Tire

Abstract

To provide a tire which can suppress damages and uneven wear of a land part, without impairing its excellent wet performance.SOLUTION: In a tire 1, a composite sipe 8 extending in a tire axial direction is provided on a land part 5. The composite sipe 8 includes a sipe body 9 having a pair of sipe wall surfaces, and a widening part 10 having a larger width than the sipe body 9. On at least one surface of the pair of sipe wall surfaces, a chamfered portion 12 composed of an inclined plane is formed on a tread 5a side of the land part 5.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Patent Document 1 below describes a pneumatic tire provided with sipes in a tread portion. The sipe is a composite sipe having a uniform width in the sipe depth direction and having a widened portion at an end in the sipe depth direction. A pneumatic tire having such a composite sipe is said to have excellent wet performance without impairing the uneven wear resistance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the pneumatic tire as described above, there is a problem that damage is likely to occur in the land portion near the portion where the composite sipe is provided.

[0005] The present invention has been devised in view of the above actual situation, and the main object thereof is to provide a tire capable of suppressing damage and uneven wear of the land portion without impairing the good wet performance due to the provision of the composite sipe.

Means for Solving the Problems

[0006] The present invention relates to a tire having a tread portion, wherein a land portion is provided on the tread portion, a composite groove extending in the tire axial direction is provided on the land portion, the composite groove includes a groove body extending radially inward in the tire radius direction from the tread surface of the land portion, and a widened portion connected to the inner side in the tire radius direction of the groove body and having a width larger than that of the groove body, the groove body has a pair of groove wall surfaces, and a chamfered portion formed of an inclined surface is formed on at least one of the pair of groove wall surfaces on the tread surface side.

[0007] It is desirable that, in the tire according to the present invention, the land portion is a shoulder land portion including a tread end.

[0008] It is desirable that, in the tire according to the present invention, the chamfered portion has a chamfering angle which is an angle between a virtual line obtained by extending the chamfered portion radially outward in the tire radius direction and the normal line of the tread surface, and the chamfering angle increases toward the outer side in the tire axial direction.

[0009] It is desirable that, in the tire according to the present invention, the chamfering angle continuously increases toward the outer side in the tire axial direction of the composite groove.

[0010] It is desirable that, in the tire according to the present invention, the chamfering angle is maximum at the outer end in the tire axial direction of the composite groove and minimum at the inner end in the tire axial direction of the composite groove.

[0011] It is desirable that, in the tire according to the present invention, the chamfering angle α1 at the outer end of the composite groove is 2 to 4 times the chamfering angle α2 at the inner end of the composite groove.

[0012] It is desirable that, in the tire according to the present invention, the rate of change in the tire axial direction of the length in the tire radius direction of the chamfered portion is smaller than the rate of change in the tire axial direction of the chamfering angle of the chamfered portion.

[0013] It is desirable that, in the tire according to the present invention, the chamfered portion is provided on each of the pair of groove wall surfaces.

[0014] It is desirable that the maximum width of the sipe body including the chamfered portion of the tire according to the present invention is 0.4 to 1.0 times the width of the widened portion.

[0015] It is desirable that the length of the chamfered portion of the tire according to the present invention in the tire radial direction is 10% to 20% of the depth of the composite sipe.

[0016] It is desirable that the tread portion of the tire according to the present invention includes a circumferential groove that is adjacent to the inner side of the land portion in the tire axial direction and extends continuously in the tire circumferential direction, and the composite sipe is connected to the circumferential groove.

Advantages of the Invention

[0017] By adopting the above configuration, the tire of the present invention can suppress damage and uneven wear of the land portion while taking advantage of the good wet performance due to the provision of the composite sipe.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0019] Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an enlarged plan view showing the tread portion 2 of the tire 1 of the present invention expanded. FIG. 1 shows the tread portion 2 of a pneumatic tire for a passenger car. However, the present invention may be applied to tires for heavy loads and other categories of tires.

[0020] As shown in FIG. 1, a land portion 5 is provided in the tread portion 2 of the present embodiment. The land portion 5 includes a tread surface 5a. The tread surface 5a is a region that contacts the plane in the normal load-bearing state. The "normal load-bearing state" means a state in which the tire 1 is rim-mounted on a normal rim (not shown) at a normal internal pressure, a normal load is applied, and the tire is grounded on the plane at a camber angle of 0 degrees. In FIG. 1, the right side is the outer side in the tire axial direction.

[0021] The "normal rim" is the rim defined for each tire in the standard system including the standards on which the tire is based. For example, in JATMA, it is the "standard rim", in TRA, it is the "Design Rim", and in ETRTO, it is the "Measuring Rim".

[0022] The "normal internal pressure" is the air pressure defined for each tire in the standard system including the standards on which the tire is based. In JATMA, it is the "maximum air pressure", in TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in ETRTO, it is the "INFLATION PRESSURE".

[0023] The "normal load" is the load defined for each tire in the standard system including the standards on which the tire is based. In JATMA, it is the "maximum load capacity", in TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in ETRTO, it is the "LOAD CAPACITY".

[0024] The land part 5 is provided with a composite sip 8 extending in the tire axial direction. FIG. 2 is a perspective view of the land part 5 of FIG. 1. As shown in FIGS. 1 and 2, the composite sip 8 of the present embodiment includes a sip body 9 extending inward in the tire radial direction from the tread surface 5a, and an enlarged width part 10 connected to the inner side of the sip body 9 in the tire radial direction and having a larger width than the sip body 9. Such a composite sip 8 has good wet performance. In this specification, the enlarged width part 10 and the sip body 9 are divided at the inner end in the tire radial direction where the width is minimized toward the outer side in the tire radial direction.

[0025] FIG. 3(a) is a cross-sectional view taken along line A-A of FIG. 1. FIG. 3(b) is a cross-sectional view taken along line B-B of FIG. 1. As shown in FIGS. 1 to 3, the sip body 9 has a pair of sip wall surfaces 11, 11. At least one of the pair of sip wall surfaces 11 is formed with a chamfered part 12 having an inclined surface on the tread surface 5a side. Such a composite sip 8 can suppress the collapse of the land part 5 following the chamfered part 12 during braking or acceleration, and generate a uniform ground pressure. Thereby, damage and uneven wear of the land part 5 that are likely to occur near the composite sip 8 are suppressed. The "inclined surface" refers to a surface inclined at an angle smaller than the sip wall surface 11 with respect to the tread surface 5a.

[0026] FIG. 4 is a plan view of the tread part 2. As shown in FIG. 4, the tread part 2 is provided with, for example, a pair of crown circumferential grooves 3a, 3a arranged on both sides of the tire equator C, and a pair of shoulder circumferential grooves 3b, 3b arranged between each crown circumferential groove 3a and the tread end Te. The crown circumferential grooves 3a and the shoulder circumferential grooves 3b each extend continuously in the tire circumferential direction.

[0027] The tread end Te is defined as the grounding position farthest outside in the tire axial direction in the normal load state. Also, in this specification, unless otherwise specified, the dimensions and the like of each part of the tire 1 are values measured in the normal state.

[0028] The land portion 5 includes a crown land portion 5A divided by a pair of crown circumferential grooves 3a, a pair of middle land portions 5B divided by the crown circumferential groove 3a and the shoulder circumferential groove 3b, and a pair of shoulder land portions 5C divided by the shoulder circumferential groove 3b and the tread edge Te. In other words, the shoulder circumferential groove 3b is provided adjacent to the inner side in the tire axial direction of the shoulder land portion 5C.

[0029] Each shoulder land portion 5C has a width Ws in the tire axial direction that is, for example, larger than the widths Wc and Wm in the tire axial direction of the crown land portion 5A and the middle land portion 5B. Thereby, the lateral rigidity of the shoulder land portion 5C where a large lateral force acts during turning is increased, so that uneven wear and damage to the land portion 5 are suppressed.

[0030] Although not particularly limited, the width Ws of the shoulder land portion 5C is preferably 1.5 times or more, more preferably 1.7 times or more, preferably 2.5 times or less, and more preferably 2.3 times or less the widths Wc of the crown land portion 5A and Wm of the middle land portion 5B. The width Ws of the shoulder land portion 5C is desirably 15% to 25% of the tread width TW. The tread width TW is the distance in the tire axial direction between the tread edges Te on both sides.

[0031] In this specification, the shoulder land portion 5C on one side (the right side in the figure) in the tire axial direction is defined as the first shoulder land portion 5r, and the shoulder land portion 5C on the other side (the left side in the figure) in the tire axial direction is defined as the second shoulder land portion 5s. Also, in this specification, the middle land portion 5B on one side in the tire axial direction is defined as the first middle land portion 5u, and the middle land portion 5B on the other side in the tire axial direction is defined as the second middle land portion 5v.

[0032] In the present embodiment, the compound sipe 8 is provided in one of the shoulder land portions 5C. The compound sipe 8 is provided, for example, in the first shoulder land portion 5r and not in the second shoulder land portion 5s. Note that the compound sipe 8 may be provided in the second shoulder land portion 5s and not in the first shoulder land portion 5r.

[0033] In the case of the tread portion 2 with the specified vehicle-mounted orientation, it is more desirable that the composite sipe 8 be provided on the shoulder land portion 5C on the outer side of the vehicle where a greater lateral force acts during turning. Further, the composite sipe 8 may be provided on the shoulder land portions 5C on both sides (not shown).

[0034] The composite sipe 8 is connected to, for example, the shoulder circumferential groove 3b. Further, in this embodiment, the composite sipe 8 extends beyond the tread end Te. Such a composite sipe 8 enhances drainage performance and improves wet performance.

[0035] In this embodiment, the composite sipe 8 extends along the tire axial direction. In this specification, the phrase "along the tire axial direction" refers to a mode in which the angle θ1 of the virtual straight line c1 connecting the inner end 8i in the tire axial direction of the composite sipe 8 and the position of the tread end Te of the composite sipe 8 with respect to the tire axial direction is 10 degrees or less.

[0036] As shown in FIG. 3, in this embodiment, the pair of sipe wall surfaces 11, 11 extend parallel to each other in the tire axial direction and the tire radial direction. Such a sipe body 9 reduces the change in pattern stiffness of the shoulder land portion 5C.

[0037] The width W1 of the sipe body 9 is preferably, for example, 0.5 mm to 0.7 mm. Such a sipe body 9 helps to smoothly suck up the water film between the road surface and the tread surface 5a and suppresses uneven wear and damage to the land portion 5.

[0038] In this embodiment, the chamfered portion 12 is formed of a planar inclined surface. The term "planar" includes a mode in which the entire inclined surface is formed of a plane. Further, the "planar" includes a mode in which at least one of the connection portion J1 between the inclined surface and the tread surface 5a and the connection portion J2 between the inclined surface and the sipe wall surface 11 is formed in an arc shape convex toward the center line 8c side of the composite sipe 8 in the manufacturing accuracy of the tire 1. Note that the entire inclined surface of the chamfered portion 12 may be formed in an arc shape convex toward the center line 8c side (not shown).

[0039] In the present embodiment, the chamfered portion 12 is provided on each of the pair of side walls 11. Thereby, during braking and acceleration, the collapse of the land portion 5 following both sides in the tire circumferential direction of the compound sipe 8 is suppressed.

[0040] The chamfered portion 12 has a chamfer angle α (shown in FIG. 2), which is the angle between the virtual line 12k obtained by extending the chamfered portion 12 outward in the tire radial direction and the normal line n of the tread surface 5a. And in the present embodiment, the chamfer angle α increases toward the outside in the tire axial direction. Thereby, the ground contact performance on the outside in the tire axial direction where a large lateral force acts during turning running is enhanced, so that a more uniform ground contact pressure is generated, and the effect of suppressing damage and uneven wear of the land portion 5 is increased.

[0041] As shown in FIGS. 1 to 4, for example, the chamfer angle α continuously increases toward the outside in the tire axial direction. Thereby, the above-described action is more effectively exerted. In the present embodiment, the chamfer angle α is maximum at the outer end 8e in the tire axial direction of the compound sipe 8 and minimum at the inner end 8i in the tire axial direction of the compound sipe 8. Thereby, the uniformity is enhanced between both ends in the tire axial direction of the shoulder land portion 5C, and the damage resistance performance and uneven wear resistance performance are improved. In this specification, when the compound sipe 8 is provided on the shoulder land portion 5C, the outer end 8e of the compound sipe 8 can be set at a position on the tread end Te. Note that, from the viewpoint of enhancing the ground contact performance on the outside in the tire axial direction of the land portion 5, for example, the chamfer angle α may increase stepwise toward the outside in the tire axial direction (not shown).

[0042] It is desirable that the chamfer angle α1 at the outer end 8e of the compound sipe 8 is 2 times or more, more desirably 2.5 times or more, 4 times or less, and more desirably 3.5 times or less of the chamfer angle α2 at the inner end 8i of the compound sipe 8. Since the chamfer angle α1 at the outer end 8e is 2 times or more and 4 times or less of the chamfer angle α2 at the inner end 8i, the uniformity of the ground contact pressure can be enhanced. Further, for example, the chamfer angle α2 at the inner end 8i is desirably 8 degrees or more, more desirably 10 degrees or more, desirably 37 degrees or less, and more desirably 35 degrees or less.

[0043] The change rate K1 of the tire radial length H1 of the chamfered portion 12 is, for example, smaller than the change rate K2 of the chamfering angle α of the chamfered portion 12. Such a chamfered portion 12 can maintain high uniformity of the contact pressure while keeping the change in the tire radial rigidity (vertical rigidity) of the shoulder land portion 5C small. The change rate K1 is the ratio (mm / mm) of the change (mm) in the length H1 per unit length (mm) in the tire axial direction of the composite groove 8. The change rate K2 is the ratio (deg / mm) of the change (degrees) in the chamfering angle α per unit length (mm) in the tire axial direction of the composite groove 8.

[0044] In the present embodiment, the chamfered portion 12 has a constant length portion 16 in which the tire radial length H1 is the same along the tire axial direction. Such a constant length portion 16 reduces the change rate K1, thereby effectively exerting the above-described effects. The constant length portion 16 is formed, for example, to extend from the inner end 8i of the composite groove 8 to the tread end Te. Note that the constant length portion 16 may be formed to extend from the inner end 8i of the composite groove 8 to the outer end 8e outside the tread end Te.

[0045] The length H1 of the chamfered portion 12 is desirably 10% or more of the depth D1 of the composite groove 8, more desirably 12% or more, desirably 20% or less, and more desirably 18% or less. Since the length H1 of the chamfered portion 12 is 10% or more of the depth D1 of the composite groove 8, the above-mentioned collapse of the land portion 5 is effectively suppressed. Since the length H1 of the chamfered portion 12 is 20% or less of the depth D1 of the composite groove 8, an excessive decrease in the rigidity of the shoulder land portion 5C is suppressed. The depth D1 of the composite groove 8 is desirably, for example, 5.5 to 7.5 mm.

[0046] The maximum width W2 of the sip body 9 including the chamfered portion 12 is desirably 0.4 times or more, more desirably 0.5 times or more, desirably 1.0 times or less, and more desirably 0.9 times or less of the width Wa of the widened portion 10. Since the maximum width W2 of the sip body 9 is 0.4 times or more of the width Wa of the widened portion 10, the effect of suppressing the tilting of the land portion 5 is enhanced, and the uniformity of the ground pressure is improved. Since the maximum width W2 of the sip body 9 is 1.0 times or less of the width Wa of the widened portion 10, excessive rigidity reduction of the land portion 5 is suppressed. In the composite sip 8 of the present embodiment, at the tread edge Te, the maximum width W2 is 1.0 times the width Wa of the widened portion 10. The composite sip 8 may have a maximum width W2 of 1.0 times the width Wa of the widened portion 10 at the outer end 8e outside the tread edge Te.

[0047] The cross-section of the widened portion 10 is, for example, an elliptical shape. Such a widened portion 10 suppresses a reduction in the rigidity of the land portion 5 and suppresses uneven wear and damage to the land portion 5. In order to effectively exhibit such an action, the length H2 of the widened portion 10 in the tire radial direction is desirably 1.2 times or more, more desirably 1.3 times or more, desirably 1.6 times or less, and more desirably 1.5 times or less of the width Wa of the widened portion 10.

[0048] The cross-sectional area As of the widened portion 10 is formed to have the same size, for example, toward the outside in the tire axial direction. Such a widened portion 10 suppresses a local change in the rigidity of the land portion 5, so the damage resistance performance and uneven wear resistance performance are improved. In the present embodiment, the cross-sectional area As of the widened portion 10 is formed to have the same size from the inner end 8i to the tread edge Te of the composite sip 8. The cross-sectional area As of the widened portion 10 may be formed to have the same size, for example, from the inner end 8i to the outer end 8e outside the tread edge Te of the composite sip 8. Note that in order to maintain a high rigidity of the portion on the outer side in the tire axial direction where a large lateral force acts during turning travel, the cross-sectional area As of the widened portion 10 may be increased toward the outer side in the tire axial direction.

[0049] Although not particularly limited, the length H2 of the widened portion 10 in the tire radial direction is desirably at least 0.3 times, more desirably at least 0.4 times, desirably at most 0.7 times, and more desirably at most 0.6 times the depth D1 of the composite sipe 8.

[0050] As shown in FIGS. 1 and 4, in the first shoulder land portion 5r where the composite sipe 8 is provided, a first shoulder cross groove 21 extending in the tire axial direction is further provided. The first shoulder cross groove 21 extends, for example, from the shoulder circumferential groove 3b outward in the tire axial direction beyond the tread end Te. Such a first shoulder cross groove 21 enhances wet performance.

[0051] FIG. 5(a) is a cross-sectional view taken along line C-C of FIG. 1. FIG. 5(b) is a cross-sectional view taken along line D-D of FIG. 1. As shown in FIG. 5, the first shoulder cross groove 21 of the present embodiment includes a groove bottom 21a and a pair of wall portions 21b, 21b extending outward in the tire radial direction from both sides of the groove bottom 21a. The first shoulder cross groove 21 also includes a first chamfered portion 21c that connects the tread surface 5a and the wall portion 21b with a gentle slope. In this way, in the present embodiment, the first shoulder land portion 5r has the composite sipe 8 and the first shoulder cross groove 21 each having a chamfered portion 12, 21c, so that the contact pressure of the shoulder land portion 5C becomes more uniform.

[0052] Each of the pair of wall portions 21b of the present embodiment is inclined toward the groove center line 21s side in the outer direction of the tire radial direction. In other words, in the wall portion 21b, the groove width W3 of the first shoulder cross groove 21 becomes smaller in the outer direction of the tire radial direction.

[0053] In the present embodiment, the first chamfered portion 21c is inclined in a direction away from the groove center line 21s toward the outer side in the tire radial direction. The first chamfered portion 21c is formed, for example, in an arc shape convex toward the outer side in the tire radial direction.

[0054] The first shoulder transverse groove 21 includes, for example, a constant-width portion 21A that extends from the shoulder circumferential groove 3b toward the inner side in the tire axial direction with the same groove width W4, and a width-reducing portion 21B between the constant-width portion 21A and the tread edge Te where the groove width W4 continuously decreases toward the outer side in the tire axial direction. The groove width W4 of the first shoulder transverse groove 21 is, in this specification, the length on the tread surface 5a including the first chamfered portion 21c.

[0055] The groove depth D2 of the first shoulder transverse groove 21 is preferably greater than the depth D1 of the composite sipe 8. Although not particularly limited, the depth D1 of the composite sipe 8 is preferably 85% or more, more preferably 87% or more, preferably 95% or less, and more preferably 93% or less of the groove depth D2 of the first shoulder transverse groove 21.

[0056] FIG. 6 is a plan view of the tread portion 2. As shown in FIG. 6, a second shoulder land portion 5s of the present embodiment is provided with a second shoulder transverse groove 23 and a second shoulder sipe 24. In this specification, the “sipe” is a cut-like body with a width of less than 1.5 mm, and is clearly distinguished from the “groove” with a groove width of 1.5 mm or more such as a circumferential groove or a transverse groove.

[0057] The second shoulder transverse groove 23 includes a pair of groove walls 23a, 23a that extend outward in the tire radial direction from the groove bottom, and a pair of second chamfered portions 23b that connect each groove wall 23a and the tread surface 5a with an inclined surface.

[0058] The second chamfered portion 23b includes a width-increasing portion 25a where the chamfer width W5 increases toward the outer side in the tire axial direction, and a width-reducing portion 25b that continues to the width-increasing portion 25a and where the chamfer width W5 decreases toward the outer side in the tire axial direction.

[0059] On one side in the tire circumferential direction (upper side in the figure) of the second shoulder lateral groove 23, the second chamfered portion 23A is formed such that the length in the tire axial direction of the width increasing portion 25a is larger than the length in the tire axial direction of the width decreasing portion 25b. Also, on the other side in the tire circumferential direction (lower side in the figure) of the second shoulder lateral groove 23, the second chamfered portion 23B is formed such that the length in the tire axial direction of the width increasing portion 25a is smaller than the length in the tire axial direction of the width decreasing portion 25b.

[0060] In the present embodiment, the second shoulder lateral groove 23 and the second shoulder sipe 24 extend from the shoulder circumferential groove 3b to the outside in the tire axial direction beyond the tread end Te. The second shoulder lateral groove 23 and the second shoulder sipe 24 of the present embodiment extend along the tire axial direction. The second shoulder sipe 24 is inclined, for example, in the same direction as the second shoulder lateral groove 23 with respect to the tire axial direction.

[0061] In the present embodiment, the first middle land portion 5u includes the first middle lateral groove 30 and the first middle sipe 31. The first middle lateral groove 30 and the first middle sipe 31 are inclined in the same direction with respect to the tire axial direction. The first middle lateral groove 30 and the first middle sipe 31 are connected to the shoulder circumferential groove 3b and the crown circumferential groove 3a.

[0062] In the present embodiment, the second middle land portion 5v includes the outer lateral groove 33 extending from the shoulder circumferential groove 3b, the inner lateral groove 34 extending from the crown circumferential groove 3a, and the middle sipe 35.

[0063] The outer lateral groove 33 includes, for example, a first outer lateral groove 33A that terminates at the second middle land portion 5v without connecting to other lateral grooves or sipers, and a second outer lateral groove 33B that is connected to the middle sipe 35. In the present embodiment, the inner lateral groove 34 is inclined in the same direction as the outer lateral groove 33 with respect to the tire axial direction. In the present embodiment, the middle sipe 35 includes a communicating middle sipe 35A that is connected to the first outer lateral groove 33A and the inner lateral groove 34, and a terminating middle sipe 35B that extends from the crown circumferential groove 3a and terminates at the second middle land portion 5v without connecting to other sipers or grooves.

[0064] In the present embodiment, the first shoulder land portion 5r and the second shoulder land portion 5s are each formed in a different pattern shape. Note that the first shoulder land portion 5r and the second shoulder land portion 5s are not limited to such a mode, and they may each have the same pattern shape. Also, in the present embodiment, the first middle land portion 5u and the second middle land portion 5v are each formed in a different pattern shape, but for example, they may each have the same pattern shape.

[0065] The crown land portion 5A includes a crown transverse groove 38 and a crown sipe 39 in the present embodiment. The crown transverse groove 38 and the crown sipe 39 terminate at the crown land portion 5A without connecting to other grooves or sipes, for example. The crown transverse groove 38 extends from the crown circumferential groove 3a on one side in the tire axial direction (right side in the figure) across the tire equator C in the present embodiment. The crown sipe 39 includes, for example, a first crown sipe 39A extending from the crown circumferential groove 3a on the other side and a second crown sipe 39B extending from the crown circumferential groove 3a on the one side. The crown transverse groove 38 and the crown sipe 39 are inclined in the same direction with respect to the tire axial direction, for example.

[0066] As described above, the particularly preferred embodiments of the present invention have been described in detail. However, the present invention is not limited to the illustrated embodiments and can be implemented in various modes.

Example

[0067] A tire having the basic pattern of FIG. 4 was prototyped. Then, the dry performance, wet performance, snow performance, and damage resistance performance of each test tire were tested. The common specifications and test methods of each test tire are as follows.

[0068] <Wet performance, uneven wear resistance performance, and damage resistance performance> Each test tire was mounted on all the wheels of a passenger car (engine displacement: 2400 cc) under the following conditions. Then, a test driver drove the vehicle on a test course on a wet asphalt road surface, and the degrees of steering operability, high-speed stability, and stability during braking at that time were evaluated by the test driver's senses. Also, after this driving, the occurrence status of uneven wear, cracks, etc. was evaluated by the test driver's senses. The results are shown in scores with Comparative Example 1 set as 100. For each performance, the larger the numerical value, the better. Size, rim, inner pressure: 215 / 60R16, 16×6.5, 240 kPa The test results are shown in Table 1. "※1" in Table 1 means the value at the inner end of the composite sipes. The same "※2" means the value at the tread edge Te.

[0069]

Table 1

[0070] As a result of the test, it is understood that the tires of the examples have good wet performance while suppressing damage and uneven wear of the land portion compared to the tires of the comparative examples.

[0071] 1 Tire 5 Land portion 5a Tread 8 Composite sipes 9 Sipes body 10 Width portion 11 Sipes wall surface 12 Chamfered portion

Claims

1. A tire having a tread portion, wherein a land portion is provided in the tread portion, and a composite sipe extending in the tire axial direction is provided in the land portion, the composite sipe including a sipe body extending radially inward in the tire radius direction from the tread surface of the land portion, and a widened portion connected to the inner side of the sipe body in the tire radius direction and having a width larger than that of the sipe body, the sipe body having a pair of sipe wall surfaces, wherein a chamfered portion formed of an inclined surface is formed on at least one of the pair of sipe wall surfaces on the tread surface side, the chamfered portion having a chamfering angle which is an angle between a virtual line obtained by extending the chamfered portion radially outward in the tire radius direction and the normal line of the tread surface, the chamfering angle increasing toward the outer side in the tire axial direction, the chamfering angle being maximum at the outer end in the tire axial direction of the composite sipe and minimum at the inner end in the tire axial direction of the composite sipe, wherein the chamfering angle α1 at the outer end of the composite sipe is 2 to 4 times the chamfering angle α2 at the inner end of the composite sipe, a tire.

2. The tire according to claim 1, wherein the land portion is a shoulder land portion including a tread end.

3. The tire according to claim 1 or 2, wherein the chamfering angle continuously increases toward the outer side in the tire axial direction of the composite sipe.

4. The tire according to any one of claims 1 to 3, wherein the rate of change in the tire axial direction of the length in the tire radius direction of the chamfered portion is smaller than the rate of change in the tire axial direction of the chamfering angle of the chamfered portion.

5. The tire according to any one of claims 1 to 4, wherein the chamfered portion is provided on each of the pair of sipe wall surfaces.

6. The tire according to any one of claims 1 to 5, wherein the maximum width of the sipe body including the chamfered portion is 0.4 to 1.0 times the width of the widened portion.

7. The tire according to any one of claims 1 to 6, wherein the length in the tire radius direction of the chamfered portion is 10% to 20% of the depth of the composite sipe.

8. The tread portion includes a circumferential groove continuously extending in the tire circumferential direction adjacent to the inner side in the tire axial direction of the land portion, the tire according to any one of claims 1 to 7, wherein the composite sipe is connected to the circumferential groove.

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