pneumatic tires

Abstract

The present invention provides a pneumatic tire that makes deformation of the buttress more likely to occur regardless of whether the tire is rolling in either direction, thereby reducing wear on the shoulder area. [Solution] The tire comprises a tread 30 including a tread surface 32 that contacts the road surface and a pair of shoulder blocks 84 provided at both ends of the tread surface 32 in the tire axial direction, a pair of sidewalls 20 that form the outer surface 2 of the tire, a pair of buttresses 40 provided between the shoulder blocks 84 and the sidewalls 20, and a belt 34 within the tread 30 that is positioned on the inner side of the buttresses 40 in the tire axial direction, wherein the buttresses 40 include a plurality of buttress grooves 100 arranged in the circumferential direction of the tire, the buttress grooves 100 extending inclined with respect to the tire radial direction such that their inner ends in the tire radial direction approach each other as they move inward in the tire radial direction, and a pair of first grooves 110 arranged on both sides of a virtual line L1 along the tire radial direction.

Description

Technical Field

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

[0002] Generally, in a pneumatic tire, wear is likely to occur in a shoulder portion where the contact pressure increases when the vehicle turns. For example, Patent Document 1 discloses a tire in which a plurality of linear grooves inclined in the same direction with respect to the tire radial direction are provided parallel to each other along the tire circumferential direction in a portion called a buttress between a shoulder rib and a sidewall, thereby reducing the rigidity of the buttress to cause a reduction in the contact pressure applied to the shoulder rib, and consequently suppressing wear of the shoulder rib. Prior Art Literature Patent Literature

[0003] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2014-218245 Summary of the Invention Problem to be Solved by the Invention

[0004] In the tire disclosed in the above Patent Document 1, since the plurality of grooves provided in the buttress are linear grooves inclined in the same direction, the buttress is easily deformed in one direction of the tire rolling direction and contributes to reduction in rigidity, but it is assumed that the buttress is less likely to be deformed when the tire rolls in the direction opposite to that direction.

[0005] Therefore, an object of the present invention is to provide a pneumatic tire that can reduce wear of a shoulder portion by facilitating deformation of the buttress regardless of whether the rolling direction of the tire is either of two directions. Means for Solving the Problem

[0006] The pneumatic tire of the present invention comprises a tread including a tread surface that contacts the road surface and a shoulder portion provided at the axial end of the tread surface, a sidewall forming the outer surface of the tire, a buttress provided between the shoulder portion and the sidewall, and a belt within the tread, disposed on the axial side of the buttress, wherein the buttress includes a plurality of buttress grooves arranged in the circumferential direction of the tire, the buttress grooves extend inclined with respect to the tire radial direction such that their radially inner ends approach each other as they move radially inward, and have a pair of first grooves arranged on both sides of a virtual line along the tire radial direction. [Effects of the Invention]

[0007] According to the present invention, a pneumatic tire can be provided that reduces wear on the shoulder portion by making the buttress more susceptible to deformation regardless of whether the tire is rolling in either direction. [Brief explanation of the drawing]

[0008] [Figure 1] This is a half-cross-sectional view of the tire in the axial direction according to the embodiment. [Figure 2] This is an unfolded view showing a portion of the tread and buttress of the tire according to the embodiment, laid out in a planar shape. [Figure 3] This is a view from arrow III in Figure 1. [Figure 4] This diagram schematically shows the deformation of the rubber in the buttress due to the buttress groove according to the embodiment. [Figure 5A] Figure 3 is a VA-VA cross-sectional view. [Figure 5B] Figure 3 is a VB-VB cross-sectional view. [Figure 6] This figure corresponds to Figure 5A and is a cross-sectional view showing a modified example in which the bottom of the connecting groove is flat. [Figure 7] This diagram schematically shows the deformation of the rubber in the buttress caused by the buttress groove in the modified version. [Modes for carrying out the invention]

[0009] The embodiments will be described below with reference to the drawings. Figure 1 is a diagram showing the internal structure of tire 1, which is a pneumatic tire according to the embodiment, and is a half-cross-sectional view showing the right half. Figure 2 is a diagram showing a part of the tire circumferential direction of the tread 30 and buttress 40 of tire 1, which will be described later, unfolded in a planar manner, and is an unfolded view of the right half. Figure 3 is a view taken along arrow III in Figure 1.

[0010] The tire 1 according to this embodiment is, for example, a pneumatic tire for a truck. The configuration of the tire 1 according to this embodiment can be used for various vehicles other than trucks, such as light trucks, buses, and passenger cars.

[0011] The cross-sectional view in Figure 1 is a half-section view of the tire in the axial direction (tire meridian half-section view) under no-load conditions, with tire 1 mounted on a standard rim (not shown) and filled to the standard internal pressure. The standard rim is the rim specified for each tire in the standard system that includes 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 that includes 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.

[0012] In Figures 1 and 2, the symbol S represents the tire equatorial plane. The tire equatorial plane S is a plane perpendicular to the tire rotation axis (tire meridian) and is located at the center of the tire axial direction. The basic internal structure of tire 1 is symmetrical in the tire axial direction cross-section with respect to the tire equatorial plane S.

[0013] Here, the tire axis direction is the direction parallel to the tire rotation axis, which is the left-right direction in the cross-sectional view of Figure 1. In Figure 1, the tire axis direction is indicated by arrow X. The inner direction in the tire axis direction is the direction approaching the tire equatorial plane S, which is the left side of the paper in Figure 1. The outer direction in the tire axis direction is the direction away from the tire equatorial plane S, which is the right side of the paper in Figure 1. The tire radial direction is the direction perpendicular to the tire rotation axis, which is the up-down direction in the paper in Figure 1. In Figure 1, the tire radial direction is indicated by arrow Y. The outer direction in the tire radial direction is the direction away from the tire rotation axis, which is the top side of the paper in Figure 1. The inner direction in the tire radial direction is the direction approaching the tire rotation axis, which is the bottom side of the paper in Figure 1. Note that in Figure 2, the tire circumferential direction is indicated by arrow C along with the tire axis direction X and tire radial direction Y. Also, in Figure 3, the tire radial direction Y and tire circumferential direction C are shown.

[0014] The tire 1 comprises a pair of beads 10 provided on both sides of the tire axial direction, a pair of sidewalls 20 extending radially outward from each of the pair of beads 10, a tread 30 positioned between the pair of sidewalls 20, a buttress 40 positioned between the sidewalls 20 and the tread 30, a carcass ply 50 positioned between the pair of beads 10, and an inner liner 60 positioned on the inner side of the carcass ply 50.

[0015] The bead 10 includes a bead core 11, a bead filler 12 extending radially outward from the bead core 11, a chaff 13, and a rim strip rubber 14.

[0016] The bead core 11 is an annular component formed by winding a rubber-coated metal bead wire multiple times, and it serves to secure the air-filled tire 1 to the rim.

[0017] The bead filler 12 is a rubber member that tapers as it extends outward in the tire radial direction. The bead filler 12 is a member provided to increase the rigidity of the peripheral portion of the bead 10 and ensure high maneuverability and stability. The bead filler 12 is made of, for example, rubber having higher hardness than surrounding rubber members.

[0018] The chafer 13 is provided inward in the tire radial direction of the carcass ply 50 disposed around the bead core 11.

[0019] The rim strip rubber 14 is disposed outward in the tire axial direction of the chafer 13 and the carcass ply 50. The rim strip rubber 14 is a member that contacts an unillustrated rim on which the tire 1 is mounted.

[0020] The sidewall 20 includes a sidewall rubber 21 disposed outward in the tire axial direction of the carcass ply 50. The sidewall rubber 21 forms the outer side surface of the tire 1. An inner end 21a of the sidewall rubber 21 in the tire radial direction extends inward in the tire radial direction and covers an outer portion of the rim strip rubber 14 in the tire radial direction. The sidewall rubber 21 is the portion that deflects the most when the tire 1 exerts a cushioning effect, and a flexible rubber having fatigue resistance is normally used therefor.

[0021] A first pad rubber 15 is disposed between the bead filler 12, the sidewall rubber 21 and the rim strip rubber 14.

[0022] The tread 30 includes a belt 34, a cap ply 37, and a tread rubber 31. The belt 34 is disposed outward in the tire radial direction of the carcass ply 50. The cap ply 37 is disposed outward in the tire radial direction of the belt 34.

[0023] The belt 34 is a member that reinforces the tread 30. The belt 34 in this embodiment has a two-layer structure comprising a first belt 35 positioned on the outer side of the inner liner 60 in the tire radial direction, and a second belt 36 positioned on the outer side of the first belt 35 in the tire radial direction. Both the first belt 35 and the second belt 36 have a structure in which multiple belt cords, such as steel cords, are covered with rubber. The second belt 36 is wider than the first belt 35. Therefore, the belt end 34a, which is the outer end of the belt 34 in the tire axial direction, is the outer end of the second belt 36 in the tire axial direction. By providing the belt 34, the rigidity of the tire 1 is ensured, and the contact of the tread 30 with the road surface is improved. Note that the belt 34 is not limited to a two-layer structure, but may have a single layer or a structure of three or more layers.

[0024] The cap ply 37 is positioned on the outer side of the belt 34 in the tire radial direction. The cap ply 37 has a structure in which multiple insulating organic fiber cords, such as polyamide fibers, are covered with rubber. The cap ply 37 in this embodiment has a two-layer structure comprising a first cap ply 38 positioned on the outer side of the second belt 36 in the tire radial direction, and a second cap ply 39 positioned on the outer side of the first cap ply 38 in the tire radial direction. The cap ply 37 is a member that reinforces the tread 30 together with the belt 34. By providing the cap ply 37, durability can be improved and road noise during driving can be reduced. Note that the cap ply 37 is not limited to a two-layer structure, but may have a single layer or a structure of three or more layers.

[0025] The tread rubber 31 is positioned radially outward of the cap ply 37. The tread rubber 31 has a tread surface 32 which is the outer surface of the tread 30 and the tire 1 makes contact with the road surface.

[0026] As shown in Figures 1 and 2, the tread surface 32 has one main groove 71 and one secondary groove 72 on the left and right sides of the tire's equatorial plane S. The main groove 71 and secondary groove 72 are annular grooves that are continuous in the circumferential direction of the tire. The main groove 71 is located on the side of the tire's equatorial plane S, and the secondary groove 72 is located on the axial side of the main groove 71. As shown in Figure 2, the main groove 71 has a zigzag shape. The secondary groove 72 is a groove with a smaller groove width than the main groove 71 and is a straight groove along the circumferential direction of the tire.

[0027] The tread 30 includes a central tread 81, a pair of intermediate treads 82 on either side of the central tread 81 in the tire axial direction, and a pair of shoulder treads 83 on the tire axial side of each intermediate tread 82. The central tread 81 is located between a pair of main grooves 71 that straddle the tire equatorial plane S. Each intermediate tread 82 is located between the main groove 71 and a secondary groove 72 adjacent to the tire axial side of the main groove 71. The shoulder treads 83 are located at both ends of the tire axial direction, in the portions that are tire axially outward of the secondary grooves 72.

[0028] As shown in Figure 2, the shoulder base 83 has a plurality of shoulder blocks 84. The shoulder blocks 84 constitute the shoulder portion. The shoulder base 83 has a plurality of lug grooves 85 extending in the tire axial direction, formed at approximately equal pitches in the tire circumferential direction. The shoulder blocks 84 are formed between pairs of adjacent lug grooves 85 in the tire circumferential direction.

[0029] As shown in Figure 2, the intermediate ridge 82 has a plurality of slits 73 that connect the main groove 71 and the sub-groove 72. The slits 73 are linear grooves that intersect the tire circumferential direction and are inclined with respect to the tire axial direction. The plurality of slits 73 are arranged at approximately equal pitches around the entire circumference of the tire in the circumferential direction. Each slit 73 is positioned correspondingly between a pair of adjacent lug grooves 85 in the circumferential direction of the tire.

[0030] As shown in Figure 1, the buttress 40 is provided between the shoulder block 84 and the sidewall 20. The buttress 40 forms the outer surface 2 of the tire, continuous with the sidewall 20. The buttress 40 is the annular portion on the radially outer side of the outer surface 2 of the tire. A shoulder 86 is formed between the buttress 40 and the shoulder block 84 of the tread 30, forming a nearly right angle in the axial cross-section of the tire. The belt 34 is located within the tread 30 and on the axially inner side of the buttress 40.

[0031] The buttress 40 includes a plurality of buttress grooves 100 arranged at approximately equal pitches in the circumferential direction of the tire. In this embodiment, the buttress grooves 100 are formed in a substantially X shape when viewed from the side (viewed as arrow III in Figure 1). The buttress grooves 100 are located on the outer side of the belt 34 in the tire axial direction. Details of the buttress grooves 100 will be described later.

[0032] As shown in Figure 1, the carcass ply 50 is stretched between a pair of beads 10. The carcass ply 50 constitutes the skeletal ply of the tire 1. The carcass ply 50 is embedded in the tire 1 in such a manner that it passes between the pair of beads 10, through a pair of sidewalls 20, a pair of buttresses 40, a pair of shoulders 86, and the inner side of the tread 30. On the tread 30, a belt 34, a cap ply 37, and tread rubber 31 are arranged on the radially outer side of the carcass ply 50.

[0033] The carcass ply 50 has a ply body portion 51 between a pair of bead cores 11, and a pair of folded portions 52 that are folded back from the inner end of the ply body portion 51 in the tire radial direction around each bead core 11 and extend radially outward on the tire axial side of each bead filler 12.

[0034] A second pad 16 is embedded in the outer surface side of the carcass ply 50 in the part of tire 1 that corresponds to the shoulder 86.

[0035] The carcass ply 50 in this embodiment has a single-layer structure consisting of one carcass ply layer, but it may also have a two-layer structure or a more than two-layer structure.

[0036] The inner liner 60 covers the inner surface of the ply body portion 51 of the carcass ply 50 between the pair of beads 10. The inner liner 60 is made of air-permeable rubber to prevent air inside the tire cavity from leaking to the outside.

[0037] The above describes the internal structure of the tire 1 according to the embodiment. Next, the buttress groove 100 provided in the buttress 40 will be described.

[0038] As shown in Figure 2, the lug groove 85 extends from the shoulder block 83 through the shoulder 86 to the radially outer portion of the buttress 40. The buttress grooves 100 are positioned one at a time at the positions corresponding to each shoulder block 84, and between pairs of adjacent lug grooves 85 in the circumferential direction of the tire.

[0039] As shown in Figure 3, the buttress groove 100 has a pair of first grooves 110, a pair of second grooves 120, and a connecting groove 130.

[0040] Each of the pair of first grooves 110 is linear and extends at an inclination with respect to the tire radial direction such that the inner ends 111 in the tire radial direction move closer to each other as they move inward in the tire radial direction. In other words, each of the pair of linear first grooves 110 extends at an inclination with respect to the tire radial direction such that the outer ends 112 in the tire radial direction move further apart from each other as they move outward in the tire radial direction. The pair of first grooves 110 are aligned in the tire circumferential direction. The pair of first grooves 110 are positioned on both sides of a virtual line L1 along the tire radial direction and have a symmetrical pattern shape with respect to the virtual line L1 as the line of symmetry.

[0041] A pair of second grooves 120 are positioned radially inward of a pair of first grooves 110. Each of the pair of second grooves 120 is linear and extends inclined with respect to the tire radial direction such that their radially outer ends 121 move closer together as they move radially outward. In other words, each of the linear pair of second grooves 120 extends inclined with respect to the tire radial direction such that their radially inner ends 122 move further apart as they move radially inward. The pair of second grooves 120 are aligned in the circumferential direction of the tire. The pair of second grooves 120 are positioned on both sides of a virtual line L1 along the tire radial direction and have a symmetrical pattern shape with respect to the virtual line L1 as the line of symmetry.

[0042] The inner ends 111 of the pair of first grooves 110 in the tire radial direction and the outer ends 121 of the pair of second grooves 120 in the tire radial direction are close together in the tire radial direction. The connecting groove 130 is a groove that connects the inner ends 111 of the pair of first grooves 110 in the tire radial direction and the outer ends 121 of the pair of second grooves 120 in the tire radial direction. The connecting groove 130 is linear and is located on a virtual line L1 along the tire radial direction. Therefore, the buttress groove 100 as a whole has a symmetrical pattern shape with the virtual line L1 along the tire radial direction as the line of symmetry.

[0043] As shown in Figure 1, in the tire axial cross-section, the distance L2 between the groove bottom 135 of the connecting groove 130 and the belt end 34a is 8 mm or more. As shown in Figure 1, in the tire axial cross-section, the groove bottom 135 of the connecting groove 130 is formed in an arc shape that is convex outward in the tire axial direction. The groove bottom 135 of the connecting groove 130 follows an arc 140 centered on the belt end 34a, and is located on or outward in the tire axial direction from the arc 140. The radius of the arc 140 here is set to the above distance L2, which is 8 mm. That is, in the tire axial cross-section, the arc-shaped groove bottom 135 of the connecting groove 130 is located on or outward in the tire axial direction from the arc 140 with a radius of 8 mm centered on the belt end 34a.

[0044] According to the embodiment of tire 1, the buttress 40 having the buttress groove 100 has moderately reduced rigidity compared to the case without the buttress groove 100. Figure 4 schematically shows the deformation of the rubber in the buttress 40 caused by the buttress groove 100. In Figure 4, the left diagram shows the state in which the tire 1 is in contact with the road surface R in a stationary state, and then shows the case when the tire 1 rotates while moving forward, and external forces indicated by arrows are applied to the buttress 40 from the left side in the direction of travel and from above.

[0045] As shown in the right-hand diagram of Figure 4, when the buttress 40 is subjected to an external force, the rubber of the pair of first grooves 110, specifically the one on the direction of travel (front side), flexes so that it bulges, and the rubber of the pair of second grooves 120, specifically the one on the opposite side of the direction of travel (rear side), bulges. Furthermore, the rubber of the connecting groove 130 bulges. The presence of the first groove 110, second groove 120, and connecting groove 130 reduces the rigidity of the buttress 40, causing the rubber of the buttress 40 to deform in this manner. On the other hand, when the tire 1 rotates while the vehicle is moving forward in the opposite direction to the direction of travel, the rubber of the buttress 40 deforms in the opposite direction, and the pair of first grooves 110 and the pair of second grooves 120 bulge, as opposed to the right-hand diagram of Figure 4, as the rubber of the right-hand first groove 110 and the left-hand second groove 120 bulges, and furthermore, the rubber of the connecting groove 130 bulges. Furthermore, due to differences in the mounting position of the tire 1 on the left and right sides of the vehicle, and by performing tire rotation, the direction of rotation of the tire 1 when moving forward is reversed. Therefore, in the case of the tire 1, deformation is likely to occur in the buttress 40 regardless of whether the direction of rotation is bidirectional. As a result, the ground pressure on the shoulder block 84 is reduced, and the wear of the shoulder block 84 is suppressed. In particular, when the vehicle is turning, the wear of the shoulder block 84 on the outside of the turn is suppressed.

[0046] The buttress grooves 100 increase the surface area of ​​the rubber, thereby enhancing the heat dissipation of the rubber of the tire 1. Therefore, the heat dissipation of the buttress grooves 100 is higher if the groove depth is deep and it is close to the heat source, or if the groove width is large. In the tire 1 according to this embodiment, the belt 34 is located within the tread 30 and on the inner side of the buttress 40 in the tire axial direction. That is, the buttress 40 is located on the outer side of the belt 34 in the tire axial direction, and the buttress grooves 100 are arranged on the buttress 40. As a result, the heat generated near the belt 34, especially near the belt end 34a, during driving is easily dissipated by the buttress grooves 100. Therefore, failures such as cracks caused by high heat of the rubber near the belt 34, especially near the belt end 34a, are suppressed.

[0047] Figure 5A is a cross-sectional view taken along the line VA-VA in Figure 3. In this embodiment, it is preferable that the groove depth of the first groove 110 and the second groove 120 gradually increases from the outer end 112 and the inner end 122 in the radial direction of the tire toward the connecting groove 130, respectively. This suppresses stone jamming, where stones remain trapped in the first groove 110 and the second groove 120. Note that the groove depth of the first groove 110 and the second groove 120 may be configured such that at least one of them gradually increases toward the connecting groove 130.

[0048] Here, if the groove width of the first groove 110, the second groove 120, and the connecting groove 130 on the tire surface is less than 3 mm, the reduction in rigidity of the buttress 40 will be insufficient. On the other hand, if it exceeds 8 mm, the rigidity will be excessively reduced, potentially causing cracks in the buttress 40. Therefore, the groove width of the first groove 110, the second groove 120, and the connecting groove 130 on the tire surface is preferably 3 mm or more and 8 mm or less, and more preferably 4.5 mm or more and 6.5 mm or less. In this specification, groove width refers to the distance between one groove edge and the other groove edge in a direction perpendicular to the direction in which the groove extends.

[0049] Furthermore, it is preferable that the groove width at the bottom of the first groove 110, the second groove 120, and the connecting groove 130 is smaller than the groove width on the tire surface. Figure 5B is a VB-VB cross-sectional view of Figure 3, and as a representative example, it shows that the groove width W110a at the bottom 115 of the first groove 110 is smaller than the groove width 110b on the tire surface.

[0050] Here, if the groove width at the bottom of the first groove 110, the second groove 120, and the connecting groove 130 is less than 1 mm, the reduction in rigidity of the buttress 40 will be insufficient. On the other hand, if it is greater than 5 mm, the rigidity will be excessively reduced, which may cause cracks in the buttress 40. Therefore, the groove width at the bottom of the first groove 110, the second groove 120, and the connecting groove 130 is preferably 1 mm or more and 5 mm or less, and more preferably 2 mm or more and 4 mm or less.

[0051] As shown in Figure 1, in the tire 1 of this embodiment, the connecting groove 130 is located on the tire axial line L3 passing through the belt end 34a in the tire axial cross-section. The first angle θ1 formed by the tire axial line L3 and the line L4 connecting the outer end 112 in the tire radial direction of the first groove 110 and the belt end 34a is preferably 20° or more and 40° or less, and more preferably 25° or more and 35° or less. In addition, in the tire 1 of this embodiment, the second angle θ2 formed by the tire axial line L3 passing through the belt end 34a and the line L5 connecting the inner end 122 in the tire radial direction of the second groove 120 and the belt end 34a is preferably 20° or more and 40° or less, and more preferably 25° or more and 35° or less. If the angles θ1 and θ2 are less than 20°, the groove length will be insufficient, and it will be difficult to obtain the wear suppression effect of the shoulder block 84. On the other hand, if the angles θ1 and θ2 mentioned above exceed 40°, the groove length becomes excessively large and the rigidity decreases excessively, increasing the likelihood of cracks occurring in the buttress 40.

[0052] As shown in Figure 2, the overall width W1 of the buttress groove 100 is preferably about 2 / 5 of the width W2 of one shoulder block 84. That is, for example, if the width W2 of the shoulder block 84 is about 50 mm, the overall width W1 of the buttress groove 100 is preferably about 20 mm. Note that in this case, width refers to the tire circumferential length.

[0053] As shown in Figure 2, the overall height H1 (tire radial length) of the buttress groove 100 is preferably about 3 / 5 of the width W2 (tire circumferential length) of one shoulder block 84. That is, for example, if the width W2 of the shoulder block 84 is about 50 mm, the overall height H1 of the buttress groove 100 is preferably about 20 mm.

[0054] As shown in Figure 1, the radially outer end 112 of the first groove 110 is located radially outward from the belt end 34a. As shown in Figure 2, the distance L6 from the radially outer end 112 of the first groove 110 to the axially outer end 30a of the tread 30 is preferably about 3 / 10 of the width W2 of the shoulder block 84. That is, for example, if the width W2 of the shoulder block 84 is about 50 mm, the distance L6 is preferably about 15 mm.

[0055] The tire 1 of the above embodiment provides the following effects.

[0056] (1) The tire 1 according to the embodiment is a pneumatic tire comprising: a tread 30 including a tread surface 32 that contacts the road surface and shoulder blocks 84 provided at the tire axial end of the tread surface 32; a pair of sidewalls 20 that form the outer surface 2 of the tire; a pair of buttresses 40 provided between the shoulder blocks 84 and the sidewalls 20; and a belt 34 within the tread 30, arranged inward from the tire axial side of the buttresses 40, wherein the buttresses 40 include a plurality of buttress grooves 100 arranged in the tire circumferential direction, the buttress grooves 100 extending inclined with respect to the tire radial direction such that the radially inner ends 111 of the tire approach each other as they move inward in the tire radial direction, and having a pair of first grooves 110 arranged on both sides of a virtual line L1 along the tire radial direction.

[0057] As a result, deformation is more likely to occur in the buttress 40 regardless of whether the rolling direction is bidirectional, thus reducing the contact pressure on the shoulder block 84 when the tire 1 rotates, and suppressing wear of the shoulder block 84. In addition, heat generated near the belt 34 during driving is easily dissipated by the buttress groove 100, suppressing failures such as cracks caused by overheating of the rubber near the belt 34.

[0058] (2) In the tire 1 of the embodiment described in (1) above, the buttress groove 100 further comprises a pair of second grooves 120 arranged on the inside of a pair of first grooves 110 in the tire radial direction, extending inclined with respect to the tire radial direction such that the outer ends in the tire radial direction approach each other as they move outward in the tire radial direction, and arranged on both sides of a virtual line L1 along the tire radial direction.

[0059] By further including the second groove 120 in this manner, the effect of suppressing wear of the shoulder block 84 due to the reduction in rigidity of the buttress 40, as well as the heat dissipation effect of the buttress groove 100, are further enhanced.

[0060] (3) In the tire 1 according to the embodiment described in (2), the buttress groove 100 further has a connecting groove 130 that connects the inner ends 111 in the tire radial direction of a pair of first grooves 110 and the outer ends 121 in the tire radial direction of a pair of second grooves 120.

[0061] By further providing the connecting groove 130, the effect of suppressing wear of the shoulder block 84 due to the reduction in rigidity of the buttress 40, as well as the heat dissipation effect of the buttress groove 100, are further enhanced. In addition, the connecting groove 130 alleviates stress concentration at the inner end 111 of the first groove 110 in the tire radial direction and the outer end 121 of the second groove 120 in the tire radial direction, thereby suppressing the occurrence of cracks in the buttress 40 and maintaining the shape of the buttress groove 100.

[0062] (4) In the tire 1 according to the embodiment described in (3) above, it is preferable that the groove bottom 135 of the connecting groove 130 and the belt end 34a, which is the outer end of the belt 34 in the tire axial direction, are spaced 8 mm or more apart in the tire axial cross section.

[0063] This makes it difficult for stress from the belt 34 to be transmitted to the connecting groove 130 of the buttress groove 100, thereby suppressing the occurrence of cracks in the buttress 40.

[0064] (5) In the tire 1 according to the embodiments of (3) and (4) above, in the tire axial cross section, the groove bottom 135 of the connecting groove 130 has a convex arc shape outward in the tire axial direction, and it is preferable that the groove bottom 135 is located on or outward in the tire axial direction from the arc 140 with a radius of 8 mm centered on the belt end 34a.

[0065] This makes it difficult for stress from the belt 34 to be transmitted to the connecting groove 130 of the buttress groove 100, thereby suppressing the occurrence of cracks in the buttress 40.

[0066] (6) In the tire 1 according to the embodiment described in (3) to (5) above, it is preferable that at least one of the first groove 110 and the second groove 120 has a groove depth that gradually increases toward the connecting groove 130.

[0067] This suppresses stone jamming in the first groove 110 and / or the second groove 120, which have progressively increasing groove depths toward the connecting groove 130.

[0068] (7) In the tire 1 according to the embodiment described in (3) to (6) above, the groove width of the first groove 110, the second groove 120 and the connecting groove 130 on the tire surface is preferably 3 mm or more and 8 mm or less.

[0069] This suppresses the occurrence of cracks in the buttress 40, while also reducing the contact pressure on the shoulder block 84 when the tire 1 rotates, thereby suppressing wear on the shoulder block 84.

[0070] (8) In the tire 1 according to the embodiment described in (3) to (7) above, the groove width at the bottom of the first groove 110, the second groove 120 and the connecting groove 130 is preferably smaller than the groove width on the tire surface and is 1 mm or more and 5 mm or less.

[0071] This prevents stones from getting stuck in the first groove 110, the second groove 120, and the connecting groove 130, as well as prevents mud from clogging.

[0072] (9) In the tire 1 according to the embodiment described in (3) to (7) above, in the tire axial cross section, the first angle θ1 formed by the tire axial line L3 passing through the belt end 34a, which is the outer end of the belt 34 in the tire axial direction, and the line L4 connecting the outer end 112 in the tire radial direction of the first groove 110 and the belt end 34a is preferably 20° or more and 40° or less, and the second angle θ2 formed by the tire axial line L3 passing through the belt end 34a and the line L5 connecting the inner end 122 in the tire radial direction of the second groove 120 and the belt end 34a is preferably 20° or more and 40° or less.

[0073] This improves the heat dissipation of the belt end 34a by the first groove 110 and second groove 120 of the buttress groove 100, thereby suppressing failures such as cracks caused by overheating of the rubber near the belt end 34a.

[0074] Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., made to the extent that the objectives of the present invention can be achieved are also included within the scope of the present invention.

[0075] For example, as shown in Figure 6, the groove bottom 135 of the connecting groove 130 is not formed in a convex arc shape outward in the tire axial direction, but may be planar in the direction of the tire axial direction and the tire radial direction. In this case, it is preferable that the groove bottom 135 is further outward in the tire axial direction than the arc-shaped groove bottom 135 of the above embodiment, and that the distance between it and the belt end 34a is 8 mm or more.

[0076] Furthermore, for example, the buttress groove 100 may not have a connecting groove 130, but instead have a pair of first grooves 110 and a pair of second grooves 120. Alternatively, it may consist of at least a pair of first grooves 110 alone. Even in this case, the effect of suppressing wear of the shoulder block 84 due to the reduction in rigidity of the buttress 40, as well as the heat dissipation effect of the buttress groove 100, can be obtained.

[0077] Figure 7 is a diagram corresponding to Figure 4, and schematically shows the deformation of the rubber in the buttress 40 by a modified buttress groove 100 that does not have a connecting groove 130 and is composed of a pair of first grooves 110 and a pair of second grooves 120. In the modified buttress groove 100, the inner ends of the pair of first grooves 110 in the tire radial direction are connected, and the outer ends of the pair of second grooves 120 in the tire radial direction are connected, and furthermore, the inner ends of the connected pair of first grooves 110 in the tire radial direction and the outer ends of the connected pair of second grooves 120 in the tire radial direction are connected. Therefore, the modified buttress groove 100 has a simple X shape.

[0078] Figure 7 shows the case where, starting from the left diagram which assumes the tire 1 is in contact with the road surface R in a stationary state, the tire 1 rotates during forward movement, and external forces, indicated by arrows, are applied to the buttress 40 from the left side (direction of travel) and above. As shown in the right diagram of Figure 7, when the buttress 40 is subjected to external forces, the rubber of the pair of first grooves 110, specifically the first groove 110 on the direction of travel side (front) and the second groove 120 which communicates with this first groove 110 and is on the opposite side of the direction of travel (rear), flexes so that it bulges. On the other hand, when the vehicle tire 1 rotates while the vehicle is moving forward in the opposite direction to the direction of travel, the rubber of the buttress 40 deforms in the opposite direction, and the pair of first grooves 110 and the pair of second grooves 120 flex so that the right first groove 110 and the left second groove 120 bulge, contrary to the right diagram of Figure 7. Therefore, in the tire 1, deformation is likely to occur in the buttress 40 regardless of whether the rolling direction is bidirectional. As a result, when tire 1 rotates, the contact pressure on the shoulder block 84 is reduced, and wear of the shoulder block 84 is suppressed. In this case, in particular when the vehicle is turning, wear of the shoulder block 84 on the outside of the turn is suppressed.

[0079] In the buttress groove 100, the ends of the grooves, such as the outer end 112 of the first groove 110 in the tire radial direction and the inner end 122 of the second groove 120 in the tire radial direction, may be formed in an R shape. This configuration reduces stress concentration at the ends of these grooves, thereby suppressing the occurrence of cracks originating from the ends and maintaining the shape of the buttress groove 100.

[0080] Furthermore, in the buttress groove 100, the portion of the inner corner formed between the groove bottom and the groove wall rising from the groove bottom should be formed to transition smoothly in an R shape. [Explanation of symbols]

[0081] 1...Tire (pneumatic tire), 2...Outer surface of tire, 20...Sidewall, 30...Tread, 32...Tread surface, 34...Belt, 34a...Belt end, 40...Buttress, 84...Shoulder block (shoulder section), 100...Buttress groove, 110...First groove, 120...Second groove, 130...Connecting groove, 135...Bottom of connecting groove, 140...Circular arc, L1...Imaginary line along the radial direction of the tire, θ1...First angle, θ2...Second angle.

Claims

1. The tread includes a tread surface that contacts the road surface and a shoulder portion provided at the axial end of the tread surface, The sidewall that forms the outer surface of the tire, A buttress is provided between the shoulder portion and the side wall, A pneumatic tire comprising a belt located within the tread and positioned axially inward of the buttress, The buttress includes a plurality of buttress grooves arranged in the circumferential direction of the tire, A pneumatic tire having a pair of first grooves arranged on both sides of a virtual line along the tire's radial direction, wherein the buttress groove extends inclined with respect to the tire's radial direction such that its inner ends in the tire's radial direction approach each other as it moves inward in the tire's radial direction.

2. The pneumatic tire according to claim 1, wherein the buttress grooves are arranged radially inward of a pair of first grooves, extend inclined with respect to the tire radial direction such that their radially outward ends approach each other as they move radially outward, and further comprises a pair of second grooves arranged on both sides of the imaginary line along the tire radial direction.

3. The pneumatic tire according to claim 2, wherein the buttress groove further has a connecting groove that connects the radially inner ends of a pair of first grooves and the radially outer ends of a pair of second grooves.

4. The pneumatic tire according to claim 3, wherein, in the tire axial cross section, the groove bottom of the connecting groove and the belt end, which is the outer end of the belt in the tire axial direction, are spaced 8 mm or more apart.

5. The pneumatic tire according to claim 3, wherein, in a cross-section of the tire in the axial direction, the bottom of the connecting groove has a circular arc shape that is convex outward in the tire axial direction, and the bottom of the groove is located on a circular arc with a radius of 8 mm centered on the end of the belt, or located outward in the tire axial direction from the circular arc.

6. The pneumatic tire according to claim 3, wherein at least one of the first groove and the second groove has a groove depth that gradually increases toward the connecting groove.

7. The pneumatic tire according to claim 3, wherein the groove width of the first groove, the second groove, and the connecting groove on the tire surface is 3 mm or more and 8 mm or less.

8. The pneumatic tire according to claim 7, wherein the groove width at the bottom of the first groove, the second groove, and the connecting groove is smaller than the groove width on the tire surface and is between 1 mm and 5 mm.

9. In the axial cross-section of the tire, The first angle formed by the line passing through the belt end, which is the outer end of the belt in the tire axial direction, and the line connecting the outer end of the first groove in the tire radial direction and the belt end, is 20° or more and 40° or less. The pneumatic tire according to claim 2, wherein the second angle formed by the axial line of the tire passing through the end of the belt and the line connecting the inner end of the second groove in the radial direction of the tire and the end of the belt is 20° or more and 40° or less.

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