tire

Abstract

The tire of the present invention has improved stone-trapping resistance. The tire (1) has a tread portion (2). The tread portion (2) is provided with at least one longitudinal groove (3), a first transverse groove (4) extending from the longitudinal groove (3) to the first side (F1) in the tire axial direction in a manner to form a trident-shaped groove intersection portion (6) with the longitudinal groove (3), and a land portion (5) divided on the second side (F2) in the tire axial direction of the longitudinal groove (3). The land portion (5) has a corner portion (7) protruding toward the longitudinal groove (3) side at a position opposite to the groove intersection portion (6). In a cross section passing through the groove intersection portion (6), the corner portion (7) has a tread surface (9) and a first side wall surface (10). The first side wall surface (10) is inclined toward the second side (F2) at an angle (α) of 1 to 9 degrees relative to the tread normal (n) as it moves toward the radially outer side of the tire.

Description

Technical Field

[0001] The present invention relates to tires. Background Art

[0002] Patent Document 1 listed below describes a pneumatic tire having a shoulder main groove extending in the tire circumferential direction while being curved, and a lateral groove extending from the top of the curved portion of the shoulder main groove.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2018-1940

[0004] The pneumatic tire as described above has a problem that stones are easily caught at the intersection of the shoulder main groove and the lateral groove. Summary of the invention

[0005] The present invention has been made in view of the above-mentioned actual situation, and an object of the present invention is to provide a tire capable of improving the stone pinch resistance performance.

[0006] The tire of the present invention has a tread portion, on which are provided: at least one longitudinal groove extending in the circumferential direction of the tire, a plurality of first lateral grooves extending from the longitudinal groove to the first side in the axial direction of the tire so as to form a trident-shaped groove intersection portion with the longitudinal groove, and a land portion divided by the longitudinal groove on the second side in the axial direction of the tire of the longitudinal groove, wherein the land portion has a corner portion protruding toward the longitudinal groove side at a position opposite to the groove intersection portion, and in a cross section on an axial line of the tire passing through the groove intersection portion, the corner portion has a tread surface and a first sidewall surface, and the first sidewall surface is inclined toward the second side at an angle α of 1 to 12 degrees relative to the tread normal as it moves toward the radially outer side of the tire.

[0007] In the tire according to the present invention, it is preferable that the angle α is 5 to 10 degrees.

[0008] In the tire according to the present invention, it is preferable that a tie bar formed by raising a groove bottom is provided in the first lateral groove.

[0009] The tire involved in the present invention is preferably: the above-mentioned tension bar includes a second side wall surface opposite to the above-mentioned first side wall surface of the above-mentioned corner portion in the above-mentioned cross section, and the above-mentioned second side wall surface is inclined toward the above-mentioned first side at an angle β larger than the above-mentioned angle α relative to the tread normal as it moves toward the radial outer side of the tire.

[0010] In the tire according to the present invention, it is preferable that the angle β is 5 to 13 degrees.

[0011] In the tire according to the present invention, it is preferable that an inner end of the second side wall surface in the tire radial direction is located at a groove bottom of the longitudinal groove.

[0012] In the tire according to the present invention, it is preferred that the land portion is divided into a plurality of blocks by the plurality of second lateral grooves, and the blocks have a hexagonal shape when the tread is viewed from above.

[0013] In the tire according to the present invention, it is preferable that the first side is a tread end side, the second side is a tire equator side, and the block is a crown block.

[0014] In the tire according to the present invention, it is preferable that a crown tie bar formed by raising a groove bottom is provided in the second lateral groove.

[0015] In the tire according to the present invention, it is preferred that the length of the crown reinforcement bar in the tire axial direction is 45% to 55% of the maximum width of the crown block in the tire axial direction.

[0016] In the tire according to the present invention, it is preferable that the minimum width of the crown block in the tire axial direction is 60% to 70% of the maximum width of the crown block in the tire axial direction.

[0017] In the tire according to the present invention, it is preferred that the crown block be provided with sipes extending in the tire axial direction, wherein the sipes extend in a zigzag shape in the length direction and the depth direction thereof.

[0018] In the tire according to the present invention, it is preferred that at least two sipes are provided in the crown block.

[0019] In the tire according to the present invention, it is preferred that the axial length of the sipes is 35% to 55% of the maximum axial width of the crown blocks.

[0020] In the tire according to the present invention, it is preferable that the length of the crown block in the tire circumferential direction is 75% to 85% of one pitch of the crown block in the tire circumferential direction.

[0021] The tire involved in the present invention is preferably: in the above-mentioned tread portion, a plurality of shoulder blocks arranged in the tire circumferential direction are provided through the above-mentioned plurality of first lateral grooves and the above-mentioned longitudinal grooves, and the length of the above-mentioned shoulder blocks in the tire circumferential direction is 75% to 85% of one pitch of the above-mentioned shoulder blocks in the tire circumferential direction.

[0022] The present invention can improve the stone-crushing resistance performance by adopting the above structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a plan view of a tread portion according to an embodiment of the present invention that is developed and enlarged.

[0024] Figure 2 (a) is Figure 1 AA line section view, Figure 2 (b) is a stereoscopic view of the corner portion.

[0025] Figure 3 This is a top view of the tread portion after unfolding.

[0026] Figure 4 yes Figure 3 BB line cross-sectional view.

[0027] Figure 5 This is a top view of the tread portion after unfolding.

[0028] Figure 6 This is a top view of the tread portion after unfolding.

[0029] Figure 7 (a) is a perspective view of a corner portion of another embodiment, Figure 7 (b) is a perspective view of a corner portion of still another embodiment.

[0030] Description of Reference Numerals

[0031] 1…tire; 2…tread portion; 3…longitudinal groove; 4…first transverse groove; 5…land portion; 6…groove intersection portion; 7…corner portion; 9…tread surface; 10…first sidewall surface; F1…first side; F2…second side; n…tread normal line. DETAILED DESCRIPTION

[0032] Hereinafter, one embodiment of the present invention will be described based on the drawings.

[0033] Figure 1 FIG. 2 is a plan view of the tread portion 2 of the tire 1 according to the present embodiment, which is unfolded and enlarged. Figure 1 2 shows a tread portion 2 of a pneumatic tire for heavy loads such as a light truck. In addition, the present invention can also be used for pneumatic tires for passenger cars, or tires of other categories.

[0034] like Figure 1As shown, the tread portion 2 of the tire 1 is provided with: at least one longitudinal groove 3 extending in the tire circumferential direction, a plurality of first transverse grooves 4 extending from the longitudinal groove 3 to the first side F1 in the tire axial direction, and a land portion 5 divided by the longitudinal groove 3 on the second side F2 in the tire axial direction of the longitudinal groove 3. In this embodiment, the first transverse groove 4 forms a trident-shaped groove intersection portion 6 with the longitudinal groove 3. For the above-mentioned "extending in the tire circumferential direction", if the longitudinal groove 3 extends continuously in the tire circumferential direction, it includes various forms such as straight-line, zigzag, and wavy extension. In addition, if the longitudinal groove 3 is interrupted in the tire circumferential direction, it refers to a form that is inclined at less than 45 degrees relative to the tire circumferential direction. And, for the "trident-shaped groove intersection portion", in the case of providing a pair of transverse grooves extending from the longitudinal groove to both sides of the tire axial direction, it is sufficient as long as the openings of these transverse grooves at the longitudinal grooves do not overlap in the tire circumferential direction (illustration omitted). In this case, two trident-shaped groove intersection portions are formed by a pair of transverse grooves. The above-mentioned "lateral groove" refers to a groove having a length of 20% or more of the maximum width Wt in the tire axial direction of the land portion forming the lateral groove.

[0035] The land portion 5 has a corner portion 7 protruding toward the longitudinal groove 3 at a position opposite to the groove intersection portion 6. Such a corner portion 7 has an edge component in the tire axial direction, and thus improves traction on a road surface with a low friction coefficient, such as a road surface paved with iron plates (hereinafter referred to as "low μ road performance"). In addition, for example, the protruding corner portion 7 improves the steering stability performance on a snowy road, that is, the snow performance. In addition, the above-mentioned "opposite position" in this specification refers to a position that overlaps with the opening 4a of the lateral groove 4 at the longitudinal groove 3 in the tire circumferential direction.

[0036] Figure 2 (a) is Figure 1 AA line cross-sectional view. AA line is the tire axial line passing through the groove intersection 6. Figure 2 As shown in (a) of FIG. 1 , the corner portion 7 includes the tread 9 of the land portion 5 and the first side wall surface 10. The first side wall surface 10 is connected to the tread 9 in the present embodiment, and an edge 10e is formed at a position connected to the tread 9.

[0037] The first side wall surface 10 is inclined toward the second side F2 at an angle α of 1 to 12 degrees relative to the tread normal line n as it moves toward the outer side in the tire radial direction. As a result, stones and the like (including rubble and gravel) sandwiched by the groove intersection 6 are squeezed toward the first lateral groove 4 side and discharged from the groove intersection 6 by the rolling of the tire 1. Therefore, the tire 1 of this embodiment has excellent anti-stone performance.

[0038] If the angle α is small, the force for squeezing stones and the like in the groove intersection 6 toward the first lateral groove 4 may be reduced. Therefore, the angle α is preferably 5 degrees or more. If the angle α is large, stones and the like may be caught in the first side wall surface 10. Therefore, the angle α is preferably 10 degrees or less.

[0039] like Figure 1 As shown, the first side wall surface 10 in this embodiment includes a pair of axial portions 12 connected to the longitudinal groove 3 and extending in the tire axial direction, and a circumferential portion 13 connecting the end 12e of the axial portion 12. In this embodiment, the axial portion 12 and the circumferential portion 13 extend to the groove bottom 3s of the longitudinal groove 3. Such a first side wall surface 10 improves the stone-entrapment resistance. In addition, the first side wall surface 10 is not limited to such a form.

[0040] The length L1 of the first side wall surface 10 (circumferential portion 13) in the tire circumferential direction is formed, for example, to be smaller than the opening width W1 of the first lateral groove 4 in the tire circumferential direction at the longitudinal groove 3. Thus, the reduction in the rigidity of the land portion 5 is suppressed to maintain high low-μ road performance and wear resistance. In order to effectively play such a role, the length L1 of the first side wall surface 10 is preferably less than 85% of the opening width W1 of the first lateral groove 4, more preferably less than 80%, and further preferably less than 75%. In order to improve the stone-pinching resistance, the length L1 of the first side wall surface 10 is preferably more than 55% of the opening width W1 of the first lateral groove 4, more preferably more than 60%, and further preferably more than 65%.

[0041] In order to more effectively exert the above-mentioned effects, it is preferred that the length L2 of the axial portion 12 in the tire axial direction is smaller than the groove width Wa of the longitudinal groove 3. It is preferred that the length L2 of the axial portion 12 is 15% or more of the groove width Wa of the longitudinal groove 3, and more preferably 20% or more. In addition, it is preferred that the length L2 of the axial portion 12 is 35% or less of the groove width Wa of the longitudinal groove 3, and more preferably 30% or less.

[0042] like Figure 1 and Figure 2 As shown in (a), the first lateral groove 4 is provided with a tie bar 8 formed by raising the groove bottom 4s. Such a tie bar 8 suppresses deformation of the first lateral groove 4 caused by rolling of the tire 1, thereby suppressing stones and the like from being caught in the first lateral groove 4.

[0043] In the present embodiment, the tie bar 8 includes a second side wall surface 14 that is opposite to the first side wall surface 10 of the corner portion 7. The second side wall surface 14 is inclined toward the first side F1 toward the outer side in the tire radial direction at an angle β greater than the angle α relative to the tread normal line n. Such a second side wall surface 14 applies a force toward the outer side in the tire radial direction to stones and the like that are squeezed toward the first lateral groove 4 side through the first side wall surface 10, thereby smoothly discharging the stones and the like from the first lateral groove 4.

[0044] The angle β is preferably 5 to 13 degrees. Since the angle β is 5 degrees or more, the force to the outer side of the tire radial direction can be effectively applied to stones and the like. Since the angle β is 13 degrees or less, the volume of the tie bar 8 is large, thereby greatly suppressing the deformation of the first lateral groove 4. The angle β is more preferably 6 degrees or more, preferably 12 degrees or less.

[0045] The inner end 14e of the second side wall surface 14 in the tire radial direction is located, for example, at the groove bottom 3s of the longitudinal groove 3. Such a second side wall surface 14 also effectively acts a force toward the outer side of the tire radial direction on stones and the like, and prevents stones and the like from being caught in the first lateral groove 4. "The inner end 14e is located at the groove bottom 3s" means that the inner end 14e is arranged at a position where the groove bottom 3s intersects with the groove wall surface 3a on the first side F1 of the longitudinal groove 3. In addition, when the inner end 14e of the second side wall surface 14 in the tire radial direction is located closer to the first side F1 than the groove bottom 3s, the snow performance can be improved.

[0046] The tie rod 8 has a shallow bottom surface 15 connected to the second side wall surface 14 and forming a portion where the groove depth d1 of the first lateral groove 4 is the smallest. In addition, the tie rod 8 in this embodiment includes a third side wall surface 16 connected to the shallow bottom surface 15 and inclined toward the inner side of the tire radial direction as it moves toward the first side F1. In this embodiment, the length L3 of the shallow bottom surface 15 in the tire axial direction is formed to be larger than the length L4 of the second side wall surface 14 in the tire axial direction. In this specification, the length L3 of the shallow bottom surface 15 is referred to as the length of the tie rod 8 in the tire axial direction.

[0047] Although not particularly limited, the depth d1a of the shallow bottom surface 15 is preferably 55% or more, more preferably 60% or more of the depth (maximum depth) d1 of the first lateral groove 4. The depth d1a of the shallow bottom surface 15 is preferably 75% or less, more preferably 70% or less of the groove depth d1 of the first lateral groove 4.

[0048] Figure 2 (b) is a three-dimensional view of the corner portion 7. Figure 2 As shown in (b), the corner portion 7 in this embodiment includes a main side wall surface 11 whose angle relative to the tread normal line n is different from that of the first side wall surface 10. The angle γ of the main side wall surface 11 relative to the tread normal line n is, for example, formed to be smaller than the angle α. Preferably, the angle γ of the main side wall surface 11 relative to the tread normal line n is, for example, 0 to 8 degrees. Such a main side wall surface 11 suppresses the reduction in the volume of the land portion 5 to improve the rigidity of the land portion, thereby suppressing the occurrence of uneven wear and wear to improve the wear resistance. The main side wall surface 11 is respectively connected to each axial portion 12 of the first side wall surface 10 in this embodiment. In this embodiment, the length L1 of the first side wall surface 10 in the tire circumferential direction is formed with the same length from the tread 9 to the groove bottom 3s.

[0049] like Figure 1 As shown in the figure, the land portion 5 is divided into a plurality of blocks 19 by a plurality of second lateral grooves 18. The block 19 is hexagonal when the tread is viewed from above. Such a block 19 has excellent wear resistance because the rigidity in the axial direction of the tire and the rigidity in the circumferential direction of the tire are balanced and high. The block 19 of this embodiment is a barrel-shaped hexagonal shape with the central part in the circumferential direction of the tire protruding toward both outer sides in the axial direction of the tire.

[0050] Figure 3 : is an expanded view between the tread ends Te and Te of the tread portion 2 of the present embodiment. The above-mentioned "tread end Te" in the case of a pneumatic tire refers to the outermost contact position in the axial direction of the tire when the tire 1 is mounted on a regular rim (not shown), filled with a regular internal pressure, and in a regular state without load, loaded with a regular load and grounded on a flat surface at a camber angle of 0°. The distance between the tread ends Te and Te in the tire axial direction is the tread width TW. In this specification, unless otherwise specified, the dimensions of each part of the tire 1 are values ​​in the regular state.

[0051] "Regular rims" refer to rims whose specifications are specified for each tire in the specification system including the specifications to which the tire is based. For example, if it is JATMA, it is a "standard rim", if it is TRA, it is a "design rim", and if it is ETRTO, it is a "measuring rim".

[0052] "Normal internal pressure" refers to the air pressure specified for each tire in the specification system including the specifications on which the tire is based. If it is JATMA, it is the "maximum air pressure". If it is TRA, it is the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". If it is ETRTO, it is "INFLATION PRESSURE".

[0053] "Normal load" refers to the load specified for each tire in the specification system including the specifications to which the tire is based. If it is JATMA, it is the "maximum load capacity". If it is TRA, it is the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIATION COLD INFLATION PRESSURES". If it is ETRTO, it is "LOADCAPACITY".

[0054] like Figure 3 As shown, the longitudinal groove 3 of this embodiment includes a pair of shoulder longitudinal grooves 3A, 3A arranged on the side closest to the tread end Te, and a crown longitudinal groove 3B arranged between the pair of shoulder longitudinal grooves 3A, 3A. The shoulder longitudinal groove 3A and the crown longitudinal groove 3B extend continuously in the tire circumferential direction. In addition, the longitudinal groove 3 is not limited to such a form.

[0055] In the present embodiment, the shoulder longitudinal groove 3A includes a shoulder first portion 20 that is continuously inclined toward one side (in the drawing, descending toward the right) relative to the tire circumferential direction, and a shoulder second portion 21 that is continuously inclined toward the side opposite to the shoulder first portion 20 (in the drawing, descending toward the left). For example, the shoulder first portion 20 and the shoulder second portion 21 are alternately arranged to form the shoulder longitudinal groove 3A. For example, the first side wall surface 10 of the corner portion 7 is formed in a manner that straddles the shoulder first portion 20 and the shoulder second portion 21.

[0056] In this embodiment, the crown longitudinal groove 3B includes a crown first portion 22 continuously inclined toward one side relative to the tire circumferential direction, and a crown second portion 23 continuously inclined toward the side opposite to the crown first portion 22. For example, the crown first portion 22 and the crown second portion 23 are alternately arranged to form the crown longitudinal groove 3B.

[0057] In the present embodiment, the first lateral groove 4 connects the tread end Te with the shoulder longitudinal groove 3A. The first lateral groove 4 extends, for example, parallel to the tire axial direction. The second lateral groove 18 connects the shoulder longitudinal groove 3A with the crown longitudinal groove 3B in the present embodiment. The second lateral groove 18 is, for example, continuously inclined to one side relative to the tire circumferential direction (in the figure, descending to the right).

[0058] The tread portion 2 of the present embodiment includes a plurality of shoulder blocks 25 divided by the tread end Te, the shoulder longitudinal grooves 3A, and the first lateral grooves 4, and a plurality of crown blocks 26 divided by the shoulder longitudinal grooves 3A, the crown longitudinal grooves 3B, and the second lateral grooves 18. In the present embodiment, each crown block 26 is divided by a shoulder first portion 20, a shoulder second portion 21, a crown first portion 22, and a crown second portion 23. Each shoulder block 25 is divided by, for example, a shoulder first portion 20 and a shoulder second portion 21.

[0059] The crown blocks 26 exert a higher ground contact pressure than the shoulder blocks 25. In the present embodiment, the hexagonal blocks 19 are the crown blocks 26, and thus the wear resistance is further improved.

[0060] In the present embodiment, a trident-shaped groove intersection portion (hereinafter, the groove intersection portion is referred to as the "crown groove intersection portion") 30 is formed by the crown longitudinal groove 3B and the second transverse groove 18. In addition, the crown block 26 has a corner portion (hereinafter, the corner portion is referred to as the "crown corner portion") 31 that protrudes toward the crown longitudinal groove 3B side at a position opposite to the crown groove intersection portion 30.

[0061] In the present embodiment, the crown corner portion 31 is formed in substantially the same shape as the corner portion 7. In the present specification, the detailed description of the parts of the crown corner portion 31 substantially the same as the corner portion 7 is omitted, and the parts different from the corner portion 7 are described.

[0062] Figure 4 yes Figure 3 BB line cross-sectional view. Figure 4 As shown in FIG. 1 , the crown corner portion 31 has a tread surface 9 and a fourth sidewall surface 33. The fourth sidewall surface 33 is inclined toward the tread end Te side at an angle δ of 1 to 9 degrees relative to the tread normal line n as it moves toward the outer side in the tire radial direction. Such a crown corner portion 31 also utilizes the rolling of the tire 1 to squeeze stones and the like sandwiched in the crown groove intersection portion 30 toward the second lateral groove 18 side and discharge them from the crown groove intersection portion 30. The angle δ of the fourth sidewall surface 33 is also the same as the angle α of the first sidewall surface 10, and is more preferably 5 degrees or less.

[0063] like Figure 3 As shown, in this embodiment, the fourth side wall surface 33 is formed so as to straddle the crown first portion 22 and the crown second portion 23. This further improves the stone trapping resistance.

[0064] The second lateral groove 18 is provided with a crown bar 35 having a raised groove bottom 18s. Such a crown bar 35 also improves the stone pinch resistance. In addition, the crown bar 35 increases the rigidity of the crown block 26, thereby improving the low μ road performance and wear resistance.

[0065] like Figure 4 As shown, the crown reinforcement 35 includes a crown shallow bottom surface 36 forming the portion where the groove depth d2 of the second lateral groove 18 is the smallest, and a pair of crown sidewall surfaces 37 arranged on both sides of the length direction of the crown shallow bottom surface 36 and inclined toward the radial inside of the tire as it moves toward the longitudinal groove 3 side.

[0066] Although not particularly limited, the depth d2a of the crown shallow bottom surface 36 is preferably 55% or more, more preferably 60% or more of the depth (maximum depth) d2 of the second lateral groove 18. The depth d2a of the crown shallow bottom surface 36 is preferably 75% or less, more preferably 70% or less of the groove depth d2 of the second lateral groove 18.

[0067] It is preferred that each crown sidewall surface 37 is inclined at an angle ζ greater than the angle δ of the fourth sidewall surface 33 relative to the tread normal line n. Thus, a force is applied to the stone or the like extruded from the fourth sidewall surface 33 toward the second lateral groove 18 side in the tire radial direction outward, thereby smoothly discharging the stone or the like from the second lateral groove 18. It is more preferred that the angle ζ of the crown sidewall surface 37 is 5 to 10 degrees.

[0068] Figure 5 2 is a top view of the tread portion 2 after it is unfolded. Figure 5As shown, it is preferred that the length L5 of the crown tie bar 35 in the tire axial direction is 45% to 55% of the maximum width Wt of the crown block 26 in the tire axial direction. Since the length L5 of the crown tie bar 35 is 45% or more of the maximum width Wt of the crown block 26, the deformation of the second lateral groove 18 is greatly suppressed. Since the length L5 of the crown tie bar 35 is 55% or less of the maximum width Wt of the crown block 26, high snow performance is maintained. The length L5 of the crown tie bar 35 is the length of the crown shallow bottom surface 36 in the tire axial direction.

[0069] In this embodiment, a slit-shaped sipe 39 is formed in each of the tie bar 8 and the crown tie bar 35. Such a sipe 39 appropriately reduces the rigidity of the first lateral groove 4 and the second lateral groove 18, and deforms each lateral groove 4, 18 when each block 25, 26 touches the ground, thereby helping to discharge stones and the like caught in these lateral grooves 4, 18.

[0070] In this specification, the width of the "sipe-like portion" and the "sipe" described later is less than 1.5 mm, and is clearly distinguished from the longitudinal groove 3 and other grooves with a groove width of more than 1.5 mm. In this specification, the sipe-like portion is a groove-like body formed at the bottom of the groove, and the sipe is a groove-like body formed on the tread of the land portion.

[0071] The sipe-shaped portion (hereinafter referred to as "shoulder sipe-shaped portion") 39A provided in the tie bar 8 is not connected to the second side wall surface 14 in the present embodiment, but terminates in the shallow bottom surface 15. In addition, the shoulder sipe-shaped portion 39A is not connected to the third side wall surface 16, for example, but terminates in the shallow bottom surface 15. The shoulder sipe-shaped portion 39A is provided at the central portion of the shallow bottom surface 15 in the tire circumferential direction in the present embodiment.

[0072] The sipe-shaped portion (hereinafter referred to as "crown sipe-shaped portion") 39B provided in the crown tie bar 35 is provided in the crown shallow bottom surface 36 in the present embodiment, and extends to the crown sidewall surface 37 on both sides to form a terminal. The crown sipe-shaped portion 39B is provided, for example, at the center portion of the crown shallow bottom surface 36 in the tire circumferential direction.

[0073] The ratio (L6 / L5) of the length L6 of the crown sipe 39B in the tire axial direction to the length L5 of the crown tie bar 35 is, for example, formed to be larger than the ratio (L7 / L3) of the length L7 of the shoulder sipe 39A in the tire axial direction to the length L3 of the tie bar 8. Thus, the deformation of the second lateral groove 18 is increased, so that stones and the like sandwiched between the crown blocks 26, 26 with a relatively large ground contact pressure can be smoothly discharged.

[0074] Although not particularly limited, the ratio of the length L7 of the shoulder sipe 39A to the length L3 of the reinforcing bar 8 (L7 / L3) is preferably 0.50 or more, more preferably 0.55 or more. The above ratio (L7 / L3) is preferably 0.70 or less, more preferably 0.65 or less. The ratio of the length L6 of the crown sipe 39B to the length L5 of the crown reinforcing bar 35 (L6 / L5) is preferably 0.80 or more, more preferably 0.85 or more.

[0075] Figure 6 FIG. 2 is a top view of the tread portion 2 of the present embodiment after it is unfolded. Figure 6 As shown, the crown block 26 is provided with a sipe 40 extending in the tire axial direction. Such a sipe 40 exerts a scraping effect and improves the low μ road performance.

[0076] The sipes 40 extend in a zigzag shape in the length direction and the depth direction. Such sipes 40 can suppress the reduction of the rigidity of the crown block 26, maintain the low μ road performance, and improve the wear resistance. The sipes 40 have a three-dimensional shape called Miura fold, for example.

[0077] At least two sipes 40 are provided in the crown block 26. This enhances the above-mentioned effect. In the present embodiment, three sipes 40 are provided in each crown block 26.

[0078] The sipes 40 include first sipes 40A whose both ends terminate in the crown block 26 and second sipes 40B whose both ends are connected to the first sidewall surface 10 and the fourth sidewall surface 33. The first sipes 40A and the second sipes 40B extend in a zigzag shape in their length direction and depth direction, for example.

[0079] The axial length W2 of the sipe 40 is preferably 35% to 55% of the maximum width Wt of the crown block 26. Such sipes 40 improve low μ road performance and wear resistance in a balanced manner. The first sipe 40A of the sipe 40 of the present embodiment has the above-mentioned length.

[0080] The crown block 26 has a corner 41 facing the area where the longitudinal groove 3 and the second lateral groove 18 intersect. The corner 41 includes a first corner 41A facing the intersection area of ​​the crown longitudinal groove 3B and the second lateral groove 18, and a second corner 41B facing the intersection area of ​​the shoulder longitudinal groove 3A and the second lateral groove 18. When the tread is viewed from above, the crown block 26 of this embodiment is provided with a diamond cut portion (Diamond Cut) 42 at the corner 41 of the first corner 41A and the second corner 41B facing the same second lateral groove 18, which has a smaller inner angle θ. The diamond cut portion 42 is an inclined surface 42a that is inclined toward the inner side of the tire radial direction as it moves from the tread 9 toward the longitudinal groove 3 and the second lateral groove 18. The inclined surface 42a is triangular in shape when the tread is viewed from above. Such a diamond cut portion 42 maintains low μ road performance and improves wear resistance.

[0081] The minimum axial width Wc of the crown block 26 is preferably 60% to 70% of the maximum width Wt of the crown block 26. Such a crown block 26 prevents stones from being caught in the second lateral groove 18 and increases the edge component in the axial direction of the tire, thereby improving snow performance and low μ road performance.

[0082] The length Lc of the crown block 26 in the tire circumferential direction is preferably 75% to 85% of one pitch P1 in the tire circumferential direction of the crown block 26. Such a crown block 26 has a large rigidity in the tire circumferential direction, thereby improving low μ road performance and wear resistance.

[0083] The circumferential length Ls of the shoulder block 25 is preferably 75% to 85% of one circumferential pitch P2 of the shoulder block 25. Such a shoulder block 25 has high circumferential rigidity, thereby improving low μ road performance and wear resistance in a balanced manner.

[0084] The land ratio of the shoulder land portion 5s formed by the shoulder blocks 25 and the first lateral grooves 4 is preferably 70% to 90%. This improves the wear resistance and low μ road performance in a balanced manner.

[0085] For example, it is preferred that the groove width Wa of each longitudinal groove 3 is ( Figure 1 In the case of a heavy-duty pneumatic tire, for example, the groove depth D of each longitudinal groove 3 is preferably 2.0% to 8.0% of the tread width. Figure 4 For example, the groove width Wb of the first lateral groove 4 and the second lateral groove 18 is preferably 2.0% to 8.0% of the tread width. The groove depth d1a of the first lateral groove 4 (depth of the shallow bottom surface 15) and the groove depth d2a of the second lateral groove 18 (depth of the crown shallow bottom surface 36) are preferably 30% to 70% of the groove depth D of the longitudinal groove 3.

[0086] Figure 7(a) is a stereoscopic view of a corner portion 7 of another embodiment. The same reference numerals are used for the same structures as the corner portion 7 of this embodiment, and their detailed description is omitted. For the corner portion 7 of this embodiment, the length L1 of the first side wall surface 10 in the tire circumferential direction decreases from the tread surface 9 toward the groove bottom 3s. Such a first side wall surface 10 suppresses the reduction of the rigidity of the land portion 5 and maintains high stone-entrapment resistance.

[0087] Figure 7 (b) is a stereoscopic view of a corner portion 7 of another embodiment. The same reference numerals are used for the same structures as the corner portion 7 of this embodiment, and detailed description thereof is omitted. For the corner portion 7 of this embodiment, the first side wall surface 10 forms a terminal before reaching the groove bottom 3s. Such a corner portion 7 further suppresses the reduction in rigidity of the land portion 5 and maintains the anti-stone clamping performance.

[0088] As mentioned above, although the tire which concerns on one embodiment of this invention is demonstrated in detail, this invention is not limited to the said specific embodiment, It can be implemented by changing into various forms.

[0089] Based on the specifications in Table 1 and Table 2, a prototype with Figure 3 The basic pattern size of the pneumatic tire for light trucks is 205 / 85R16. The stone pinch resistance, wear resistance, snow performance, and low μ road performance of each test tire were tested. The common specifications and test methods of each test tire are as follows.

[0090] Installed rim: 16×5.5J

[0091] Tire internal pressure: 600kPa

[0092] Length of the first sipe (W2 / Wc): 45%

[0093] Depth of the first transverse groove (d2a / D): 50%

[0094] Length of crown reinforcement (L5 / Wt): 50%

[0095] Number of slots: 3

[0096] Longitudinal groove: Sawtooth shape

[0097] Diamond cut: Yes

[0098] Crown groove: Yes

[0099] Angle γ of the main side wall: 5 degrees

[0100] <Stone-crushing resistance and wear resistance>

[0101] Each test tire was installed on all wheels of a two-wheel drive vehicle (unloaded) with a displacement of 3000cc. The vehicle was driven by a test driver on a gravel road. After driving, the state of stone clamping and wear (eccentric wear and groove depth) was confirmed by visual observation of the test driver, and the stone clamping resistance and wear resistance were evaluated according to the sensory organs of the test driver. The results are expressed as a score of 100 for the stone clamping resistance and wear resistance of Example 1. The larger the value, the better the two properties. In Comparative Example 1, the first side wall surface (formed only by the main side wall surface) is not provided.

[0102] <Snow performance and low-μ road performance>

[0103] The test driver drove the vehicle on a snowy road and a steel plate. The test driver evaluated the handling stability and traction at this time. The results were expressed with a score of 100 for Example 1. Both performances were considered acceptable if they were 95 or above.

[0104] The test results are shown in Tables 1 and 2.

[0105]

Table 1

[0106]

[0107]

Table 2

[0108]

[0109] The test results show that the tire of the embodiment is excellent in stone pinch resistance. In addition, the tire of the embodiment maintains snow performance and low μ road performance, and is also excellent in wear resistance.

Claims

1. A tire having a tread portion, wherein: The tread portion is provided with: a pair of shoulder longitudinal grooves extending in the tire circumferential direction, a crown longitudinal groove disposed between the pair of shoulder longitudinal grooves, a plurality of first lateral grooves extending from the shoulder longitudinal grooves toward the tread end side in the tire axial direction in a manner of forming a trident-shaped groove intersection with the shoulder longitudinal grooves, and a pair of land portions divided by the pair of shoulder longitudinal grooves and the one crown longitudinal groove, The land portion has a corner portion that is convex toward the shoulder longitudinal groove side at a position opposite to the groove intersection portion. In a cross section on a tire axial line passing through the groove intersection portion, the corner portion has a tread surface and a first side wall surface. The first sidewall surface is inclined toward the tire equator at an angle α of 1 to 12 degrees relative to the tread normal line as it moves toward the tire radial direction outer side. The first transverse groove is provided with a tie rod for raising the groove bottom. The tie rod includes a second side wall surface facing the first side wall surface of the corner portion in the cross section. The second side wall surface is inclined toward the tread end side at an angle β greater than the angle α with respect to the tread normal line as it goes outward in the tire radial direction. The land portion is divided into a plurality of crown blocks by a plurality of second lateral grooves. A trident-shaped crown groove intersection portion is formed by the second transverse groove and the crown longitudinal groove, The land portion has a crown corner portion that is convex toward the crown longitudinal groove side at a position opposite to the crown groove intersection portion. The crown corner portion has a tread surface and a fourth sidewall surface, The second lateral groove is provided with a crown reinforcement bar which makes the groove bottom bulge. The crown reinforcement includes a crown sidewall surface inclined at an angle greater than an angle of the fourth sidewall surface relative to the tread normal line, The first side wall surface includes: a pair of axial portions connected to the shoulder longitudinal groove and extending in the tire axial direction; and a circumferential portion connecting the ends of the pair of axial portions. The length of the first side wall surface in the tire circumferential direction decreases from the tread surface toward the groove bottom of the shoulder longitudinal groove.

2. The tire according to claim 1, wherein: The angle α is 5 to 10 degrees.

3. The tire according to claim 1 or 2, wherein: The angle β is 5 to 13 degrees.

4. The tire according to claim 1 or 2, wherein: An inner end of the second side wall surface in the tire radial direction is located at a groove bottom of the shoulder longitudinal groove.

5. The tire according to claim 1 or 2, wherein: When the tread is viewed from above, the crown blocks are hexagonal in shape.

6. The tire according to claim 1 or 2, wherein: The length of the crown reinforcement in the tire axial direction is 45% to 55% of the maximum width of the crown block in the tire axial direction.

7. The tire according to claim 1 or 2, wherein: The minimum width of the crown block in the tire axial direction is 60% to 70% of the maximum width of the crown block in the tire axial direction.

8. The tire according to claim 1 or 2, wherein: The crown block is provided with a sipe extending in the axial direction of the tire. The sipes extend in a sawtooth shape in the length direction and the depth direction thereof.

9. The tire according to claim 8, wherein: At least two sipes are provided on the crown block.

10. The tire according to claim 8, wherein: The length of the sipe in the tire axial direction is 35% to 55% of the maximum width of the crown block in the tire axial direction.

11. The tire according to any one of claims 1, 2, 9 and 10, wherein: The length of the crown block in the tire circumferential direction is 75% to 85% of one pitch of the crown block in the tire circumferential direction.

12. The tire according to any one of claims 1, 2, 9 and 10, wherein: The tread portion includes a plurality of shoulder blocks arranged in a tire circumferential direction through the plurality of first lateral grooves and the shoulder longitudinal grooves. The length of the shoulder block in the tire circumferential direction is 75% to 85% of one pitch of the shoulder block in the tire circumferential direction.

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