 and the intermediate main groove 120 when the tire 1 is mounted on the vehicle.

[0023] The intermediate main groove 120 is positioned slightly inward in the vehicle width direction from the tire equator S2 when the tire 1 is mounted on the vehicle. The intermediate main groove 120 may also be positioned in a position that overlaps with the tire equator S2, or it may be positioned slightly outward in the vehicle width direction from the tire equator S2.

[0024] The outer main groove 130 is positioned outside the vehicle width direction of the tire equator S2 and the intermediate main groove 120 when the tire 1 is mounted on the vehicle.

[0025] The inner main groove 110, the intermediate main groove 120, and the outer main groove 130 have roughly the same width, for example, 5 mm to 15 mm, and their depth is approximately 6 mm to 18 mm, but is not limited to these. The width and depth of each main groove 100 (110, 120, 130) may all be different, or some may be the same.

[0026] In this embodiment, the ground plane 200 extends along the tire circumferential direction C in parallel to the tire axial direction, from the inside in the vehicle width direction to the outside in the vehicle width direction, in the order of inner shoulder ground plane 210, center ground plane 220 (first ground plane 221 and second ground plane 222), and outer shoulder ground plane 240.

[0027] The inner shoulder ridge 210 is positioned between the inner main groove 110 and the inner shoulder 40A. When the tire 1 is mounted on the vehicle, the inner shoulder ridge 210 is positioned inward in the vehicle width direction. The inner end of the inner shoulder ridge 210 in the vehicle width direction smoothly continues to the inner shoulder 40A.

[0028] The center ramp 220 is provided further outward in the vehicle width direction than the inner main groove 110 and further inward in the vehicle width direction than the outer main groove 130, and in this embodiment, it has a first ramp 221 and a second ramp 222.

[0029] The first rib 221 is positioned between the intermediate main groove 120 and the inner main groove 110. The second rib 222 is positioned between the intermediate main groove 120 and the outer main groove 130. Both the first rib 221 and the second rib 222 are rib-shaped portions that extend around the entire circumference of the tire. When the tire 1 is mounted on the vehicle, the first rib 221 is positioned further inward in the vehicle width direction than the second rib 222. The widths of the first rib 221 and the second rib 222 are approximately the same, for example, about 15 mm to 30 mm, but not limited to this. However, the widths of the first rib 221 and the second rib 222 may be different.

[0030] The outer shoulder ridge 240 is positioned between the outer main groove 130 and the outer shoulder 40B. When the tire 1 is mounted on the vehicle, the outer shoulder ridge 240 is positioned on the outside in the vehicle width direction. The outer end of the outer shoulder ridge 240 in the vehicle width direction smoothly continues to the outer shoulder 40B.

[0031] In this embodiment, the widths of the inner shoulder ridge 210 and the outer shoulder ridge 240 (the distance from the edge of the design of each ridge shape to the edge of the main groove) are greater than those of the first ridge 221 and the second ridge 222, and the width of the inner shoulder ridge 210 is slightly smaller than the width of the outer shoulder ridge 240. The width of the inner shoulder ridge 210 is, for example, about 30 mm to 60 mm, and the width of the outer shoulder ridge 240 is, for example, about 40 mm to 70 mm, but is not limited to these values. The width of the inner shoulder ridge 210 may be greater than the width of the outer shoulder ridge 240, or their widths may be the same.

[0032] Furthermore, the tread pattern 38 of the tire 1 in this embodiment is provided with multiple grooves, inclined surfaces, etc., in addition to the main grooves described above. These will be described below. First, the inclined surfaces that extend along the circumferential direction of the tire will be described.

[0033] An inner circumferential sloped portion 111 is provided on the edge of the inner main groove 110. The inner circumferential sloped portion 111 is provided in a chamfered manner on the edge of the groove wall on the inner side in the vehicle width direction of the inner main groove 110, that is, on the edge of the connection portion between the inner main groove 110 and the inner shoulder base 210. The inner circumferential sloped portion 111 is a slope inclined with respect to the tire radial direction, where the groove width widens toward the outer side in the tire radial direction, and extends in the tire circumferential direction C. The depth of the inner circumferential sloped portion 111 in the tire radial direction (depth from the surface of the inner shoulder base 210) can be, for example, 0.5 mm or more and 2.0 mm or less. The width of the inner circumferential sloped portion 111 in the tire axial direction can be 0.5 mm or more and 2.0 mm or less. The depth of the inner circumferential sloped portion 111 in the tire radial direction and the width in the tire axial direction are constant regardless of location. Note that "constant" does not mean strictly identical values; dimensional variations due to manufacturing tolerances, etc., are acceptable.

[0034] An intermediate circumferential sloped portion 121 is provided on the edge of the intermediate main groove 120. The intermediate circumferential sloped portion 121 is provided in a chamfered manner on the edge of the groove wall on the inner side in the vehicle width direction of the intermediate main groove 120, that is, on the edge of the connection portion between the intermediate main groove 120 and the first base 221. The intermediate circumferential sloped portion 121 is a slope inclined with respect to the tire radial direction, where the groove width widens toward the outer side in the tire radial direction, and extends in the tire circumferential direction C. The depth of the intermediate circumferential sloped portion 121 in the tire radial direction (depth from the surface of the first base 221) can be, for example, 0.5 mm or more and 2.0 mm or less. The width of the intermediate circumferential sloped portion 121 in the tire axial direction can be 0.5 mm or more and 2.0 mm or less. The depth of the intermediate circumferential sloped portion 121 in the tire radial direction and the width in the tire axial direction are constant regardless of location. Note that "constant" does not mean strictly identical values; dimensional variations due to manufacturing tolerances, etc., are acceptable.

[0035] An outer width-decreasing circumferential slope portion 450 is provided on the edge of the outer main groove 130. The outer width-decreasing circumferential slope portion 450 is provided in a chamfered manner on the edge of the groove wall on the outer side in the vehicle width direction of the outer main groove 130, that is, on the edge of the connection portion between the outer main groove 130 and the outer shoulder land 240. The outer width-decreasing circumferential slope portion 450 is a slope inclined with respect to the tire radial direction, where the groove width widens toward the outer side in the tire radial direction, and extends in the tire circumferential direction C. The width in the tire axial direction and the depth in the tire radial direction of the outer width-decreasing circumferential slope portion 450 change depending on the position in the tire circumferential direction C.

[0036] By providing slopes on the edges of each of the main grooves, drainage is improved, and uneven wear of the corresponding areas of the ramps (inner shoulder ramp 210, first ramp 221, outer shoulder ramp 240) can be suppressed. Furthermore, for the outer width-variable circumferential slope section 450, by providing sections with relatively large width and depth, the aesthetic appearance and drainage are improved, and by gradually decreasing the width and depth (hereinafter also referred to as "gradual change"), the effect of suppressing uneven wear is maintained, and the contact area is prevented from decreasing. Thus, it is possible to achieve both handling stability on dry road surfaces and handling stability on wet road surfaces.

[0037] Furthermore, it is desirable that the ratio of the depth of the inner circumferential slope portion 111 to the maximum depth of the outer width-decreasing circumferential slope portion 450 be between 5% and 40%. By setting the ratio of the depth of the inner circumferential slope portion 111 to the maximum depth of the outer width-decreasing circumferential slope portion 450 within the above range, drainage on the outer side in the vehicle width direction can be improved.

[0038] Furthermore, a center width variable circumferential slope portion 430 is provided approximately in the center of the tire axial direction of the second land section 222. The center width variable circumferential slope portion 430 is a slope inclined with respect to the tire radial direction, where the groove width widens toward the outer side in the tire radial direction, and extends in the tire circumferential direction C. The width in the tire axial direction and the depth in the tire radial direction of the center width variable circumferential slope portion 430 change depending on the position in the tire circumferential direction C.

[0039] The center width variable circumferential slope portion 430 has a shape obtained by rotating the outer width variable circumferential slope portion 450 by 180 degrees when viewed from the normal direction of the tread surface 37 in the tire deployed state. That is, the direction in which the width and depth are wider from the wider side to the narrower side is reversed between the center width variable circumferential slope portion 430 and the outer width variable circumferential slope portion 450. In the state shown in Figure 3, the side with the wider width and depth is the lower side of the paper for the center width variable circumferential slope portion 430, but the upper side of the paper for the outer width variable circumferential slope portion 450. As described above, the tread pattern 38 of the tire 1 of this embodiment is asymmetrical, and the direction of rotation during driving differs depending on the mounting position on the vehicle. However, since the width and depth of the center width-decreasing circumferential slope section 430 and the outer width-decreasing circumferential slope section 450 are in opposite directions from the wider side to the narrower side, the drainage characteristics do not change significantly regardless of the direction in which the tire 1 rotates, and stable drainage performance can be obtained.

[0040] The tire radial depth (depth from the surface of the outer shoulder land 240) of the outer width circumferential slope portion 450 and the center width circumferential slope portion 430 can be, for example, 0.3 mm to 1.0 mm at the point of minimum depth, and 3.5 mm to 6.0 mm at the point of maximum depth. However, it is desirable that the maximum tire radial depth of the outer width circumferential slope portion 450 and the center width circumferential slope portion 430 be shallower than the tire radial depth of the outer width expanding groove 520 and the tire radial depth of the center width expanding groove 510, which will be described later. This is because if the outer width circumferential slope portion 450 and the center width circumferential slope portion 430 are shallower than the center width expanding groove 510 and the outer width expanding groove 520, the rigidity of the second land 222 and the outer shoulder land 240 can be increased, enabling uniform contact and contributing to the suppression of uneven wear. Furthermore, the width of the outer width-decreasing circumferential slope portion 450 and the center width-decreasing circumferential slope portion 430 in the direction perpendicular to the direction of extension can be, for example, 0.5 mm or more and 1.5 mm or less at the part with the smallest width, and 2.5 mm or more and 7.0 mm or less at the part with the largest width.

[0041] Furthermore, the ground plane 200, namely the inner shoulder ground plane 210, the center ground plane 220 (first ground plane 221 and second ground plane 222), and the outer shoulder ground plane 240, are provided with multiple grooves having a component that extends in the axial direction of the tire (hereinafter also referred to as axial grooves). Conventionally, sipes, lug grooves, shelf sections, and narrow grooves have been used as axial grooves. Here, a sipe is defined as a groove whose width is preferably 2.0 mm or less, more preferably less than 1.5 mm, and whose groove depth (depth from the contact surface (tread surface 37)) is 4.5 mm or more and shallower than the groove depth of each main groove. A shelf section is defined as a groove that has the same groove width as a sipe but includes a portion that is shallower than a sipe. A lug groove is defined as a groove with a groove width of 4.0 mm or more. Narrow grooves with a groove width exceeding 2.0 mm and less than 4.0 mm are also sometimes used. The tread pattern 38 of the tire 1 in this embodiment does not have lug grooves as defined above as axial grooves. Rather, the tread pattern 38 is constructed by combining sipes, which are lateral grooves with a groove width of less than 4.0 mm, with slopes, narrow grooves, shelf sections, etc. By not providing lug grooves, pattern noise can be significantly reduced. Furthermore, by appropriately configuring each groove and slope, excellent effects such as noise reduction, improved drainage, and improved handling stability are achieved. The configuration of each of these grooves will be described below.

[0042] The inner shoulder ridge 210 is provided with a first sipe 310 and a second sipe 320.

[0043] In the unfolded view shown in Figure 3, the first sipe 310 extends approximately in the direction of the tire axis, but is slightly inclined relative to the tire axis. Furthermore, the first sipe 310 is formed in a slightly curved arc shape. The inner end of the first sipe 310 in the vehicle width direction is near the inner shoulder 40A, and the outer end in the vehicle width direction communicates with the inner main groove 110. The groove width of the first sipe 310 may be less than 1.5 mm, but for manufacturing reasons, it is desirable to have a groove width of 1.0 mm or more. The groove depth of the first sipe 310 can be, for example, 4.5 mm to 7.0 mm.

[0044] In the unfolded view shown in Figure 3, the second sipe 320 appears to have a shape similar to the first sipe 310. That is, in the unfolded view shown in Figure 3, the second sipe 320 extends roughly in the direction of the tire axis, but it extends with a slight inclination relative to the tire axis. Furthermore, the second sipe 320 is formed in a slightly curved arc shape.

[0045] The second sipe 320 has its inner end in the vehicle width direction near the inner shoulder 40A and communicates with the outer end in the tire axial direction via the end groove 321. The end groove 321 communicates with the second sipe 320 and the outer end in the tire axial direction, has a depth of 1 mm or less, and is wider toward the outer side in the tire axial direction.

[0046] Furthermore, although the outer end of the second sipe 320 in the vehicle width direction does not reach the inner main groove 110, it communicates with the inner main groove 110 via the end groove 322. The end groove 322 communicates with the second sipe 320 and the inner main groove 110, has a depth of 1.8 mm to 3.0 mm, and is wider toward the inner side in the tire axial direction.

[0047] The groove width of the second sipe 320 may be less than 1.5 mm, but it is preferable that it be 0.8 mm or more. The groove depth of the second sipe 320 can be, for example, 4.0 mm to 7.0 mm.

[0048] As described above, the inner side of the second sipe 320 in the vehicle width direction does not directly communicate with the outside, nor does the outer side of the second sipe 320 in the vehicle width direction directly communicate with the inner main groove 110. This prevents the inner shoulder ridge 210 from becoming excessively rigid. On the other hand, the inner side of the second sipe 320 in the vehicle width direction communicates with the outside via the end groove 321, and also communicates with the inner main groove 110 via the end groove 322. This ensures sufficient drainage and suppresses air pumping noise by ensuring an air passage.

[0049] Furthermore, as shown in Figure 3, the first sipe 310 and the second sipe 320 are arranged alternately in the tire circumferential direction C. This allows for uniform rigidity.

[0050] The first land area 221 is provided with a third sipe 330 and third sipe slopes 410 and 420.

[0051] In the unfolded view shown in Figure 3, the third sipe 330 extends diagonally at an angle to the inner main groove 110 and the intermediate main groove 120. Furthermore, the third sipe 330 is formed in a slightly curved arc shape.

[0052] The groove width of the third sipe 330 may be less than 1.5 mm, but it is preferable that it be 0.8 mm or more. The groove depth of the third sipe 330 can be, for example, between 4.0 mm and 7.0 mm.

[0053] The inner end of the third sipe 330 in the vehicle width direction is in communication with the inner main groove 110. On the other hand, the outer end of the third sipe 330 in the vehicle width direction is not in communication with the intermediate main groove 120. Therefore, the first rib 221 has a structure that is continuously connected around the entire circumference in the tire circumferential direction C. As a result, the intermediate main groove 120 is not in communication with it, which suppresses block deformation due to wiping and ensures rigidity as a circumferential rib. Wiping refers to the deformation of the tread rubber along the tire width direction due to the in-plane contraction force generated toward the center in the tire width direction as the tire makes contact with the road surface.

[0054] The third sipe slopes 410 and 420 are formed in a substantially chamfered manner on one edge of the third sipe 330, that is, on the edge of the connection portion between the third sipe 330 and the first land 221. The third sipe slopes 410 and 420 are slopes inclined with respect to the tire radial direction, with the groove width widening toward the radially outward direction of the tire, and extend along the third sipe 330.

[0055] The inner ends of the third sipe slopes 410 and 420 in the vehicle width direction are in communication with the inner main groove 110. On the other hand, the outer ends of the third sipe slopes 410 and 420 in the vehicle width direction do not reach the intermediate main groove 120 and are not in communication with it.

[0056] The third sipe slope 410 and the third sipe slope 420 have different lengths. The outer end of the third sipe slope 410 in the vehicle width direction is located near the center of the first land 221 in the tire axial direction. On the other hand, the outer end of the third sipe slope 420 in the vehicle width direction is located further outward in the vehicle width direction than near the center of the first land 221 in the tire axial direction, that is, further outward in the vehicle width direction than the outer end of the third sipe slope 410 in the vehicle width direction. In addition, the third sipe slope 410 and the third sipe slope 420 are arranged alternately in the tire circumferential direction C.

[0057] The depth of the third sipe slopes 410 and 420 in the tire radial direction (depth from the surface of the first land 221) can be, for example, 2.0 mm or more and 3.5 mm or less. The width of the third sipe slopes 410 and 420 in the direction perpendicular to the extension direction can be 1.5 mm or more and 3.5 mm or less. The depth of the third sipe slopes 410 and 420 in the tire radial direction and the width perpendicular to the extension direction are constant regardless of location. However, "constant" does not mean strictly identical values; dimensional variations due to manufacturing tolerances, etc., are permitted.

[0058] In addition to the center width variation circumferential slope section 430 described earlier, the second land section 222 is provided with a center width expansion groove 510 and a fourth sipe 350.

[0059] Figure 6 is a cross-sectional view of the center width widening groove 510, cut at the position of arrow DD in Figure 4, in a direction perpendicular to the extension direction of the center width widening groove 510. The center width widening groove 510 has a groove bottom 511, a first wall surface 512, and a second wall surface 513, and extends in a direction intersecting the tire circumferential direction C. More specifically, in the unfolded views shown in Figures 3 and 4, the center width widening groove 510 extends diagonally and linearly at an angle to the intermediate main groove 120.

[0060] The groove bottom 511 is recessed inward in the tire radial direction from the second land 222, forming the bottom of the center width widening groove 510, and has a shape that offsets the second land 222. The groove bottom 511 may have a width B511 of 2.0 mm or less, more preferably less than 1.5 mm, but it is desirable that it be 0.8 mm or more. The depth of the groove bottom 511 is the same as the depth D510 of the center width widening groove 510, and this depth D510 can be exemplified as 4.5 mm to 7.0 mm, but is shallower than the groove depth of the main groove 100 (inner main groove 110, intermediate main groove 120, outer main groove 130).

[0061] The first wall surface 512 extends radially outward from the groove bottom 511. In a cross-section perpendicular to the extension direction of the center width widening groove 510 shown in Figure 6, in this embodiment, the first wall surface 512 is approximately perpendicular to the groove bottom 511.

[0062] The second wall surface 513 extends radially outward from the opposite side of the groove bottom 511 from the first wall surface 512. Furthermore, the second wall surface 513 is composed of a more inclined surface than the first wall surface 512. That is, with respect to the groove bottom 511, the angle between the groove bottom 511 and the first wall surface 512 is approximately 90 degrees, while the angle between the groove bottom 511 and the second wall surface 513 is greater than 90 degrees. As shown in Figure 6, the inclination angle θ510 of the second wall surface is defined in a cross-section obtained by cutting the center width widening groove 510 in a direction perpendicular to the extension direction of the center width widening groove 510. The second wall inclination angle θ510 is the angle between the line segment connecting the intersection of the second wall surface 513 with the groove bottom 511 to the end of the second wall surface 513 on the radially outer side of the tire, and the line segment connecting the intersection of the first wall surface 512 with the groove bottom 511 to the end of the first wall surface 512 on the radially outer side of the tire. It is desirable that this second wall inclination angle θ510 is between 10 degrees and 40 degrees. That is, it is desirable that the angle between the line segment connecting the intersection of the second wall surface 513 with the groove bottom 511 to the end of the second wall surface 513 on the radially outer side of the tire, and the groove bottom 511, be between 100 degrees and 130 degrees. Because the angle θ510 is a relatively small angle as described above, the center width widening groove 510 can effectively function as a groove. Therefore, it has a larger groove width than conventional sipes or grooves alone that do not have an inclined surface like the second wall surface 513, and it can secure a water flow path until the end of wear, improving drainage.

[0063] The width B513 of the second wall surface 513 can be, for example, 0.5 mm or more and 1.5 mm or less at the narrowest part, and 2.5 mm or more and 7.0 mm or less at the widest part.

[0064] The second wall surface 513 has a constant depth, and when viewed from the outside in the tire radial direction, its width B513 gradually changes along the direction in which the center width widening groove 510 extends. Specifically, when viewed from the inside in the vehicle width direction toward the outside in the vehicle width direction, the width of the second wall surface 513 gradually widens along the direction in which the center width widening groove 510 extends. Also, when viewed from the outside in the tire radial direction, the width B513 of the second wall surface 513 includes a portion that is wider than the width of the groove bottom 511. This is to make it easier to discharge water that has entered the center width widening groove 510 into the center width widening groove 510 by increasing the width on the side that connects to the center width changing circumferential slope section 430. In this way, the center width widening groove 510 is a width widening groove in which the groove width widens from the groove bottom 511 toward the outside in the tire radial direction. In addition, the orientation of the first wall surface 512 and the second wall surface 513 of the center width widening groove 510 is aligned in the tire circumferential direction.

[0065] The inner end of the center width-enlarged groove 510 in the vehicle width direction does not communicate with the intermediate main groove 120. Also, the outer end of the center width-enlarged groove 510 in the vehicle width direction does not communicate with the fourth sipe 350 or the outer main groove 130. Therefore, the second rib 222 has a structure that is continuously connected around the entire circumference in the tire circumferential direction C. As a result, the intermediate main groove 120 is not connected, which suppresses block collapse due to wiping and ensures rigidity as a circumferential rib.

[0066] The outer end of the center width widening groove 510 in the vehicle width direction is connected to the center width changing circumferential slope portion 430. As a result, the width of the center width changing circumferential slope portion 430 is continuous with the narrower side, which equalizes the ground pressure and suppresses block collapse.

[0067] As described above, by providing the center width widening groove 510 on the center plane 220, the straight-line response can be improved.

[0068] In the unfolded views shown in Figures 3 and 4, the fourth sipe 350 extends diagonally and linearly at an angle to the intermediate main groove 120. Furthermore, the fourth sipe 350 is positioned on the extension line of the outer end of the center width-enhancing groove 510 in the vehicle width direction. The groove width and groove depth of the fourth sipe 350 can be, for example, within the same range as that of the first sipe 310.

[0069] The inner end of the fourth sipe 350 in the vehicle width direction does not communicate with the center width widening groove 510. However, the outer end of the fourth sipe 350 in the vehicle width direction communicates with the outer main groove 130.

[0070] In addition to the outer width-decreasing circumferential slope section 450 described earlier, the outer shoulder land 240 is provided with an outer width-expanding groove 520, a secondary groove 150, a shelf section 370, a shelf slope section 470, a fifth sipe 380, and a sixth sipe 390.

[0071] Figure 7 is a cross-sectional view of the outer width widening groove 520, taken at the position of arrow EE in Figure 4, in a direction perpendicular to the extension direction of the outer width widening groove 520. The outer width widening groove 520 has a groove bottom 521, a first wall surface 522, and a second wall surface 523, and extends in a direction intersecting the tire circumferential direction C. More specifically, in the unfolded views shown in Figures 3 and 4, the outer width widening groove 520 extends diagonally and linearly at an angle to the outer main groove 130.

[0072] The groove bottom 521 is recessed inward in the tire radial direction from the outer shoulder plane 240, forming the bottom of the outer width-expanding groove 520, and has a shape that offsets the outer shoulder plane 240. The width B521 of the groove bottom 521 is greater than 2.0 mm and less than 4.0 mm. The depth of the groove bottom 521 is the same as the depth D520 of the outer width-expanding groove 520, and this depth D520 can be exemplified as being between 4.5 mm and 7.0 mm, but is shallower than the groove depth of the main groove 100 (inner main groove 110, intermediate main groove 120, outer main groove 130).

[0073] The first wall surface 522 extends radially outward from the groove bottom 521. In a cross-section perpendicular to the direction of extension of the outer width-enlarged groove 520 shown in Figure 7, in this embodiment, the first wall surface 522 is approximately perpendicular to the groove bottom 521.

[0074] The second wall surface 523 extends radially outward from the opposite side of the groove bottom 521 from the first wall surface 522. Furthermore, the second wall surface 523 is composed of a more inclined surface than the first wall surface 522. That is, with respect to the groove bottom 521, the angle between the groove bottom 521 and the first wall surface 522 is approximately 90 degrees, while the angle between the groove bottom 521 and the second wall surface 523 is greater than 90 degrees. As shown in Figure 7, the inclination angle θ520 of the second wall surface is defined in a cross-section obtained by cutting the outer width-expanding groove 520 in a direction perpendicular to the extension direction of the outer width-expanding groove 520. The second wall inclination angle θ520 is the angle between the line segment connecting the intersection of the second wall 523 with the groove bottom 521 to the end of the second wall 523 on the radially outer side of the tire, and the line segment connecting the intersection of the first wall 522 with the groove bottom 521 to the end of the first wall 522 on the radially outer side of the tire. This second wall inclination angle θ520 is preferably between 25 degrees and 60 degrees. That is, the angle between the line segment connecting the intersection of the second wall 523 with the groove bottom 521 to the end of the second wall 523 on the radially outer side of the tire, and the groove bottom 521, is preferably between 115 degrees and 150 degrees. Because the angle θ520 is a relatively small angle as described above, the outer width-enlarged groove 520 can effectively function as a groove. Therefore, it has a larger groove width than conventional sipes or grooves alone that do not have an inclined surface like the second wall 523, and it can secure a water flow path until the end of wear, improving drainage.

[0075] The width B523 of the second wall surface 523 can be, for example, 0.5 mm or more and 1.5 mm or less at the narrowest part, and 2.5 mm or more and 7.0 mm or less at the widest part.

[0076] The second wall surface 523 has a constant depth, and when viewed from the outside in the tire radial direction, its width B523 gradually changes along the direction in which the outer width-expanding groove 520 extends. Specifically, when viewed from the inside in the vehicle width direction toward the outside in the vehicle width direction, the width of the second wall surface 523 gradually narrows along the direction in which the outer width-expanding groove 520 extends. Also, when viewed from the outside in the tire radial direction, the width B523 of the second wall surface 523 includes a portion that is wider than the width of the groove bottom 521. This is to make it easier to discharge water that has entered the outer main groove 130 into the outer width-expanding groove 520 by increasing the width on the side connected to the outer main groove 130.

[0077] The inner end of the outer width-expanding groove 520 in the vehicle width direction is connected to the outer width-decreasing circumferential slope section 450. This ensures that the width of the outer width-decreasing circumferential slope section 450 is continuous with the narrower side, equalizing the ground pressure and suppressing block collapse.

[0078] As described above, by providing the outer width-enhancing groove 520 on the outer shoulder land 240, steering stability can be improved.

[0079] Furthermore, the orientation of the first wall surface 522 and the second wall surface 523 of the outer width-enlarged groove 520 is aligned in the circumferential direction of the tire. Moreover, the orientation of the first wall surface 522 and the second wall surface 523 of the outer width-enlarged groove 520 is opposite to the orientation of the first wall surface 512 and the second wall surface 513 of the center width-enlarged groove 510. This suppresses changes in drainage characteristics and traction characteristics depending on the direction of tire rotation.

[0080] Furthermore, when the center width-expanding groove 510 and the outer width-expanding groove 520 are considered together as a width-expanding groove, the multiple width-expanding grooves are arranged such that the direction in which the second wall surface (inclined surface) is positioned alternates in the circumferential direction of the tire. This arrangement also helps to suppress changes in drainage characteristics and traction characteristics depending on the direction of tire rotation.

[0081] The inner end of the outer width-enlarged groove 520 in the vehicle width direction is in communication with the outer main groove 130. The outer end of the outer width-enlarged groove 520 in the vehicle width direction is in communication with the secondary groove 150.

[0082] The secondary groove 150 extends along the circumferential direction of the tire. The depth of the secondary groove 150 can be, for example, shallower than the main groove. Also, the width of the secondary groove 150 in the axial direction of the tire can be, for example, between 0.5 mm and 3.0 mm.

[0083] In the unfolded views shown in Figures 3 and 4, the shelf section 370 extends diagonally in a straight line at an angle to the sub-groove 150. The shelf section 370 is positioned on the extension of the outer width-enhancing groove 520. Here, we will explain the classification of "shelf section" and "sipe". As explained earlier, a sipe is a groove whose width is preferably 2.0 mm or less, more preferably less than 1.5 mm, and whose groove depth is 4.5 mm or more and shallower than the groove depth of each main groove. In contrast, a shelf section, as described above, includes a portion with a groove depth shallower than that of a sipe.

[0084] The groove width of the shelf section 370 does not need to be more than 4.0 mm, but for manufacturing reasons, it is preferable that it be 0.8 mm or more. The groove depth of the shelf section 370 can be, for example, 0.3 mm to 1.0 mm.

[0085] The inner end of the shelf section 370 in the vehicle width direction is in communication with the sub-groove 150. The outer end of the shelf section 370 in the vehicle width direction is located midway along the outer shoulder 240 and is not in communication with the outside.

[0086] The shelf slope portion 470 is formed in a substantially chamfered shape on one edge of the shelf portion 370, that is, on the edge of the connection portion between the shelf portion 370 and the outer shoulder land 240. The shelf slope portion 470 is a slope inclined with respect to the tire radial direction, with the groove width widening toward the outer side in the tire radial direction, and extends along the shelf portion 370.

[0087] The inner end of the shelf slope 470 in the vehicle width direction is in communication with the sub-groove 150. The outer end of the shelf slope 470 in the vehicle width direction is located midway along the outer shoulder 240, similar to the outer end of the shelf 370 in the vehicle width direction, and is not in communication with the outside.

[0088] The width of the shelf slope portion 470 in the direction perpendicular to its extension direction and its depth in the tire radial direction vary depending on its position in the extension direction. The depth of the shelf slope portion 470 can be, for example, 0.3 mm to 1.0 mm at the point of minimum depth and 3.5 mm to 7.0 mm at the point of maximum depth. The width of the shelf slope portion 470 in the direction intersecting its extension direction can be, for example, 0.5 mm to 1.5 mm at the point of minimum width and 2.5 mm to 7.0 mm at the point of maximum depth.

[0089] In the unfolded view shown in Figures 3 and 4, the fifth sipe 380 extends approximately in the direction of the tire axis, but is slightly inclined with respect to the tire axis and extends in a straight line. The inner end of the fifth sipe 380 in the vehicle width direction communicates with the sub-groove 150, and the outer end in the vehicle width direction communicates with the outer end in the tire axis direction via the end groove 381. The end groove 381 communicates with the fifth sipe 380 and the outer end in the tire axis direction, has a depth of 1 mm or less, and is wider in the direction of the outer end in the tire axis direction.

[0090] The groove width of the fifth sipe 380 may be less than 1.5 mm, but it is preferable that it be 1.0 mm or larger. The groove depth of the fifth sipe 380 can be, for example, 4.5 mm to 7.0 mm.

[0091] In the unfolded views shown in Figures 3 and 4, the sixth sipe 390 extends approximately in the direction of the tire axis, but is slightly inclined with respect to the tire axis and extends in a straight line. The inner end of the sixth sipe 390 in the vehicle width direction is located near the shelf slope portion 470, and the outer end in the vehicle width direction communicates with the outer end in the tire axis direction via the end groove 391. The end groove 391 communicates with the sixth sipe 390 and the outer end in the tire axis direction, has a depth of 1 mm or less, and is wider toward the outer side in the tire axis direction.

[0092] The groove width of the sixth sipe 390 may be less than 1.5 mm, but it is preferable that it be 1.0 mm or larger. The groove depth of the sixth sipe 390 can be, for example, 4.5 mm to 7.0 mm.

[0093] The tire 1 of this embodiment is equipped with a center width-expanding groove 510 and an outer width-expanding groove 520, which means that even as tire 1 wears down, the deterioration of drainage and traction characteristics is minimal. In other words, with relatively narrow grooves like conventional sipes, the sipes (grooves) may be temporarily blocked by tire deformation during driving, potentially resulting in insufficient drainage and traction characteristics. In contrast, in the tire 1 of this embodiment, the second wall surface 513 of the center width-expanding groove 510 and the second wall surface 523 of the outer width-expanding groove 520 are both composed of inclined surfaces that widen as they extend outward in the radial direction of the tire, thereby ensuring drainage and traction characteristics. Furthermore, since the second wall surface 513 of the center width-expanding groove 510 and the second wall surface 523 of the outer width-expanding groove 520 extend outward in the radial direction of the tire from the groove bottom 511 and groove bottom 521, respectively, the inclined surfaces do not disappear even as tire 1 wears down, thus suppressing the deterioration of drainage and traction characteristics.

[0094] Furthermore, the tire 1 of this embodiment includes a center width variable circumferential slope portion 430 and an outer width variable circumferential slope portion 450. On the side where the width of the center width variable circumferential slope portion 430 is narrower, the depth of the center width variable circumferential slope portion 430 is shallower. Therefore, a decrease in the rigidity of the second base 222 can be suppressed, and the contact pressure can be made uniform, thereby suppressing uneven wear of the second base 222. Similarly, on the side where the width of the outer width variable circumferential slope portion 450 is narrower, the depth of the outer width variable circumferential slope portion 450 is shallower. Therefore, a decrease in the rigidity of the outer shoulder base 240 can be suppressed, and the contact pressure can be made uniform, thereby suppressing uneven wear of the outer shoulder base 240.

[0095] In the tire 1 of this embodiment, the second wall surface 513 of the center width-expanding groove 510 and the second wall surface 523 of the outer width-expanding groove 520 are both linear in cross-section perpendicular to the direction of groove extension, i.e., substantially planar, as illustrated in Figures 6 and 7. However, the specific shapes of the second wall surface 513 of the center width-expanding groove 510 and the second wall surface 523 of the outer width-expanding groove 520 are not limited to flat slopes.

[0096] Figure 8 is a cross-sectional view showing a modified form of the center width widened groove 510B, in which the shape of the second wall surface 513 has been changed. Note that Figure 8 and Figure 9, which will be described later, show modified forms with the same cross-section as Figure 6. As shown in Figure 8, the second wall surface (second wall surfaces 513, 523) may be a curved surface with a convex shape directed outward in the radial direction of the tire.

[0097] Figure 9 is a cross-sectional view showing a modified form of the center width widening groove 510C, in which the shape of the second wall surface 513 has been changed. As shown in Figure 9, the second wall surface (second wall surfaces 513, 523) may be a concave curved surface directed inward in the radial direction of the tire.

[0098] The tire 1 according to the embodiment described above provides the following effects.

[0099] (1) The tire 1 according to this embodiment has groove bottoms 511, 521 with a width of less than 4 mm, first wall surfaces 512, 522 extending radially outward from the groove bottoms 511, 521, and second wall surfaces 513, 523 extending radially outward from the groove bottoms 511, 521 opposite to the first wall surfaces 512, 522, and when viewed from the radially outward side of the tire, the width of the second wall surfaces 513, 523 includes a portion that is wider than the width of the groove bottoms 511, 521, and the second wall surfaces 513, 523 are composed of inclined surfaces that are more inclined than the first wall surfaces 512, 522, and widening grooves (510, 520) that widen in the groove width toward the radially outward side of the tire extend in a direction that intersects the tire circumferential direction.

[0100] This minimizes the deterioration of drainage and traction characteristics even as tire wear progresses.

[0101] (2) The tire 1 according to this embodiment has a groove bottom 511 with a width of less than 1.5 mm, a first wall surface 512 extending from the groove bottom 511 in the tire radial direction, and a second wall surface 513 extending from the groove bottom 511 on the opposite side from the first wall surface 512 in the tire radial direction, wherein the width of the second wall surface 513 includes a portion that is wider than the width of the groove bottom 511, and the second wall surface 513 is composed of an inclined surface that is more inclined than the first wall surface 512, and a widening groove (510) that widens in the groove width toward the tire radial side extends from the groove bottom 511 in a direction that intersects the tire circumferential direction.

[0102] This minimizes the deterioration of drainage and traction characteristics even as tire wear progresses. Furthermore, by maintaining water flow paths and edges until the end of wear while maximizing the contact area, the deterioration of traction characteristics is further reduced.

[0103] (3) A tire according to (1) or (2), comprising: a plurality of main grooves (110, 120, 130) extending along the circumferential direction of the tire; an outer shoulder ridge 240 provided further outward in the vehicle width direction than the outer main groove 130, which is the outermost of the plurality of main grooves (110, 120, 130) in the vehicle width direction; and a center ridge 220 provided further outward in the vehicle width direction than the inner main groove 110, which is the innermost of the plurality of main grooves (110, 120, 130) in the vehicle width direction, and further inward in the vehicle width direction than the outer main groove 130, wherein the width-enhancing grooves (510, 520) are provided on at least one of the outer shoulder ridge 240 and the center ridge 220.

[0104] This can improve straight-line responsiveness and enhance handling stability.

[0105] (4)(3) In the tire described above, the width-enhancing grooves (510, 520) include an outer width-enhancing groove 520 provided on the outer shoulder ridge 240 and a center width-enhancing groove 510 provided on the center ridge 220, and the orientation of the first wall surface 522 and the second wall surface 523 of the outer width-enhancing groove 520 is aligned in the circumferential direction of the tire. The orientation of the first wall surface 512 and the second wall surface 513 of the center width widening groove 510 is aligned in the circumferential direction of the tire. A tire in which the orientation of the first wall surface 522 and the second wall surface 523 of the outer width-expanding groove 520 is opposite to the orientation of the first wall surface 512 and the second wall surface 513 of the center width-expanding groove 510.

[0106] This makes it possible to suppress changes in drainage characteristics and traction characteristics depending on the direction of tire rotation.

[0107] In the tire described in (5)(3) or (4), the width-expanding groove (510, 520) has an outer width-expanding groove 520 provided on the outer shoulder ridge 240 and a center width-expanding groove 510 provided on the center ridge 220, and in a cross section perpendicular to the extending direction of the width-expanding groove (510, 520), the ends of the second wall surfaces 513, 523 on the radially outer side of the tire from the intersection of the second wall surfaces 513, 523 with the groove bottoms 511, 521 If the angles formed by the line segment connecting the part and the line segment connecting the intersection of the first wall surfaces 512 and 522 with the groove bottoms 511 and 521 to the end of the first wall surface 522 on the radial side of the tire are defined as the second wall surface inclination angles θ510 and θ520, then the second wall surface inclination angle θ520 in the outer width-enlarged groove 520 is 25 degrees or more and 60 degrees or less, and the second wall surface inclination angle θ510 in the center width-enlarged groove 510 is 10 degrees or more and 40 degrees or less.

[0108] Because the angle θ510 is a relatively small angle as described above, the center width-enlarged groove 510 can effectively function as a groove. Therefore, it has a larger groove width than conventional sipes or grooves alone that do not have an inclined surface such as the second wall surface 513, and it can secure a water flow path until the end of wear, thereby improving drainage. Also, because the angle θ520 is a relatively small angle as described above, the outer width-enlarged groove 520 can effectively function as a groove. Therefore, it has a larger groove width than conventional sipes or grooves alone that do not have an inclined surface such as the second wall surface 523, and it can secure a water flow path until the end of wear, thereby improving drainage.

[0109] (6) The tire according to any of (1) to (5), having a width-dividing circumferential slope portion (430, 450) that extends in the circumferential direction of the tire and is inclined with respect to the radial direction of the tire, wherein the width in the axial direction of the tire changes gradually.

[0110] This improves the aesthetic appeal and drainage performance, while maintaining the effect of suppressing uneven wear and preventing a reduction in the contact area. Therefore, it is possible to achieve both handling stability on dry and wet surfaces.

[0111] In the tire described in (7)(6), the width-reducing circumferential slope portion (430, 450) is connected to the width-enhancing groove (510, 520).

[0112] This equalizes the ground pressure and suppresses the collapse of the blocks.

[0113] In the tire described in (8)(6) or (7), the maximum depth of the width-reducing circumferential slope portion (430, 450) is shallower than the depth of the width-expanding groove (510, 520).

[0114] This allows for more uniform contact with the ground, which helps to suppress uneven wear.

[0115] (9) In the tire described in any of (1) to (8), the second wall surfaces 513, 523 have a constant depth and, when viewed from the outside in the radial direction of the tire, their width gradually changes along the direction in which the width-expanding grooves (510, 520) extend.

[0116] This makes it possible to achieve both the effect of suppressing the deterioration of drainage and traction characteristics as tires wear down, and the effect of enhancing the aesthetic design.

[0117] The present invention is not limited to the embodiments described above, and various modifications and changes are possible, all of which fall within the scope of this disclosure. [Explanation of symbols]

[0118] 1 tire 30 tread 36 Tread Rubber 37 Tread surface 38 Tread Pattern 40 Shoulder 40A Inner Shoulder 40B External Shoulder 100 Main groove 110 Inner main groove 111 Inner circumferential slope section 120 Intermediate main groove 121 Intermediate circumferential slope section 130 Outer main groove 150 secondary grooves 200 land 210 Inner Shoulder Land 220 Center Athletics 221 First Land 222 Second Land 240 Outer shoulder land 310 First Sipe 320 Second Sipe 321 End groove 322 End groove 330 Third Sipe 350 Fourth Sipe 370 Shelf 380 Fifth Sipe 381 End groove 390 Sixth Sipe 391 End groove 410, 420 Third sipe slope section 430 Center width variable circumferential slope section 450 Outside width deviation circumferential slope section 470 Shelf slope section 510, 510B, 510C Center width widened groove 511 Groove bottom 512 First Wall 513, 513B, 513C Second wall 520 Outer width widening groove 521 Groove bottom 522 First Wall 523 Second Wall

Claims

1. Groove bottoms with a width of less than 4 mm, A first wall surface extending radially outward from the bottom of the groove, A second wall surface extending radially outward from the opposite side of the first wall surface at the bottom of the groove, It has, When viewed from the outside in the radial direction of the tire, the width of the second wall surface includes a portion that is wider than the width of the groove bottom. A tire in which the second wall surface is composed of an inclined surface that is more inclined than the first wall surface, and a widening groove extends from the bottom of the groove toward the radially outward direction of the tire, with the groove width increasing in a direction that intersects the circumferential direction of the tire.

2. Groove bottoms with a width of less than 1.5 mm, A first wall surface extending from the bottom of the groove in the radial direction of the tire, A second wall surface extending in the tire radial direction from the opposite side of the groove bottom from the first wall surface, It has, When viewed from the outside in the radial direction of the tire, the width of the second wall surface includes a portion that is wider than the width of the groove bottom. A tire in which the second wall surface is composed of an inclined surface that is more inclined than the first wall surface, and a widening groove extends from the bottom of the groove toward the radially outward direction of the tire, with the groove width increasing in a direction that intersects the circumferential direction of the tire.

3. In the tire according to claim 1 or claim 2, Multiple main grooves extending along the circumferential direction of the tire, An outer shoulder land is provided further outward in the vehicle width direction than the outer main groove, which is the outermost of the multiple main grooves in the vehicle width direction, A center ramp is provided that is located further outward in the vehicle width direction than the inner main groove, which is the innermost of the multiple main grooves in the vehicle width direction, and further inward in the vehicle width direction than the outer main groove, Equipped with, The widening groove is provided on at least one of the outer shoulder land and the center land of the tire.

4. In the tire described in claim 3, The aforementioned widened groove is The outer width widening groove provided on the outer shoulder land, The aforementioned center width widening groove provided on the center land, It has, The orientation of the first and second wall surfaces of the outer width-enlarged groove is aligned in the circumferential direction of the tire. The orientation of the first and second wall surfaces of the center width widening groove is aligned in the circumferential direction of the tire. A tire in which the orientation of the first and second wall surfaces of the outer width-enhancing groove is opposite to the orientation of the first and second wall surfaces of the center width-enhancing groove.

5. In the tire described in claim 3, The aforementioned widened groove is The outer width widening groove provided on the outer shoulder land, The aforementioned center width widening groove provided on the center land, It has, In a cross-section perpendicular to the direction of extension of the widening groove, If the angle between the line segment connecting the intersection of the second wall surface with the groove bottom to the end of the second wall surface on the radially outer side of the tire, and the line segment connecting the intersection of the first wall surface with the groove bottom to the end of the first wall surface on the radially outer side of the tire, then the second wall surface inclination angle is defined as follows: The inclination angle of the second wall surface in the outer width-enlarged groove is 25 degrees or more and 60 degrees or less. A tire in which the inclination angle of the second wall surface in the center width widening groove is 10 degrees or more and 40 degrees or less.

6. In the tire according to claim 1 or claim 2, A tire having a width-variable circumferential slope portion that extends in the circumferential direction of the tire and is inclined with respect to the radial direction of the tire, wherein the width in the axial direction of the tire gradually changes.

7. In the tire according to claim 6, The aforementioned width-reducing circumferential slope portion is connected to the width-enhancing groove, in a tire.

8. In the tire according to claim 6, A tire in which the maximum depth of the width-reducing circumferential slope portion is shallower than the depth of the width-enhancing groove.

9. In the tire according to claim 1 or claim 2, The second wall surface has a constant depth, and when viewed from the outside in the radial direction of the tire, its width gradually changes along the direction in which the width-expanding groove extends.

Images