tire

Abstract

To improve brake performance at the time of turning.SOLUTION: A tire 1 is given in which an outer lateral groove 8 and an inner lateral groove 9 are arranged in a tread part 2. The outer lateral groove 8 and the inner lateral groove 9 each include a first groove wall 10 at a first arrival side of a tire rotation direction R. A first chamfer part 13 is formed at least at a part of a groove edge 10e of each first groove wall 10. Regarding the cross section of the lateral groove 4, a virtual chamfer cross-section area So1 of the first chamfer part 13 of the outer lateral groove 8 is larger than a virtual chamfer cross-section area Si1 of the first chamfer part 13 of the inner lateral groove 9.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Patent Document 1 below describes a tire having a tread portion with a specified mounting direction on a vehicle. The tread portion includes an outer shoulder land portion formed with an outer shoulder transverse groove and an inner shoulder land portion formed with an inner shoulder transverse groove. The outer shoulder transverse groove has a pair of outer groove wall surfaces. The inner shoulder transverse groove has a pair of inner transverse groove wall surfaces. The pair of outer groove wall surfaces are provided with outer transverse tread side portions extending with a gentle slope to the tread surface. The pair of inner transverse groove wall surfaces are provided with inner transverse tread side portions extending with a gentle slope to the tread surface.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, a person or an object may suddenly jump out onto the traveling path of a vehicle. In such a case, in order to avoid a collision with these, the vehicle may be braked while making a large turn. Therefore, it is required that the tire improve the braking performance during turning.

[0005] The present invention has been devised in view of the above actual situation, and the main object is to provide a tire capable of improving the braking performance during turning.

Means for Solving the Problems

[0006] The present invention relates to a tire having a tread portion, wherein the tread portion has a specified orientation for mounting on a vehicle and a specified direction of tire rotation, the tread portion includes an outer tread end located on the outside of the vehicle when mounted on the vehicle, an inner tread end located on the inside of the vehicle when mounted on the vehicle, and a plurality of lateral grooves extending in the direction of the tire axis, the plurality of lateral grooves include an outer lateral groove located on the outer tread end side of the tire equator and an inner lateral groove located on the inner tread end side of the tire equator, the outer lateral groove and the inner lateral groove each include a first groove wall on the leading side in the direction of tire rotation, at least a portion of the groove edge of each first groove wall is formed with a first chamfer, and in the cross-section of the lateral groove, the virtual chamfer cross-sectional area So1 of the first chamfer of the outer lateral groove is larger than the virtual chamfer cross-sectional area Si1 of the first chamfer of the inner lateral groove. [Effects of the Invention]

[0007] By adopting the above configuration, the tire of the present invention can improve braking performance during cornering. [Brief explanation of the drawing]

[0008] [Figure 1] This is a plan view of the tread portion showing one embodiment of the tire of the present invention. [Figure 2] (A) is a cross-sectional view along line AA in Figure 1, and (B) is a cross-sectional view along line BB in Figure 1. [Figure 3] This is a cross-sectional view of the horizontal groove. [Figure 4] (A) is a cross-sectional view of the first outer transverse groove 8A, and (B) is a cross-sectional view of the second outer transverse groove 8B. [Figure 5] This is a schematic cross-sectional view showing the deformation of the lateral groove during braking. [Modes for carrying out the invention]

[0009] One embodiment of the present invention will be described below with reference to the drawings. Figure 1 is a plan view of the tread portion 2 of a tire 1 showing one embodiment of the present invention. The tire 1 of the present invention is used, for example, as a pneumatic tire for a passenger car. However, the tire 1 of the present invention may also be used, for example, as a pneumatic tire for heavy loads or for motorcycles, and as a non-pneumatic tire that is not filled with compressed air.

[0010] The tread portion 2 has a specified orientation for mounting on the vehicle. As a result, the tire 1 has an outer tread end T1 that is located on the outside of the vehicle when mounted on the vehicle, and an inner tread end T2 that is located on the inside of the vehicle. Furthermore, the tread portion 2 of the present invention has a specified tire rotation direction R.

[0011] The outer tread edge T1 and the inner tread edge T2 are, in the case of a pneumatic tire, the outermost contact points in the tire's axial direction when a normal load is applied to the tire 1 in its normal state, with a camber angle of 0°, and in contact with a flat surface. The "normal state" refers to the case of a pneumatic tire 1 for which various standards have been defined, where the tire is mounted on a normal rim, filled with the normal internal pressure, and under no load. For tires for which various standards have not been defined, or for non-pneumatic tires, the normal state refers to the standard usage state according to the tire's intended use, and is under no load. In this specification, unless otherwise specified, the dimensions of each part of the tire 1 are values ​​measured under the normal state. The axial distance between the outer tread edge T1 and the inner tread edge T2 is the tread width TW.

[0012] The aforementioned "standard rim" refers to the rim specified for each tire in the standards system, including the standard on which tire 1 is based. For example, it is the "standard rim" for JATMA, the "Design Rim" for TRA, and the "Measuring Rim" for ETRTO.

[0013] The "normal internal pressure" is the air pressure determined for each tire in the standard system including the standards on which the tire 1 is based. In the case of JATMA, it is the "maximum air pressure"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "INFLATION PRESSURE".

[0014] The "normal load" is the load determined for each tire in the standard system including the standards on which the tire 1 is based. In the case of JATMA, it is the "maximum load capacity"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "LOAD CAPACITY". In the case of a tire for which various standards are not defined, the "normal load" refers to the maximum load applicable in using the tire, in accordance with the above-mentioned standards.

[0015] In the tread portion 2 of the present embodiment, a plurality of lateral grooves 4 extending in the tire axial direction are provided. The plurality of lateral grooves 4 include an outer lateral groove 8 arranged on the outer tread end T1 side with respect to the tire equator C and an inner lateral groove 9 arranged on the inner tread end T2 side with respect to the tire equator C.

[0016] The outer lateral groove 8 and the inner lateral groove 9 each include a first groove wall 10 on the leading side in the tire rotation direction R. Further, the outer lateral groove 8 and the inner lateral groove 9 each include a second groove wall 11 on the trailing side in the tire rotation direction R. In a tread plan view, the first groove wall 10 and the second groove wall 11 each extend in the longitudinal direction of the outer lateral groove 8 and the inner lateral groove 9.

[0017] FIG. 2(A) is a cross-sectional view taken along line A-A of FIG. 1, showing the cross-section of the outer lateral groove 8. FIG. 2(B) is a cross-sectional view taken along line B-B of FIG. 1, showing the cross-section of the inner lateral groove 9. As shown in FIG. 2, at least a part of the groove edge 10e of each first groove wall 10 is formed with first chamfered portions 13A and 13B, respectively.

[0018] FIG. 5 is a cross-sectional view showing a state in which the transverse groove 4 without a chamfer portion is deformed by braking. In FIG. 5, the tire is traveling from the left side to the right side of the figure, and the traveling direction is indicated by reference sign A. As shown in FIG. 5, generally, during braking, the groove edge e of the first groove wall 10 of the transverse groove 4 is greatly deformed so as to be drawn toward the tread surface (tread tread surface) 2a side of the tread portion 2, and tends to reduce the ground contact area of the tread tread surface 2a connected to the first groove wall 10. However, in the present embodiment, during braking, the first chamfer portion 13 is deformed so as to contact the road surface, so that a decrease in the ground contact area can be suppressed. Thereby, the basic braking performance is improved.

[0019] Also, generally, when the outer tread end T1 side is the turning outside, a greater lateral force acts on the tread portion 2 on the outer tread end T1 side than on the tread portion 2 on the inner tread end T2 side when the inner tread end T2 side is the turning outside. As shown in FIG. 2, in the present invention, in the cross section of the transverse groove 4, the virtual chamfer cross-sectional area So1 of the first chamfer portion 13A of the outer transverse groove 8 is formed larger than the virtual chamfer cross-sectional area Si1 of the first chamfer portion 13B of the inner transverse groove 9. Thereby, even during braking of traveling such that the outer tread end T1 side is the turning outside, the first chamfer portion 13A is deformed so as to sufficiently contact the road surface, and a decrease in the ground contact area of the land portion to which the outer transverse groove 8 is connected is suppressed. Therefore, the tire 1 of the present invention can improve the braking performance during turning.

[0020] As shown in FIG. 1, the tread portion 2 of the present embodiment is provided with a circumferential groove 3 that continuously extends in the tire circumferential direction. In the present embodiment, the circumferential groove 3 includes a first circumferential groove 21 adjacent to the outer tread end T1, a second circumferential groove 22 located on the inner tread end T2 side with respect to the first circumferential groove 21, and a third circumferential groove 23 located on the inner tread end T2 side with respect to the second circumferential groove 22. The second circumferential groove 22 is located, for example, on the outer tread end T1 side with respect to the tire equator C. The third circumferential groove 23 is located, for example, on the inner tread end T2 side with respect to the tire equator C. Note that the circumferential groove 3 is not limited to three, and may be four or more.

[0021] The tread portion 2 is formed, for example, an outer shoulder land portion 5A, an outer crown land portion 5B, an inner shoulder land portion 5C, and an inner crown land portion 5D. The outer shoulder land portion 5A is divided, for example, between the outer tread end T1 and the first circumferential groove 21. The outer crown land portion 5B is divided, for example, between the first circumferential groove 21 and the second circumferential groove 22. The inner shoulder land portion 5C is divided, for example, between the inner tread end T2 and the third circumferential groove 23. The inner crown land portion 5D is divided, for example, between the third circumferential groove 23 and the second circumferential groove 22. The outer crown land portion 5B and the inner crown land portion 5D are formed, for example, as rib-like bodies without transverse grooves that cross the land portion. Note that each land portion 5A to 5D is not limited to the illustrated configuration.

[0022] In this embodiment, the lateral groove 4 extends in a straight line. The lateral groove 4 may also extend in a wavy, zigzag, or arc shape, for example. In this embodiment, the lateral groove 4 is inclined with respect to the tire axis. The lateral groove 4 may also extend parallel to the tire axis, for example. In this specification, the lateral groove 4 and the circumferential groove 3 are groove-like bodies with a groove width of 1.5 mm or more, and are clearly distinguished from notched sipes with a width of 1.5 mm or less. The groove width W1 of the lateral groove 4 is preferably, for example, 0.5% to 5.0% of the tread width TW. The groove depth D1 of the lateral groove 4 (shown in Figure 3) is preferably, for example, 3 to 8 mm.

[0023] In this embodiment, the outer transverse groove 8 is provided on the outer shoulder base 5A. The outer transverse groove 8 may also be provided on the outer crown base 5B, for example. In this embodiment, the outer transverse groove 8 crosses the outer shoulder base 5A. The outer transverse groove 8 may terminate at one end within the outer shoulder base 5A, or at both ends within the outer shoulder base 5A.

[0024] In this embodiment, the inner transverse groove 9 is provided in the inner shoulder land portion 5C. The inner transverse groove 9 in this embodiment traverses the inner shoulder land portion 5C. For example, one end of the inner transverse groove 9 may terminate within the inner shoulder land portion 5C, or both ends may terminate within the inner shoulder land portion 5C.

[0025] The first chamfered portion 13A of the outer transverse groove 8 is preferably provided for 70% or more of the length of the first groove wall 10A, more preferably for 80% or more, and even more preferably for 85% or more. In this embodiment, the first chamfered portion 13A of the outer transverse groove 8 is formed over the entire length of the first groove wall 10A. Similarly, the first chamfered portion 13B of the inner transverse groove 9 is preferably provided for 70% or more of the length of the first groove wall 10B, more preferably for 80% or more, and even more preferably for 85% or more. In this embodiment, the first chamfered portion 13B of the inner transverse groove 9 is formed over the entire length of the first groove wall 10B. The lengths of the chamfered portions described later are similarly defined.

[0026] As shown in Figures 2(A) and (B), at least a portion of the groove edge 11e of each second groove wall 11 has a second chamfer portion 14A, 14B formed thereon.

[0027] During braking, as described above, the contact area of ​​the first groove wall 10 becomes smaller than that of the second groove wall 11. For this reason, in the cross-section of the lateral groove 4, it is desirable to make the virtual chamfer cross-sectional area Si1 of the first chamfer portion 13B of the inner lateral groove 9 larger than the virtual chamfer cross-sectional area Si2 of the second chamfer portion 14B of the inner lateral groove 9, thereby increasing the contact area during braking. If the virtual chamfer cross-sectional area Si1 is excessively larger than the virtual chamfer cross-sectional area Si2, the surface area of ​​the tread surface 2a will become smaller, which may prevent stable driving performance (handling stability) including during cornering and straight driving. For this reason, it is desirable that the virtual chamfer cross-sectional area Si1 be 1.1 times or more of the virtual chamfer cross-sectional area Si2, more preferably 1.2 or more, even more preferably 1.3 or more, preferably 1.8 or less, even more preferably 1.7 or less, and even more preferably 1.6 or less.

[0028] During braking, the outer lateral groove 8, like the inner lateral groove 9, has a smaller contact area between the first groove wall 10 and the second groove wall. For this reason, in the cross-section of the lateral groove 4, the virtual chamfer cross-sectional area So1 of the first chamfer portion 13A of the outer lateral groove 8 is formed to be larger than the virtual chamfer cross-sectional area So2 of the second chamfer portion 14A of the outer lateral groove 8. To improve braking performance and steering stability during cornering, the virtual chamfer cross-sectional area So1 is preferably 1.1 times or more, more preferably 1.2 times or more, even more preferably 1.3 times or more, preferably 1.8 times or less, even more preferably 1.7 times or less, and even more preferably 1.6 times or less than the virtual chamfer cross-sectional area So2.

[0029] Furthermore, in order to improve braking performance during cornering, it is desirable that the ratio of virtual chamfer cross-sectional area So1 to virtual chamfer cross-sectional area So2 (So1 / So2) in the cross-section of the lateral groove 4 be greater than the ratio of virtual chamfer cross-sectional area Si1 to virtual chamfer cross-sectional area Si2 (Si1 / Si2). In order to improve braking performance and steering stability performance during cornering in a balanced manner, the ratio (So1 / So2) / (Si1 / Si2) is preferably 1.1 or greater, more preferably 1.2 or greater, even more preferably 1.3 or greater, preferably 1.8 or less, more preferably 1.7 or less, and even more preferably 1.6 or less.

[0030] Figure 3 is a cross-sectional view of the lateral groove 4. As shown in Figure 3, each first groove wall 10 further includes a first main body portion 15 that connects the first chamfered portion 13 to the groove bottom 4s of the lateral groove 4 and is inclined at a smaller angle with respect to the normal n1 of the tread surface 2a than the first chamfered portion 13. The second groove wall 11 further includes a second main body portion 16 that connects the second chamfered portion 14 to the groove bottom 4s and is inclined at a smaller angle with respect to the normal n1 of the tread surface 2a than the fourth chamfered portion 34. The cross-sectional shape of the lateral groove 4 is not limited to the illustrated embodiment.

[0031] In this specification, the virtual chamfer cross-sectional area S of each chamfered portion (including the chamfered portions described later) is the area of ​​the region enclosed by the first virtual line m1, the second virtual line m2, and each chamfered portion 13, 14. The first virtual line m1 is a line segment that smoothly extends the tread surface 2a toward the lateral groove 4. The second virtual line m2 is a line segment that smoothly extends each main body portion 15, 16 of the groove wall of the lateral groove 4 toward the radially outward direction of the tire. If the virtual chamfer cross-sectional area S changes along the length of the horizontal groove 4, the average of the maximum and minimum values ​​of the virtual chamfer cross-sectional area S is adopted.

[0032] The virtual chamfer cross-sectional area S of each chamfered section is 0.5 mm 2 It is desirable that the dimensions be as described above. This allows for an effective increase in the contact area when braking force is applied. If the virtual chamfer cross-sectional area S is excessively large, the area of ​​the tread surface 2a connected to this chamfer 13 will decrease, which may reduce the tread rigidity. For this reason, the virtual chamfer cross-sectional area S should be 0.8 mm 2 The above is more preferable, 1.1 mm 2 The above is even more desirable, 2.0 mm 2 The following is preferable, 1.7 mm 2 The following is more preferable: 1.4 mm 2 The following is even more desirable.

[0033] As shown in Figure 3, the length Ha in the tire radial direction of each chamfered portion (including the chamfered portion described later) is preferably 5% or more of the groove depth D1 of the lateral groove 4, more preferably 8% or more, even more preferably 11% or more, preferably 20% or less, more preferably 17% or less, and even more preferably 14% or less. Furthermore, the angle α1 of the first chamfered portion 13 with respect to the normal n1 and the angle α1 of the second chamfered portion 14 with respect to the normal n1 are preferably 30 degrees or more, more preferably 35 degrees or more, even more preferably 40 degrees or more, preferably 60 degrees or less, more preferably 55 degrees or less, and even more preferably 50 degrees or less. In addition, the angle α2 of the first main body portion 15 with respect to the normal n1 and the angle α2 of the second main body portion 16 with respect to the normal n1 are preferably between -15 degrees and +15 degrees.

[0034] As shown in Figure 1, in this embodiment, the outer lateral groove 8 includes a first outer lateral groove 8A having a first angle θ1 with respect to the tire axis, and a second outer lateral groove 8B having a second angle θ2 that is larger than that of the first outer lateral groove 8A with respect to the tire axis.

[0035] Figure 4(A) is a cross-sectional view of the first outer transverse groove 8A. Figure 4(B) is a cross-sectional view of the second outer transverse groove 8B. Furthermore, it is desirable that the following relationships be satisfied. Sa1 / Sa2>Sb1 / Sb2 Here, Sa1 is the virtual chamfer cross-sectional area of ​​the first chamfer portion 13e of the first outer transverse groove 8A, Sa2 is the virtual chamfer cross-sectional area of ​​the second chamfer portion 14e of the first outer transverse groove 8A, Sb1 is the virtual chamfer cross-sectional area of ​​the first chamfer portion 13i of the second outer transverse groove 8B, and Sb2 is the virtual chamfer cross-sectional area of ​​the second chamfer portion 14i of the second outer transverse groove 8B. The first outer lateral groove 8A experiences a greater braking force and greater deformation of the groove edge compared to the second outer lateral groove 8B, resulting in a smaller contact area. Therefore, by satisfying the above relationship, the contact area of ​​the first chamfered portion 13e of the first outer lateral groove 8A can be increased, thereby improving braking performance and steering stability.

[0036] To achieve a good balance between braking performance and handling stability, the ratio of the ratio (Sa1 / Sa2) to the ratio (Sb1 / Sb2), ((Sa1 / Sa2) / (Sb1 / Sb2)), is preferably 1.1 or higher, more preferably 1.2 or higher, even more preferably 1.3 or higher, preferably 1.8 or lower, even more preferably 1.7 or lower, and even more preferably 1.6 or lower. In this case, the difference (θ2-θ1) between the angle θ1 of the first outer lateral groove 8A and the angle θ2 of the second outer lateral groove 8B is set to 20 to 50 degrees.

[0037] For example, the outer shoulder land portion 5A may not have a second outer transverse groove 8B, and only the first outer transverse groove 8A may be provided. In this case, the angle θ1 of the first outer transverse groove 8A is preferably 5 degrees or more, more preferably 10 degrees or more, preferably 45 degrees or less, and more preferably 30 degrees or less.

[0038] As shown in Figure 1, the first outer lateral groove 8A and the second outer lateral groove 8B are arranged alternately in the circumferential direction of the tire in this embodiment. This reduces the change in the circumferential stiffness of the outer shoulder land portion 5A, thereby maintaining turning performance.

[0039] The outer lateral groove 8 extends from the tire equator C toward the outer tread edge T1 towards the rearward side in the tire rotation direction R. In this embodiment, the first outer lateral groove 8A and the second outer lateral groove 8B each extend from the tire equator C toward the outer tread edge T1 towards the rearward side in the tire rotation direction R. Similarly, the inner lateral groove 9 extends from the tire equator C toward the inner tread edge T2 towards the rearward side in the tire rotation direction R. Such outer lateral grooves 8 and inner lateral grooves 9 can distribute braking force to both sides in the tire axial direction, thereby improving steering stability.

[0040] In this embodiment, the circumferential groove 3 includes an outer groove wall 31 on the outer tread end T1 side and an inner groove wall 32 on the inner tread end T2 side. A third chamfered portion 33 is formed on the outer groove wall 31. A fourth chamfered portion 34 is formed on the inner groove wall 32. In this embodiment, the outer groove wall 31 of the first circumferential groove 21, the second circumferential groove 22, and the third circumferential groove 23 is provided with a third chamfered portion 33, and the inner groove wall 32 of each is provided with a fourth chamfered portion 34. These third chamfered portions 33 and fourth chamfered portions 34 increase the contact area of ​​the tread surface 2a during either left or right turns, thereby improving braking performance during turns.

[0041] In cornering travel where the outer tread edge T1, which experiences a relatively large lateral force, is on the outside, both the outer groove wall 31 and the inner groove wall 32 deform to move towards the inner tread edge T2. In other words, during this cornering travel, the groove edge of the inner groove wall 32 moves towards the tread surface 2a, and the groove edge of the outer groove wall 31 moves towards the groove centerline of the circumferential groove 3 having the outer groove wall 31. As a result, the groove edge of the inner groove wall 32 is obstructed by the tread surface 2a and cannot deform smoothly, which is likely to lead to a reduction in the contact area. On the other hand, the groove edge of the outer groove wall 31, which moves towards the groove centerline, can deform relatively freely, thus suppressing the reduction in the contact area. Therefore, by making the virtual chamfer cross-sectional area S4 of the fourth chamfer portion 34 larger than the virtual chamfer cross-sectional area S3 of the third chamfer portion 33, the fourth chamfer portion 34 of the inner groove wall 32 can deform smoothly during the cornering travel, effectively suppressing the reduction in the contact area.

[0042] To further enhance these effects, it is desirable that the virtual chamfer cross-sectional area S4 of the fourth chamfer portion 34 be at least 1.1 times the virtual chamfer cross-sectional area S3 of the third chamfer portion 33. If the virtual chamfer cross-sectional area S4 is excessively larger than the virtual chamfer cross-sectional area S3, the area of ​​the tread surface 2a to which the inner groove wall 32 connects will decrease, and the tread rigidity may decrease excessively. Alternatively, the virtual chamfer cross-sectional area S3 of the third chamfer portion 33 may decrease, and the decrease in contact area during turning may not be suppressed. For this reason, it is even more desirable that the virtual chamfer cross-sectional area S4 be at least 1.15 times the virtual chamfer cross-sectional area S3, at least 1.3 times, and at least 1.25 times.

[0043] It is desirable that the virtual chamfer cross-sectional area S4a (not shown) of the fourth chamfer portion 34 of the first circumferential groove 21 be larger than the virtual chamfer cross-sectional area S4b (not shown) of the fourth chamfer portion 34 of the second circumferential groove 22. This significantly suppresses the decrease in tread rigidity of the land portion connected to the inner groove wall 32 of the first circumferential groove 21 during cornering, where the outer tread end T1, which is subjected to relatively large lateral forces, is on the outside of the turn. To effectively exert the above effect, it is desirable that the virtual chamfer cross-sectional area S4b of the fourth chamfer portion 34 of the second circumferential groove 22 be larger than the virtual chamfer cross-sectional area S4c (not shown) of the fourth chamfer portion 34 of the third circumferential groove 23.

[0044] The land ratio of the tread portion 2 located on the outer tread edge T1 side of the tire equator C is preferably 0.52 times or more, more preferably 0.55 times or more, more preferably 0.65 times or less, and more preferably 0.62 times or less than the land ratio of the tread portion located on the inner tread edge T2 side of the tire equator. In this specification, the land ratio is the ratio (R1 / R2) of the area R1 of the tread surface 2a to the area R2 of the virtual tread surface obtained by filling the circumferential grooves 3 and lateral grooves 4.

[0045] In this embodiment, the tread portion 2 has an asymmetrical tread pattern on both sides of the tire equator C. In such a tread pattern, the tread rigidity is not uniform between the tread portion 2 on the outer tread end T1 side and the tread portion 2 on the inner tread end T2 side. However, the tire 1 of the present invention is provided with first chamfered portions 13A and 13B on the first groove walls 10A and 10B of the outer lateral groove 8 and the inner lateral groove 9. Furthermore, in the tire 1 of the present invention, the virtual chamfered cross-sectional area So1 of the first chamfered portion 13A of the outer lateral groove 8 is larger than the virtual chamfered cross-sectional area Si1 of the first chamfered portion 13B of the inner lateral groove 9. This makes it possible to suppress the reduction in the contact area of ​​the tread tread surface 2a on the outer tread end T1 side, which is prone to deformation due to large lateral forces acting during cornering, and thus enables excellent braking performance during cornering.

[0046] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiments described above and can be implemented in various modified forms. [Examples]

[0047] A prototype tire with the basic pattern shown in Figure 1 was manufactured based on the specifications in Table 1. The braking performance of each test tire during cornering was then tested. The common specifications and test methods for each test tire are as follows. Outer shoulder land portion: Only the first outer transverse groove is provided. Si1: Same as in the examples and comparative examples.

[0048] <Braking performance during turns> Each test tire was fitted to all wheels of the test vehicle described below. A test driver drove the test vehicle on a test course with a dry asphalt surface. At this time, the braking performance, including stability and handling when braking while sharply turning the test vehicle, was evaluated subjectively by the test driver. The results are shown on a scale where Comparative Example 1 is rated at 100. A higher number indicates better performance. Tire size: 245 / 40R18 Rim: 18×8.5J Internal pressure (kPa): 230 (all wheels) Vehicle: Rear-wheel drive vehicle with a 2500cc engine displacement. The test results are shown in Table 1.

[0049] [Table 1]

[0050] The test results confirmed that the tires in the example have excellent braking performance during cornering.

[0051] [Note] The present invention includes the following embodiments.

[0052] [Invention 1] A tire having a tread portion, The tread portion has a specified orientation for mounting on the vehicle and a specified direction for tire rotation. The tread portion includes an outer tread end located on the outside of the vehicle when mounted on the vehicle, an inner tread end located on the inside of the vehicle when mounted on the vehicle, and a plurality of lateral grooves extending in the axial direction of the tire. The plurality of lateral grooves include outer lateral grooves positioned on the outer tread edge side of the tire equator and inner lateral grooves positioned on the inner tread edge side of the tire equator. The outer lateral groove and the inner lateral groove each include a first groove wall on the leading side in the tire rotation direction, A first chamfer is formed on at least a portion of the groove edge of each of the first groove walls. In the cross-section of the transverse groove, the virtual chamfer cross-sectional area So1 of the first chamfer of the outer transverse groove is larger than the virtual chamfer cross-sectional area Si1 of the first chamfer of the inner transverse groove. tire. [2nd Invention] The inner lateral groove and the outer lateral groove each include a second groove wall on the rearward side in the tire rotation direction, A second chamfer is formed on at least a portion of the groove edge of each of the second groove walls. The tire according to the present invention 1, wherein in the cross-section of the transverse groove, the virtual chamfer cross-sectional area Si1 of the first chamfer of the inner transverse groove is larger than the virtual chamfer cross-sectional area Si2 of the second chamfer of the inner transverse groove. [Invention 3] The tire according to the present invention, wherein the virtual chamfer cross-sectional area Si1 is 1.1 times or more the virtual chamfer cross-sectional area Si2. [4th Invention] The tire according to invention 2 or 3, wherein in the cross-section of the transverse groove, the virtual chamfer cross-sectional area So1 of the first chamfer of the outer transverse groove is larger than the virtual chamfer cross-sectional area So2 of the second chamfer of the outer transverse groove. [5th ​​Invention] The tire according to the present invention, wherein the virtual chamfer cross-sectional area So1 is 1.1 times or more the virtual chamfer cross-sectional area So2. [Invention 6] The tire according to claim 4 or 5 of the present invention, wherein in the cross-section of the transverse groove, the ratio of the virtual chamfer cross-sectional area So1 to the virtual chamfer cross-sectional area So2 (So1 / So2) is greater than the ratio of the virtual chamfer cross-sectional area Si1 to the virtual chamfer cross-sectional area Si2 (Si1 / Si2). [7th Invention] The outer lateral groove includes a first outer lateral groove having a first angle with respect to the tire axis and a second outer lateral groove having a second angle greater than that of the first outer lateral groove with respect to the tire axis. A tire according to any one of inventions 2 to 6, which satisfies the following relationship. Sa1 / Sa2>Sb1 / Sb2 Here, Sa1 is the virtual chamfer cross-sectional area of ​​the first chamfer of the first outer transverse groove, Sa2 is the virtual chamfer cross-sectional area of ​​the second chamfer of the first outer transverse groove, Sb1 is the virtual chamfer cross-sectional area of ​​the first chamfer of the second outer transverse groove, and Sb2 is the virtual chamfer cross-sectional area of ​​the second chamfer of the second outer transverse groove. [8th Invention] The tire according to the present invention, wherein the first outer lateral groove and the second outer lateral groove are arranged alternately in the circumferential direction of the tire. [Invention 9] The tire according to any one of invention 1 to 8, wherein the land ratio of the tread portion located on the outer tread edge side of the tire equator is 0.52 to 0.65 times the land ratio of the tread portion located on the inner tread edge side of the tire equator. [Explanation of Symbols]

[0053] 1 tire 2 Tread section 4 Yokomizo 8 Outer transverse groove 9. Inner transverse groove 10. First trench wall 10e groove edge 13. First chamfered section 14. First outer break Wa Width of the first land section Wb Width of the second continental section T1 Outer tread edge

Claims

1. A tire having a tread portion, The tread portion has a specified orientation for mounting on the vehicle and a specified direction for tire rotation. The tread portion includes an outer tread end located on the outside of the vehicle when mounted on the vehicle, an inner tread end located on the inside of the vehicle when mounted on the vehicle, and a plurality of lateral grooves extending in the axial direction of the tire. The plurality of lateral grooves include outer lateral grooves positioned on the outer tread edge side of the tire equator and inner lateral grooves positioned on the inner tread edge side of the tire equator. The outer lateral groove and the inner lateral groove each include a first groove wall on the leading side in the tire rotation direction, A first chamfer is formed on at least a portion of the groove edge of each of the first groove walls. In the cross-section of the transverse groove, the virtual chamfer cross-sectional area So1 of the first chamfer of the outer transverse groove is larger than the virtual chamfer cross-sectional area Si1 of the first chamfer of the inner transverse groove. tire.

2. The inner lateral groove and the outer lateral groove each include a second groove wall on the rearward side in the tire rotation direction. A second chamfer is formed on at least a portion of the groove edge of each of the second groove walls. The tire according to claim 1, wherein in the cross-section of the transverse groove, the virtual chamfer cross-sectional area Si1 of the first chamfer of the inner transverse groove is larger than the virtual chamfer cross-sectional area Si2 of the second chamfer of the inner transverse groove.

3. The tire according to claim 2, wherein the virtual chamfer cross-sectional area Si1 is 1.1 times or more the virtual chamfer cross-sectional area Si2.

4. The tire according to claim 2, wherein in the cross-section of the transverse groove, the virtual chamfer cross-sectional area So1 of the first chamfer of the outer transverse groove is larger than the virtual chamfer cross-sectional area So2 of the second chamfer of the outer transverse groove.

5. The tire according to claim 4, wherein the virtual chamfer cross-sectional area So1 is 1.1 times or more the virtual chamfer cross-sectional area So2.

6. The tire according to claim 4, wherein in the cross-section of the transverse groove, the ratio of the virtual chamfer cross-sectional area So1 to the virtual chamfer cross-sectional area So2 (So1 / So2) is greater than the ratio of the virtual chamfer cross-sectional area Si1 to the virtual chamfer cross-sectional area Si2 (Si1 / Si2).

7. The outer lateral groove includes a first outer lateral groove having a first angle with respect to the tire axis and a second outer lateral groove having a second angle greater than that of the first outer lateral groove with respect to the tire axis. The tire according to claim 2, satisfying the following relationship. Sa1 / Sa2>Sb1 / Sb2 Here, Sa1 is the virtual chamfer cross-sectional area of ​​the first chamfer of the first outer transverse groove, Sa2 is the virtual chamfer cross-sectional area of ​​the second chamfer of the first outer transverse groove, Sb1 is the virtual chamfer cross-sectional area of ​​the first chamfer of the second outer transverse groove, and Sb2 is the virtual chamfer cross-sectional area of ​​the second chamfered portion of the second outer transverse groove.

8. The tire according to claim 7, wherein the first outer lateral groove and the second outer lateral groove are arranged alternately in the circumferential direction of the tire.

9. The tire according to claim 1, wherein the land ratio of the tread portion located on the outer tread edge side of the tire equator is 0.52 to 0.65 times the land ratio of the tread portion located on the inner tread edge side of the tire equator.

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