tire

Abstract

The present invention provides a tire having improved wet road handling stability. The tire (1) has a tread portion (2) having a specified rotation direction (F). The block (5) of the tread portion (2) includes a step-in side corner portion (10) formed between a block tread (6) and a block side wall surface (7) located on the first ground contact side in the rotation direction (F). The step-in side corner portion (10) includes a first portion (11) and a second portion (12) in the tire axial direction. The first portion (11) is formed to be sharper than the second portion (12). In the transverse groove (4), the groove width (A) at the first portion (11) is greater than the groove width (B) at the second portion.

Description

Technical Field

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

[0002] Patent Document 1 below describes a pneumatic tire having blocks in a tread portion. The block edges of the blocks are chamfered. The pneumatic tire is expected to have an effect of making the ground contact pressure of the blocks uniform.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2002-36824 Summary of the invention

[0004] However, Patent Document 1 does not study the steering stability performance on a wet road surface (hereinafter, sometimes simply referred to as “wet steering stability performance”).

[0005] The present invention is proposed in view of the above actual situation, and its main purpose is to provide a tire with improved wet road handling stability.

[0006] The present invention is a tire having a tread portion with a designated rotational direction, the tread portion including at least one block row, the at least one block row being formed by a plurality of blocks arranged in the tire circumferential direction, the plurality of blocks respectively including a stepping-in side corner portion, the stepping-in side corner portion being formed between a block tread and a block side wall surface located on the first ground contacting side in the rotational direction, a transverse groove being formed between the blocks, the stepping-in side corner portion including a first portion and a second portion in the tire axial direction, the first portion being formed to be sharper than the second portion, and an angle θ1 of the first portion relative to the tire circumferential direction is larger than an angle θ2 of the second portion relative to the tire circumferential direction when the block is viewed from above, and in the transverse groove, a groove width A at the first portion is larger than a groove width B at the second portion.

[0007] In the tire of the present invention, preferably, the second portion is chamfered, and the first portion is not chamfered.

[0008] In the tire of the present invention, preferably, the second portion is formed by a chamfer, and the first portion is formed by a chamfer smaller than that of the second portion.

[0009] In the tire of the present invention, it is preferable that an angle θ1 of the first portion with respect to the tire circumferential direction is 45 degrees or more.

[0010] In the tire of the present invention, it is preferable that an angle θ1 of the first portion with respect to the tire circumferential direction is 70 degrees or more.

[0011] In the tire of the present invention, preferably, a ratio (B / A) of a groove width A at the first portion to a groove width B at the second portion is 0.50 to 0.95.

[0012] In the tire of the present invention, preferably, the second portion is chamfered, and a length of the chamfer in the tire circumferential direction, ie, a chamfer width, is 1.0 mm to 10.0 mm.

[0013] In the tire of the present invention, preferably, the second portion is chamfered, and a height of the chamfer in the tire radial direction, that is, a chamfer height, is preferably not more than 0.25 times a length of the chamfer in the tire circumferential direction.

[0014] In the tire of the present invention, preferably, the second portion is formed with a chamfer, and the chamfer is formed of a curved surface that is convex toward the outer side in the tire radial direction.

[0015] In the tire of the present invention, preferably, the second portion is chamfered, and the chamfer is formed by a flat surface.

[0016] In the tire of the present invention, preferably, the block tread has a connection portion connected to the first portion, and the connection portion is inclined toward the first portion toward the outer side in the tire radial direction.

[0017] In the tire of the present invention, preferably, each of the plurality of blocks is a shoulder block adjacent to a tread end, and the first portion is arranged closer to the tread end than the second portion.

[0018] In the tire of the present invention, preferably, each of the plurality of blocks includes a trailing-side corner portion formed between the block tread surface and a block side wall surface located on a rear ground contact side in the rotational direction, and the trailing-side corner portion is chamfered.

[0019] In the tire of the present invention, preferably, the tread portion has a main groove extending in the tire circumferential direction, and the second portion is connected to the main groove.

[0020] In the tire of the present invention, preferably, each of the plurality of blocks includes a main groove side corner portion formed between the block tread surface and a block longitudinal wall surface formed by the main groove, and the main groove side corner portion is chamfered.

[0021] In the tire of the present invention, preferably, a belt layer is provided in the tread portion, and the belt layer includes: an inner belt ply whose belt cords are inclined toward one side relative to the tire axial direction; and an outer belt ply, which is arranged on the outer side of the inner belt ply in the tire radial direction, and the belt cords of the outer belt ply are inclined in a direction opposite to the belt cords of the inner belt ply, and the belt layer is arranged in the inner area of ​​the first portion in the tire radial direction.

[0022] The tire of the present invention can improve wet steering stability by adopting the above-mentioned structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a partial plan view of the tread portion of the present embodiment.

[0024] Figure 2 It is a partial stereogram of the block.

[0025] Figure 3 yes Figure 1 CC line section view.

[0026] Figure 4 It is a partial top view of the tread portion.

[0027] Figure 5 It is a partial cross-sectional view of the tread portion.

[0028] Figure 6 It is a cross-sectional view of a block according to another embodiment.

[0029] Figure 7 is a cross-sectional view of a block according to still another embodiment.

[0030] Figure 8 It is a perspective view of a block according to still another embodiment.

[0031] Fig. 9 It is a perspective view of a block according to still another embodiment.

[0032] Fig.10 It is a perspective view of a block according to still another embodiment.

[0033] Description of symbols

[0034] 1: tire; 2: tread portion; 4: transverse groove; 5: block; 6: block tread; 7: block sidewall surface; 10: corner; 11: first part; 12: second part. DETAILED DESCRIPTION

[0035] Hereinafter, one embodiment of the present invention will be described based on the drawings.

[0036] Figure 1 2 is a partial top view of the tread portion 2 of the tire 1 of the present embodiment. In the present embodiment, the tire 1 is a pneumatic tire for a passenger car, and in particular, a high-performance tire that can be driven on roads and suitable for driving on circuits. In addition, the present invention can also be applied to pneumatic tires for motorcycles, heavy loads, and other types of tires, for example.

[0037] like Figure 1 As shown, the tire 1 has a directional pattern that specifies the rotation direction F. The rotation direction F is indicated by characters or symbols, for example, on a sidewall portion (not shown).

[0038] The tread portion 2 includes at least one block row 5R, which is formed by arranging a plurality of blocks 5 in the tire circumferential direction. The block row 5R includes transverse grooves 4 formed between the blocks 5.

[0039] Each block 5 is formed with: a block tread 6; a block side wall surface (sometimes referred to as the "first block side wall surface" in this specification) 7, which is located on the first landing side in the rotation direction F; and a stepping side corner portion 10, which is formed between the block tread 6 and the first block side wall surface 7.

[0040] The block tread 6 is a ground contact surface of the block 5 when a standard load is applied to the tire 1 in a standard state and the tire 1 contacts the flat surface at a camber angle of 0 degrees.

[0041] The "standard state" is a state where the tire 1 is assembled on a standard rim and filled with a standard internal pressure and is unloaded. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the standard state.

[0042] The “standard rim” is a rim whose specifications are prescribed for each tire in a specification system including the specifications based on the tire 1, for example, “standard rim” in JATMA, “design rim” in TRA, and “measuring rim” in ETRTO.

[0043] “Standard internal pressure” is the air pressure specified for each tire specification in the standard system including the specification on which tire 1 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 VARIOUSCOLD INFLATION PRESSURES”. If it is ETRTO, it is “INFLATION PRESSURE”.

[0044] The “standard load” is the load specified for each tire specification in the specification system including the specification on which the tire 1 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 ATVARIOUS COLD INFLATION PRESSURES”. If it is ETRTO, it is “LOADCAPACITY”.

[0045] Figure 2 This is a three-dimensional view of block 5 viewed from the side wall of the first block. Figure 2As shown, the stepping-in side corner portion 10 includes a first portion 11 and a second portion 12 in the axial direction of the tire. The first portion 11 is formed to be sharper than the second portion 12. Such a first portion 11 relatively increases the ground contact pressure of the block tread 6 on the stepping-in side corner portion 10 side, prevents the block 5 from exceeding the water film on the wet road surface, and thus improves the hydroplaning performance. In addition, the second portion 12 suppresses the increase in the ground contact pressure of the block tread 6 on the stepping-in side corner portion 10, and maintains the uniformity of the ground contact pressure. As a result, the tire 1 of this embodiment has excellent wet road handling stability performance. The "sharper" means that the angle γ between the normal line n through the block tread 6 and the imaginary line m extending outward from the block side wall surface 7 connected to the block tread 6 to the radial direction of the tire, the other side is smaller than the other side. In addition, the angle γ is preferably sharper than 15 degrees, more preferably sharper than 10 degrees, and further preferably sharper than 5 degrees. In other words, if the angle γ exceeds 15 degrees, it is preferably not sharp, if it exceeds 10 degrees, it is more preferably not sharp, and if it exceeds 5 degrees, it is even more preferably not sharp. In addition, when the chamfer 15 described later is formed on the stepping-in side corner 10 side, the minimum angle γ ( Figure 3 as shown) to judge whether it is sharp.

[0046] like Figure 1 As shown, the angle θ1 of the first portion 11 relative to the tire circumferential direction is formed to be greater than the angle θ2 of the second portion 12 relative to the tire circumferential direction. Such a first portion 11 further suppresses the block 5 from exceeding the water film. In addition, the second portion 12 can smoothly discharge the water film to the rear ground side (tread end Te side) of the rotation direction F of the transverse groove 4 by utilizing the rotation of the tire 1.

[0047] In the transverse groove 4, the groove width A at the first part 11 is formed to be larger than the groove width B at the second part 12. As a result, the water film that is suppressed by the first part 11 from crossing the block 5 can be fully discharged into the transverse groove 4. In addition, in the transverse groove 4, the flow rate when draining water at the first part 11 becomes smaller than that of the second part 12 where the angle θ2 is relatively small. Therefore, by relatively increasing the groove width A, the water film that exceeds the suppression can be discharged more smoothly. In this specification, each groove width A, B is a length orthogonal to the groove center line 4c, and is an average groove width relative to the groove length. In addition, each groove width A, B adopts the groove width when there is no chamfer in the area where the chamfer is formed described later.

[0048] In the present embodiment, the block 5 is divided by the tread end Te, the main groove 3 extending in the circumferential direction of the tire, and the transverse groove 4. In this way, the block 5 of the present embodiment is formed as a shoulder block 5S adjacent to the tread end Te. In addition, the block 5 is not limited to the shoulder block 5S, and can also be formed as an intermediate block or a crown block (not shown) arranged on the side of the tire equator C than the shoulder block 5S. The tread end Te is the end that touches the ground on the outermost side of the tire axial direction when a standard load is applied to the tire 1 in a standard state and the tire touches the flat surface at a camber angle of 0 degrees.

[0049] The main groove 3 of this embodiment extends in a lightning shape, for example, along the tire circumferential direction. In this embodiment, the main groove 3 includes: a first inclined groove portion 3A, which is inclined to one side relative to the tire axial direction; and a second inclined groove portion 3B, which is inclined in the same direction as the first inclined groove portion 3A and is inclined relative to the tire axial direction at an angle α1 smaller than that of the first inclined groove portion 3A. In addition, the main groove 3 is not limited to this form.

[0050] The first inclined groove portion 3A and the second inclined groove portion 3B are inclined, for example, toward the tread end Te side toward the rear ground contact side in the rotation direction F. In this embodiment, the first inclined groove portion 3A and the second inclined groove portion 3B are alternately arranged in the tire circumferential direction. The second inclined groove portion 3B is, for example, smoothly connected to the transverse groove 4 to form a single groove.

[0051] The transverse groove 4 of this embodiment extends in the tire axial direction and is arranged in a plurality in the tire circumferential direction. The transverse groove 4 connects the main groove 3 and the tread end Te, for example. In this embodiment, the transverse groove 4 is inclined toward the tread end Te side toward the rear ground contact side in the rotation direction F. Such transverse grooves 4 utilize the tire rotation to smoothly discharge water in the main groove 3 to the outside of the tread end Te.

[0052] For example, the angle α2 of the transverse groove 4 with respect to the tire axial direction continuously decreases toward the tread end Te side. Such transverse grooves 4 further improve wet steering stability. In addition, the transverse grooves 4 are not limited to such a form.

[0053] In this embodiment, the groove wall 4e of the transverse groove 4 is formed with a first block side wall surface 7 and a second block side wall surface 20 (described later). Figure 4 shown).

[0054] The second portion 12 of the present embodiment is formed with a chamfer 15. Such a chamfer 15 helps to improve the uniformity of the ground contact pressure of the block 5. The chamfer 15 is an inclined surface that is cut obliquely from the block tread 6 toward the side of the transverse groove 4 or the main groove 3, and is a surface that contacts the ground when the standard load is applied and the camber angle is 0 degrees. In addition, the chamfer in this specification does not include the curvature radius r ( Figure 3 In addition, the first portion 11 of the present embodiment is not chamfered.

[0055] Figure 3 yes Figure 1 The CC line section view. Figure 3 As shown, the chamfer 15 is formed by, for example, a curved surface 16 that protrudes radially outward from the tire. Such a chamfer 15 can make the ground contact pressure within the chamfer 15 more uniform. In the present embodiment, the chamfer 15 is formed so that the radius of curvature r becomes smaller toward the first block sidewall surface 7. Thus, the ground contact pressure on the side of the first block sidewall surface 7 that has a greater ground contact pressure can be reduced, the uniformity of the ground contact pressure can be improved, and the wet road handling stability performance can be improved. The radius of curvature r of the chamfer 15, for example, continuously decreases toward the first block sidewall surface 7. In addition, the chamfer 15 can also be formed by, for example, a single arc with a radius of curvature r.

[0056] If the length of the chamfer 15 in the tire circumferential direction, i.e., the chamfer width Lb, is 1.0 mm or more, it is effective for the uniformity of the ground contact pressure. If the chamfer width Lb is 10.0 mm or less, it is effective for maintaining the rigidity of the block 5 at a high level. In order to effectively exert such an effect, the chamfer width Lb is more preferably 2.0 mm or more, further preferably 3.0 mm or more, further preferably 9.0 mm or less, and more preferably 8.0 mm or less.

[0057] In order to maintain the rigidity of the block 5 in the tire circumferential direction at a high level and improve the uniformity of the ground contact pressure, the chamfer width Lb of the block 5 is preferably 10% or more, and more preferably 15% or more, of the length La of the block 5 in the tire circumferential direction (the maximum length on the tire circumferential line). In addition, the chamfer width Lb of the block 5 is preferably 25% or less, and more preferably 20% or less, of the length La of the block 5.

[0058] If the height of the chamfer 15 in the tire radial direction, i.e., the chamfer height Hb, is less than 0.25 times the chamfer width Lb, the chamfer 15 can be effectively grounded, thereby improving the uniformity of the ground contact pressure and improving the wet road handling stability. If the chamfer height Hb is more than 0.08 times the chamfer width Lb, the ground contact pressure of the chamfer 15 can be reduced, thereby improving the uniformity. In order to more effectively exert such an effect, the chamfer height Hb is more preferably less than 0.22 times the chamfer width Lb, and more preferably more than 0.10 times.

[0059] like Figure 1 As shown, the first portion 11 is arranged closer to the tread end Te than the second portion 12. Thus, the water film that is blocked from entering the block tread 6 by the first portion 11 is smoothly discharged from the tread end Te through the lateral groove 4.

[0060] Figure 4 2 is a partial top view of the tread portion 2. Figure 4As shown, the first portion 11 and the second portion 12 of the block 5 are connected in a smooth curve without a curved portion. Such first portion 11 and second portion 12 reduce the rigidity difference of the block 5, thereby improving the wet road steering stability.

[0061] In order to effectively exert the above effect, the angle θ1 of the first portion 11 is preferably greater than 45 degrees, and more preferably greater than 70 degrees. In addition, the angle θ2 of the second portion 12 is preferably less than 45 degrees, and more preferably less than 70 degrees. More specifically, the angle θ1 of the first portion 11 is preferably formed on the axially outer side of the tire from a position of 45 degrees, and the angle θ1 is more preferably formed on the axially outer side of the tire from a position of 70 degrees. In the present embodiment, the angle θ1 of the first portion 11 is formed on the axially outer side of the tire from a position of 80 degrees.

[0062] The first portion 11 of the present embodiment includes: an inner portion 11a connected to the second portion 12; and an outer portion 11b whose axial length is smaller than that of the inner portion 11a, and which connects the inner portion 11a and the tread end Te, and whose angle θ1 is smaller than that of the inner portion 11a. The outer portion 11b has, for example, an angle smaller than the angle θ2 of the second portion 12. In the present embodiment, the outer portion 11b is formed to be sharper than the second portion 12, and is not chamfered.

[0063] When the groove width B at the second portion 12 is too small, the hydroplaning performance may be deteriorated. When the groove width A at the first portion 11 is too large, the rigidity in the tire circumferential direction at the first portion 11 of the block 5 becomes small, and the wet handling stability performance may be deteriorated. Therefore, the ratio (B / A) of the groove width A at the first portion 11 to the groove width B at the second portion 12 is preferably 0.50 or more, more preferably 0.70 or more. In addition, the ratio (B / A) is preferably 0.95 or less, more preferably 0.90 or less.

[0064] In addition, when the difference Δγ between the angle γ of the first portion 11 and the angle γ of the second portion 12 is between 5 and 10 degrees, the ratio (B / A) is between 0.50 and 0.95. When the difference Δγ is less than 5 degrees or exceeds 10 degrees, the discharge of the water film cannot be well balanced at the first portion 11 and the second portion 12, and the improvement of wet handling stability performance may be reduced.

[0065] When the chamfer width Lb of the second portion 12 is 1.0 mm to 10.0 mm, the ratio (B / A) is preferably 0.50 to 0.95. When the chamfer width Lb is less than 1.0 mm or exceeds 10.0 mm, the second portion 12 cannot effectively remove the water film, and wet steering stability may not be improved.

[0066] The ratio (B / A) is preferably the groove width ratio of the lateral grooves 4 formed between the shoulder blocks. This allows the water film in the lateral grooves 4 to be smoothly discharged from the tread ends Te, so that wet steering stability performance can be effectively exhibited.

[0067] Although not particularly limited, it is preferred that the length L1 of the first portion 11 in the tire axial direction is equal to the length L2 of the second portion 12 in the tire axial direction. This has the effect of improving the wet road handling stability while improving the uniformity of the ground contact pressure. In order to effectively exert such an effect, the ratio (L1 / L2) of the length L1 of the first portion 11 to the length L2 of the second portion 12 is preferably greater than 0.3, more preferably greater than 0.4. In addition, the ratio (L1 / L2) is preferably less than 0.7, more preferably less than 0.6.

[0068] like Figure 2 As shown, the chamfer 15 of the block 5 of this embodiment includes: chamfer width Lb ( Figure 3 The present invention also provides a non-variable portion 17 that is the same as the transverse groove 4 (as shown in the figure); and a variable portion 18 with a chamfer width Lb that decreases toward the first portion 11. Such a variable portion 18 reduces the rigidity difference of the stepping-in side corner portion 10 of the block 5, thereby maintaining the wet road handling stability performance at a high level. In this embodiment, the chamfer height Hb of the variable portion 18 decreases toward the first portion 11.

[0069] like Figure 4 As shown, in this embodiment, the block side wall surface (sometimes referred to as "second block side wall surface" in this specification) 20 of the block 5 located on the rear ground contact side in the rotation direction F includes a block longitudinal wall surface 21 formed by the main groove 3. Thus, the block 5 includes: a step-out side corner portion 22 formed between the block tread 6 and the second block side wall surface 20; and a main groove side corner portion 23 formed between the block tread 6 and the block longitudinal wall surface 21.

[0070] A chamfer 24 is formed on the push-out side corner 22 of the present embodiment. The push-out side corner 22 is formed with the chamfer 24, for example, in the entire length direction thereof. In addition, a chamfer 25 is formed on the main groove side corner 23 of the present embodiment. The main groove side corner 23 is formed with the chamfer 25, for example, in the entire length direction thereof. Thus, the uniformity of the ground contact pressure of the block 5 is improved. In the present embodiment, the chamfers 24 and 25 mainly adopt the same shape as the chamfer 15. Therefore, with respect to the chamfers 24 and 25, only the parts that are different from the chamfer 15 are described. In addition, the chamfers 24 and 25 are not limited to such a method, and may also be shapes different from the chamfer 15.

[0071] The axial length of the chamfer 25, i.e., the chamfer width Le, is preferably 12.5% ​​or less, and more preferably 10.0% or less, of the axial length (maximum length) Ld of the block 5. The chamfer width Le of the chamfer 25 is preferably 2.5% or more, and more preferably 5.0% or more, of the axial length Ld of the block 5.

[0072] The block tread 6 of the block 5 of this embodiment is provided with a sipe 26 extending in the axial direction of the tire. For example, one sipe 26 is provided in each block 5. Such a sipe 26 exerts a gripping effect on a wet road surface and improves the wet road handling stability. In this specification, the sipe 26 is defined as a groove-shaped body with a sipe width of less than 1.0 mm, and is distinguished from a groove with a groove width of more than 1.0 mm.

[0073] The sipes 26 extend from the tread end Te, for example, and terminate in the block 5. In addition, in the present embodiment, the sipes 26 are inclined toward the tread end Te side toward the rear ground contact side in the rotation direction F. Such sipes 26 can suppress the reduction in the rigidity of the block 5 and can smoothly discharge the water film between the block tread 6 and the road surface to the outside of the tread end Te.

[0074] Figure 5 2 is a partial cross-sectional view of the tread portion 2. Figure 5 As shown in FIG. 1 , a belt layer 8 extending in the tire axial direction is provided in the tread portion 2, for example. The belt layer 8 of the present embodiment includes: an inner belt ply 8a, which makes the belt cords (not shown) tilted to one side relative to the tire axial direction; and an outer belt ply 8b, which makes the belt cords tilted in the opposite direction to the belt cords of the inner belt ply 8a. The belt layer 8 of the present embodiment is formed of a known material.

[0075] The belt layer 8 is, for example, arranged in the inner region R of the first portion 11 in the tire radial direction. This improves the rigidity of the block 5, increases the ground contact pressure of the first portion 11, and further suppresses the block 5 from exceeding the water film. In this embodiment, the belt layer 8 is arranged in the entire inner region R of the first portion 11.

[0076] Figure 6 is a cross-sectional view of block 5 of another embodiment (equivalent to Figure 1 The same reference numerals are given to the same components as those of the block 5 of the present embodiment, and their detailed description is omitted. Figure 6 As shown, the chamfer 15 of this embodiment is formed by, for example, a plane 27. Alternatively, the chamfer 15 may be formed by a plane 27 connected to the block tread 6 and a curved surface 16 connecting the plane 27 and the first block side wall surface 7 (not shown).

[0077] Figure 7 is a cross-sectional view of a block 5 of another embodiment (equivalent to Figure 2DD line cross-sectional view). For block 5 and Figure 6 The same components as those of the block 5 are given the same reference numerals and their detailed descriptions are omitted. Figure 7 As shown, in this embodiment, the block tread surface 6 is provided with a connecting portion 29 connected to the first portion 11 of the first block side wall surface 7 .

[0078] The connection portion 29 is inclined, for example, toward the outer side in the tire radial direction toward the first portion 11. Such a connection portion 29 increases the block height of the first portion 11, further increases the ground contact pressure of the portion, and thus further improves the hydroplaning performance.

[0079] In order to improve the above effects in a balanced manner, the height Hc of the connection portion 29 is preferably 0.25 times or less, and more preferably 0.22 times or less, of the length Lc of the connection portion 29 in the tire circumferential direction. The height Hc of the connection portion 29 is preferably 0.05 times or more, and more preferably 0.08 times or more, of the length Lc of the connection portion 29.

[0080] Although not particularly limited, the length Lc of the connection portion 29 is preferably 1.0 mm or more, more preferably 0.2 mm or more, and further preferably 0.3 mm or more. In addition, the length Lc of the connection portion 29 is preferably 10.0 mm or less, more preferably 9.0 mm or less, and further preferably 8.0 mm or less.

[0081] Figure 8 7 is a perspective view of the block 5 in another embodiment as viewed from the first block side wall surface 7. Figure 6 , 7 The same components as those of the block 5 are given the same reference numerals, and their detailed descriptions are omitted. Figure 8 As shown, the first portion 11 of the block 5 of this embodiment is formed with a smaller chamfer 30 than the second portion 12. Such a block 5 can further improve the uniformity of the grounding pressure. The chamfer 30 of the first portion 11 of this embodiment is formed, for example, with the same chamfer width Lb and the same chamfer height Hb in the entire length direction thereof.

[0082] Fig. 9 7 is a perspective view of the block 5 in another embodiment as viewed from the first block side wall surface 7. Figures 6 to 8 The same components as those of the block 5 are given the same reference numerals and their detailed descriptions are omitted. Fig. 9 As shown, in the stepping side corner portion 10 of the block 5 of this embodiment, the chamfer 15 of the second portion 12 is connected to the first portion 11 through a step surface 31 extending in the tire radial direction. In such a stepping side corner portion 10, the ground contact pressure becomes relatively high near the step surface 31, thereby further suppressing the block 5 from exceeding the water film.

[0083] Fig.10 7 is a perspective view of the block 5 in another embodiment as viewed from the first block side wall surface 7. Figures 6 to 9 The same components as those of the block 5 are given the same reference numerals and their detailed descriptions are omitted. Fig.10 As shown, the chamfer 15 of the second portion 12 of the block 5 of this embodiment is formed by the change portion 18 without forming the non-change portion 17 .

[0084] As mentioned above, although the particularly preferred embodiment of the present invention has been described in detail, the present invention is not limited to the illustrated embodiment, and can be implemented in various modified forms.

[0085] [Example]

[0086] Pneumatic tires for passenger cars were manufactured and the running performance of each test tire on a wet road was tested. Figure 1 and Figure 2 The tread portion is a block of a basic shape, and the shapes other than the blocks are the same. The test method and general specifications of the tire are as follows.

[0087] Tire size: 235 / 40R18

[0088] Rim size: 18×12J

[0089] Internal pressure: 200kPa (all wheels)

[0090] <Lap time and handling stability>

[0091] The test driver drives the test vehicle equipped with the test tire on a loop test route on an asphalt road surface with a water depth of 5 mm. Then, the lap time (driving time) when the test tire used as a benchmark is installed (benchmark example) is calculated, that is, the difference (T-Tn) between the benchmark time T and the lap time Tn when the tires of each comparative example and embodiment are installed. The lap time result is expressed as an index with the difference Δt between the lap time of comparative example 1 and the benchmark example being 100. In addition, the handling stability performance is evaluated by the test driver through the senses in consideration of the lap time. The handling stability performance result is expressed as a score with the benchmark example tire as 100. For all test results, the larger the value, the better.

[0092] Test vehicle: Passenger car capable of running in the GT3 group (racing)

[0093] "A" in Table 1 indicates that the first part (sharp corner) without chamfering is formed at the corner closest to 90 degrees relative to the tire circumferential direction and its adjacent corner. "B" indicates that all the corners on the stepping side are formed by chamfering. "C" indicates that no chamfer is formed at the stepping side corners (all are sharp). "D" indicates that the stepping side corner includes a first part without chamfering and a second part with chamfering. "E" indicates that the second part is sharper than the first part.

[0094] The “angle of the first portion” means that the first portion is formed on the outer side in the tire axial direction than the angle (angle with respect to the tire circumferential direction) described in each embodiment.

[0095] In Table 3, the examples are in a state where the chamfers are smoothly connected to the block treads, and the comparative examples are in a state where the chamfers are not smoothly connected to the block treads.

[0096] The groove width B is the same in both the example and the comparative example.

[0097] The test results are shown in Tables 1 to 4.

[0098]

Table 1

[0099]

[0100]

Table 2

[0101]

[0102]

Table 3

[0103]

[0104]

Table 4

[0105]

[0106]

Table 5

[0107]

[0108] The test results confirmed that the tires of the examples had excellent wet steering stability performance.

Claims

1. A tire having a tread portion with a designated rotation direction, wherein: The tread portion includes at least one block row, wherein the at least one block row is formed by arranging a plurality of blocks in the circumferential direction of the tire. Each of the plurality of blocks includes a stepping-in side corner portion, wherein the stepping-in side corner portion is formed between a block step surface and a block side wall surface located on a side that first touches the ground in the rotation direction. Transverse grooves are formed between the blocks. The stepping-in side corner portion includes a first portion and a second portion in the tire axial direction. The first portion is formed to be sharper than the second portion, In a plan view of the block, an angle θ1 of the first portion relative to the tire circumferential direction is larger than an angle θ2 of the second portion relative to the tire circumferential direction. In the transverse groove, the groove width A at the first portion is greater than the groove width B at the second portion, The transverse grooves extend between the blocks along the tire axial direction. The block tread has a connecting portion, which is connected to the first portion between the block tread and the transverse groove. The connecting portion is inclined toward the first portion toward the outer side in the tire radial direction.

2. The tire according to claim 1, wherein: The second portion is formed with a chamfer, and the first portion is not formed with a chamfer.

3. The tire according to claim 1, wherein: The second portion is formed by a chamfer, and the first portion is formed by a chamfer smaller than that of the second portion.

4. The tire according to any one of claims 1 to 3, wherein An angle θ1 of the first portion with respect to the tire circumferential direction is greater than or equal to 45 degrees.

5. The tire according to claim 4, wherein: An angle θ1 of the first portion with respect to the tire circumferential direction is greater than or equal to 70 degrees.

6. The tire according to any one of claims 1 to 3, wherein: A ratio (B / A) of a groove width A at the first portion to a groove width B at the second portion is 0.50 to 0.

95.

7. The tire according to any one of claims 1 to 3, wherein The second portion is formed with a chamfer, The length of the chamfer in the tire circumferential direction, ie, the chamfer width, is 1.0 mm to 10.0 mm.

8. The tire according to any one of claims 1 to 3, wherein The second portion is formed with a chamfer, The chamfer is formed by a curved surface that is convex toward the outer side in the tire radial direction.

9. The tire according to any one of claims 1 to 3, wherein The second portion is formed with a chamfer, The chamfer is formed by a flat surface.

10. The tire according to any one of claims 1 to 3, wherein The plurality of blocks are shoulder blocks adjacent to the tread ends, The first portion is arranged closer to the tread end side than the second portion.

11. The tire according to any one of claims 1 to 3, wherein The plurality of blocks each include a kick-out side corner portion formed between the block tread and a block side wall surface located on the rear ground contact side in the rotation direction. The kick-out side corner portion is chamfered.

12. The tire according to any one of claims 1 to 3, wherein The tread portion has a main groove extending in the tire circumferential direction. The second portion is connected to the main groove.

13. The tire according to claim 12, wherein: Each of the plurality of blocks includes a main groove side corner portion, wherein the main groove side corner portion is formed between the block tread surface and the block longitudinal wall surface formed by the main groove, The side corners of the main groove are chamfered.

14. The tire according to any one of claims 1 to 3, wherein A belt layer is provided in the tread portion. The belt layer includes: an inner belt ply, the belt cords of the inner belt ply are inclined toward one side relative to the tire axial direction; and an outer belt ply, which is arranged on the outer side of the inner belt ply in the tire radial direction, and the belt cords of the outer belt ply are inclined in the opposite direction to the belt cords of the inner belt ply, The belt layer is disposed in an inner region of the first portion in the tire radial direction.

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