tire

Abstract

To provide a tire in which a tread part is divided into four land parts, and which is improved in wear resistance performance and wet performance.SOLUTION: A tire comprises a tread part 2. The tread part 2 is constituted of three circumferential grooves 3 and four land parts 4. A first crown land part 11 is provided with a first full open sipe 16, a first semi-open sipe 18, and a second semi-open sipe 19. The first semi-open sipe 18 and the second semi-open sipe 19 are inclined in a first direction with respect to a tire axial direction. An angle of the second semi-open sipe 19 is larger than an angle of the first semi-open sipe 18. The second semi-open sipe 19 is a chamfered sipe. A first sipe wall 23 of the second semi-open sipe 19 includes a main body surface 23a and an inclined surface 23b. A second sipe wall 24 of the second semi-open sipe 19 is connected to a tread surface of the first crown land part 11 without being chamfered.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to tires. [Background technology]

[0002] Patent Document 1 below proposes a pneumatic tire in which the tread portion is divided into four land portions, and the center land portion is provided with a plurality of center lateral grooves. The pneumatic tire is expected to improve steering stability and noise performance by improving the center lateral grooves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-073706 Summary of the Invention [Problem to be solved by the invention]

[0004] Tires with a tread portion divided into four land portions by three circumferential grooves, such as the pneumatic tire of Patent Document 1, have room for improvement in wet performance. Furthermore, such tires tend to have a high ground contact pressure acting on each land portion, and there is also room for improvement in wear resistance.

[0005] The present disclosure has been devised in consideration of the above-described circumstances, and has as its main object to improve the wear resistance and wet performance of a tire whose tread portion is divided into four land portions. [Means for solving the problem]

[0006] The present disclosure relates to a tire having a tread portion, the tread portion being composed of three circumferential grooves extending continuously in the tire circumferential direction between a first tread edge and a second tread edge, and four land portions divided by the three circumferential grooves, the three circumferential grooves including a first shoulder circumferential groove provided between the first tread edge and the tire equator, and a crown circumferential groove adjacent to the first shoulder circumferential groove on the tire equator side, the four land portions including a first crown land portion divided between the first shoulder circumferential groove and the crown circumferential groove, the first crown land portion including at least one first full-open sipe completely traversing the first crown land portion in the tire axial direction, at least one first semi-open sipe communicating with the first shoulder circumferential groove and having an interrupted end within the first crown land portion, and at least one first semi-open sipe communicating with the crown circumferential groove and having an interrupted end within the first crown land portion. and a second semi-open sipe having a width greater than that of the first semi-open sipe, the first semi-open sipe and the second semi-open sipe being inclined in a first direction with respect to the tire axial direction, the angle of the second semi-open sipe with respect to the tire axial direction being larger than the angle of the first semi-open sipe with respect to the tire axial direction, the second semi-open sipe being a chamfered sipe including a sipe main body portion having a width extending in the tire radial direction and having a width greater than that of the sipe main body portion and opening to the tread surface of the first crown land portion, the second semi-open sipe including a first sipe wall continuing to a groove wall of the crown circumferential groove and forming an obtuse-angled corner portion, and a second sipe wall opposite to the first sipe wall, the first sipe wall including a main body surface that forms the sipe main body portion and an inclined surface that forms the chamfered portion, and the second sipe wall being connected to the tread surface of the first crown land portion without being chamfered. [Effects of the Invention]

[0007] By adopting the above-described configuration, the tire of the present disclosure can exhibit excellent wear resistance and wet performance. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a development view of a tread portion of a tire according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is an enlarged view of a first crown land portion and a second crown land portion of FIG. [Figure 3] 3 is an enlarged view of a first full-open sipe, a first semi-open sipe, and a second semi-open sipe in FIG. 2. FIG. [Figure 4] FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 5] FIG. 3 is a cross-sectional view taken along line BB in FIG. 2. [Figure 6] FIG. 3 is a cross-sectional view taken along line CC in FIG. 2. [Figure 7] FIG. 2 is an enlarged view of the first shoulder land portion of FIG. 1. [Figure 8] FIG. 9 is a cross-sectional view taken along the line DD in FIG. 8. [Figure 9] FIG. 2 is an enlarged view of the second shoulder land portion of FIG. 1. [Figure 10] FIG. 4 is an enlarged view of a first crown land portion of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present disclosure will be described below with reference to the drawings. Fig. 1 is a development view of a tread portion 2 of a tire 1 showing an embodiment of the present disclosure. The tire 1 of this embodiment is suitably used, for example, as a pneumatic tire for passenger cars. However, the present disclosure is not limited to such an embodiment and may also be applied to pneumatic tires for heavy loads and non-pneumatic tires that are not filled with pressurized air inside the tire.

[0010] 1, the tread portion 2 of the tire 1 of this embodiment has a specified orientation for mounting on a vehicle. As a result, the tread portion 2 includes a first tread edge T1 intended to be on the inside of the vehicle when mounted on the vehicle, and a second tread edge T2 intended to be on the outside of the vehicle when mounted on the vehicle. However, the tire 1 of the present disclosure is not limited to this configuration, and may have, for example, an orientation for mounting on a vehicle that is not specified.

[0011] The first tread edge T1 and the second tread edge T2 each correspond to the edge of the contact patch when 70% of the normal load is applied to the tire 1 in its normal state and the tread portion 2 is brought into contact with a flat surface at a camber angle of 0°.

[0012] "Normal condition" means, in the case of a pneumatic tire for which various standards are established, that the tire is mounted on a normal rim, inflated to the normal internal pressure, and is in an unloaded state. In the case of a tire for which various standards are not established or a non-pneumatic tire, the normal condition means a standard use state according to the intended use of the tire, in which the tire is not mounted on a vehicle and is unloaded. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal condition.

[0013] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "design rim," and in the case of ETRTO, it is called a "measuring rim."

[0014] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard on which the tire is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0015] For pneumatic tires for which various standards are established, "normal load" refers to the load specified for each tire in the standard system including the standard on which the tire is based. For JATMA, this is "maximum load capacity," for TRA, this is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, this is "LOAD CAPACITY." For tires for which various standards are not established, "normal load" refers to the maximum load that can be applied when using the tire in accordance with the above standards.

[0016] The tread portion 2 is configured with three circumferential grooves 3 extending continuously in the tire circumferential direction between the first tread edge T1 and the second tread edge T2, and four land portions 4 divided by the three circumferential grooves 3. In other words, the tire 1 of the present disclosure is a so-called four-rib tire.

[0017] The circumferential grooves 3 include a first shoulder circumferential groove 5, a second shoulder circumferential groove 6, and a crown circumferential groove 7. Of the multiple circumferential grooves 3, the first shoulder circumferential groove 5 is arranged closest to the first tread edge T1. Of the multiple circumferential grooves 3, the second shoulder circumferential groove 6 is arranged closest to the second tread edge T2. The crown circumferential groove 7 is provided between the first shoulder circumferential groove 5 and the second shoulder circumferential groove 6, and in this embodiment, is provided on the tire equator C.

[0018] The axial distance L1 from the tire equator C to the groove center line of the first shoulder circumferential groove 5 or the second shoulder circumferential groove 6 is preferably, for example, 15% to 30% of the tread width TW. The tread width TW is the axial distance from the first tread edge T1 to the second tread edge T2 in the normal state.

[0019] Each circumferential groove 3 of this embodiment extends, for example, linearly in parallel to the tire circumferential direction. Each circumferential groove 3 may extend, for example, in a wavy shape.

[0020] The groove width W1 of each circumferential groove 3 is preferably at least 3 mm or more. Furthermore, the groove width W1 of each circumferential groove 3 is preferably 3.0% to 8.0% of the tread width TW. As a more preferable aspect in this embodiment, of the three circumferential grooves 3, the first shoulder circumferential groove 5 has the smallest groove width. However, the present disclosure is not limited to this aspect.

[0021] The four land portions 4 include at least a first crown land portion 11 defined between the first shoulder circumferential groove 5 and the crown circumferential groove 7. The four land portions 4 in this embodiment also include a second crown land portion 12, a first shoulder land portion 13, and a second shoulder land portion 14. The second crown land portion 12 is defined between the second shoulder circumferential groove 6 and the crown circumferential groove 7. The first shoulder land portion 13 is defined axially outward of the first shoulder circumferential groove 5 and includes the first tread edge T1. The second shoulder land portion 14 is defined axially outward of the second shoulder circumferential groove 6 and includes the second tread edge T2.

[0022] Fig. 2 shows an enlarged view of the first crown land portion 11 and the second crown land portion 12. As shown in Fig. 2, the first crown land portion 11 is provided with at least one first full-open sipe 16, one first semi-open sipe 18, and one second semi-open sipe 19. The first crown land portion 11 of this embodiment is provided with a plurality of these sipes.

[0023] The first full-open sipe 16 completely crosses the first crown land portion 11 in the tire axial direction. The first semi-open sipe 18 communicates with the first shoulder circumferential groove 5 and has an interrupted end 18a within the first crown land portion 11. The second semi-open sipe 19 communicates with the crown circumferential groove 7 and has an interrupted end 19a within the first crown land portion 11.

[0024] In this specification, the term "sipe" refers to a small cut in the sipe body, where the width between two sipe walls is 1.5 mm or less. The term "sipe body" also refers to a portion where two sipe walls extend substantially parallel to each other in the tire radial direction. "Substantially parallel" refers to an aspect where the angle between the two sipe walls is 10° or less. As described below, the sipe may include a chamfered portion. The sipe may also have a so-called flask bottom, where the width is expanded at the bottom.

[0025] Fig. 3 shows an enlarged view of the first full-open sipe 16, the first semi-open sipe 18, and the second semi-open sipe 19. As shown in Fig. 3, the first semi-open sipe 18 and the second semi-open sipe 19 are inclined in a first direction (upward to the right in each drawing in this specification) with respect to the tire axial direction. In addition, the angle θ2 of the second semi-open sipe 19 with respect to the tire axial direction is larger than the angle θ1 of the first semi-open sipe 18 with respect to the tire axial direction. Note that in this specification, the angle of the sipe with respect to the tire axial direction is measured at the center line of the sipe main body.

[0026] Fig. 4 shows a cross-sectional view taken along line AA in Fig. 2. As shown in Fig. 4, the second semi-open sipe 19 is a chamfered sipe that includes a sipe main body 20 having a width extending in the tire radial direction of 1.5 mm or less, and a chamfered portion 21 that has a width greater than the width of the sipe main body 20 and opens to the tread surface of the first crown land portion 11.

[0027] The second semi-open sipe 19 includes a first sipe wall 23 and a second sipe wall 24. The first sipe wall 23 is a sipe wall that is continuous with the groove wall of the crown circumferential groove 7 and forms an obtuse corner portion in a tread plan view. The second sipe wall 24 is a sipe wall that is continuous with the groove wall of the crown circumferential groove 7 and forms an acute corner portion in a tread plan view.

[0028] The first sipe wall 23 includes a main body surface 23a that constitutes the sipe main body portion 20 and an inclined surface 23b that constitutes the chamfered portion 21. The second sipe wall 24 is connected to the tread surface of the first crown land portion 11 without being chamfered. By adopting the above-described configuration, the tire 1 of the present disclosure can exhibit excellent wear resistance and wet performance. The following mechanism is presumed to be the reason for this.

[0029] The first full-open sipes 16, the first semi-open sipes 18, and the second semi-open sipes 19 provide friction on wet roads while suppressing excessive reduction in rigidity of the land portions. This improves wear resistance and wet performance. In addition, because the first semi-open sipes 18 and the second semi-open sipes 19 are inclined in the first direction with respect to the tire axial direction, they can also provide friction in the tire axial direction when driving on wet roads.

[0030] On the other hand, the second semi-open sipes 19 are disposed on the crown circumferential groove 7 side, and therefore are subjected to a large ground contact pressure. In the present disclosure, the angle θ2 of the second semi-open sipes 19 is larger than the angle θ1 of the first semi-open sipes 18, and therefore the second semi-open sipes 19 can provide a large friction force in the tire axial direction, improving cornering performance on wet roads.

[0031] As a result of extensive research, the developers discovered that increasing the angle θ2 of the second semi-open sipes 19 tends to decrease wear resistance. They also found that providing inclined chamfered surfaces on both sides of the sipe edges of the second semi-open sipes 19 to improve wear resistance reduces friction on wet roads. For this reason, in the present disclosure, the first sipe wall 23 is provided with an inclined surface 23b that forms the chamfered portion 21, and the second sipe wall 24 is connected to the tread surface of the first crown land portion 11 without being chamfered. This allows for a balanced improvement in wear resistance and wet performance. In particular, the first sipe wall 23 is a sipe wall that is continuous with the groove wall of the crown circumferential groove 7 and forms an obtuse-angled corner in a tread plan view. Therefore, uneven wear around the sipe edges can be more effectively suppressed than when an inclined surface is provided on the second sipe wall 24. It is believed that this mechanism enables the present disclosure to exhibit excellent wear resistance and wet performance.

[0032] The following describes the configuration of this embodiment in more detail. Note that each configuration described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present disclosure can achieve the above-described effects even if it does not include the configurations described below. Furthermore, even if any one of the configurations described below is applied alone to a tire of the present disclosure having the above-described characteristics, performance improvement corresponding to each configuration can be expected. Furthermore, when several of the configurations described below are applied in combination, combined performance improvement corresponding to each configuration can be expected.

[0033] 3, the first full-open sipes 16 are inclined in a first direction with respect to the tire axial direction. The angle of the first full-open sipes 16 with respect to the tire axial direction is, for example, 5 to 15 degrees.

[0034] Fig. 5 shows a cross-sectional view taken along line BB in Fig. 2. As shown in Fig. 5, the first full-open sipe 16 is a chamfered sipe including a sipe main body 20a having a width extending in the tire radial direction of 1.5 mm or less and a chamfered portion 21a having a width greater than the width of the sipe main body 20a and opening to the tread surface of the first crown land portion 11. The chamfered portion 21a of the first full-open sipe 16 includes a pair of inclined surfaces 25 formed on the sipe edge on both sides of the first full-open sipe 16. The angle θ3 of the inclined surfaces 25 with respect to the tire normal is, for example, 55 to 80°, and preferably 65 to 75°. Such a first full-open sipe 16 can reliably improve wear resistance.

[0035] The sipe main body 20a extends in the tire radial direction with a constant width, and in a preferred embodiment, extends parallel to the tire radial direction. The width W2 of the sipe main body 20a is, for example, 0.2 to 1.2 mm, and preferably 0.4 to 0.8 mm. The sipe main body 20a may extend in the tire radial direction while oscillating.

[0036] As shown in FIG. 3 , the chamfered portion 21 a of the first full-open sipe 16 is disposed over the entire length of the first full-open sipe 16. The chamfered width of the chamfered portion 21 a of the first full-open sipe 16 increases from the position where the chamfered width is minimum toward both sides in the tire axial direction. In a preferred embodiment, the chamfered width of the first full-open sipe 16 changes continuously. When the first full-open sipe 16 comes into contact with a wet road surface, the first full-open sipe 16 can effectively guide a water film toward the circumferential groove 3, which helps improve wet performance. In this specification, the chamfered width refers to the opening width of the sipe provided with the chamfered portion on the tread surface of the tread portion 2, and corresponds to the sum of the width of the inclined surface and the width of the sipe main body 20 in a plan view of the tread.

[0037] The inclined surface 25 of the chamfered portion 21a of the first full-open sipe 16 includes a first inclined surface 26a that continues to one sipe wall of the sipe main body 20a and a second inclined surface 27a that continues to the other sipe wall of the sipe main body 20a. In this embodiment, at an end 16a of the chamfered portion 21a of the first full-open sipe 16 on the first tread edge T1 side, the width of the first inclined surface 26a is smaller than the width of the second inclined surface 27a. Furthermore, at an end 16b of the chamfered portion 21a of the first full-open sipe 16 on the tire equator C side, the width of the first inclined surface 26a is larger than the width of the second inclined surface 27a. In a more preferable embodiment, the width of the inclined surface at a location where the groove wall of the circumferential groove 3 and the sipe wall of the first full-open sipe 16 join to form an obtuse-angled corner is larger than the width of the inclined surface at a location where the groove wall and the sipe wall join to form an acute-angled corner. As a result, uneven wear at the end of the first full-open sipe 16 is suppressed.

[0038] The first full-open sipes 16 extend in the axial direction of the tire at a constant depth. The depth of the first full-open sipes 16 is preferably, for example, 60% to 80% of the depth of the circumferential grooves 3. This improves wet performance and noise performance in a well-balanced manner.

[0039] 2, the first semi-open sipes 18 desirably terminate closer to the first tread edge T1 than the axial center of the first crown land portion 11. The axial length L2 of the first semi-open sipes 18 is, for example, 30% to 45% of the axial width W3 of the first crown land portion 11. Such first semi-open sipes 18 are useful for improving steering stability on dry roads (hereinafter sometimes simply referred to as "steering stability") and wet performance in a well-balanced manner.

[0040] The angle θ1 (shown in FIG. 3 ) of the first semi-open sipes 18 relative to the tire axial direction is, for example, 5 to 15°, and more preferably 5 to 12°. The first semi-open sipes 18 extend, for example, with a constant width from the tread surface to the bottom of the first crown land portion 11. The depth of the first semi-open sipes 18 is desirably smaller than the depth of the first full-open sipes 16. The depth of the first semi-open sipes 18 is 20% or less of the maximum depth of the first full-open sipes 16, and specifically, is 0.5 to 1.5 mm. Such first semi-open sipes 18 can provide friction on wet road surfaces while maintaining wear resistance and steering stability.

[0041] The angle θ2 (shown in FIG. 3) of the second semi-open sipes 19 is, for example, 15 to 25°, and more preferably 20 to 25°. The length L3 of the second semi-open sipes 19 in the tire axial direction is desirably greater than the length L2 of the first semi-open sipes 18. Specifically, the length L3 of the second semi-open sipes 19 is 110% to 150% of the length L2 of the first semi-open sipes 18. Such second semi-open sipes 19 are useful for improving wet performance and wear resistance in a well-balanced manner.

[0042] 4, the angle θ4 of the inclined surface 23b of the chamfered portion 21c of the second semi-open sipe 19 with respect to the tire normal is, for example, 55 to 65°. In a more desirable embodiment, the angle θ4 of the inclined surface 23b of the second semi-open sipe 19 is preferably smaller than the angle θ3 (shown in FIG. 5) of the inclined surface 25 of the first full-open sipe 16.

[0043] 3, it is desirable that the chamfer width of the chamfered portion 21b of the second semi-open sipe 19 becomes smaller toward the discontinuous end 19a. The second semi-open sipe 19 including such a chamfered portion 21b can effectively guide a water film toward the crown circumferential groove 7 when the second semi-open sipe 19 comes into contact with a wet road surface.

[0044] As shown in FIG. 2, the second crown land portion 12 is provided with a plurality of second full-open sipes 17, a plurality of third semi-open sipes 31, and a plurality of crown shallow grooves 32.

[0045] The second full-open sipes 17 completely traverse the second crown land portion 12 in the tire axial direction. The second full-open sipes 17 are inclined, for example, in the first direction with respect to the tire axial direction. The angle of the second full-open sipes 17 with respect to the tire axial direction is, for example, 5 to 15 degrees.

[0046] The second full-open sipe 17 has substantially the same cross-sectional shape as the first full-open sipe 16 and includes a sipe body and a chamfered portion. The chamfered portion of the second full-open sipe 17 is disposed over the entire length of the second full-open sipe 17. The chamfered portion of the second full-open sipe 17 includes a pair of inclined surfaces formed on the sipe edges on both sides of the second full-open sipe 17. The chamfered portion of the second full-open sipe 17 extends in the axial direction of the tire with a constant chamfer width W4, for example. Such second full-open sipe 17 helps to provide excellent wet performance and wear resistance.

[0047] The third semi-open sipe 31 communicates with the crown circumferential groove 7 and has a discontinuous end 31a in the second crown land portion 12. The third semi-open sipe 31 can have the same configuration as the second semi-open sipe 19 described above, and therefore, a description thereof will be omitted here.

[0048] The crown shallow groove 32 extends, for example, from the second shoulder circumferential groove 6 and terminates within the second crown land portion 12. The crown shallow groove 32 terminates closer to the second tread edge T2 than the axial center of the second crown land portion 12. The axial length L4 of the crown shallow groove 32 is, for example, 40% to 50% of the axial width W5 of the first crown land portion 11. Such crown shallow groove 32 helps to improve wear resistance and wet performance in a well-balanced manner.

[0049] The crown shallow groove 32 is inclined in a first direction with respect to the tire axial direction, for example. The angle of the crown shallow groove 32 with respect to the tire axial direction is, for example, 5 to 15 degrees. In a more desirable embodiment, the difference in angle between the second full-open sipe 17 and the crown shallow groove 32 is 5 degrees or less. This further improves wear resistance.

[0050] Fig. 6 shows a cross section taken along line CC in Fig. 2. As shown in Fig. 6, the crown shallow groove 32 has a groove depth d1 of, for example, 0.5 to 1.5 mm. The crown shallow groove 32 has a groove width W6 of, for example, 1.5 to 2.5 mm. In a more desirable embodiment, the crown shallow groove 32 has a V-shaped cross section formed by two groove walls 32a that are inclined relative to the tire radial direction. The angle θ5 of the groove wall 32a relative to the tire normal is, for example, 35 to 55°. When cornering on a wet road, for example, the groove wall 32a comes into contact with the ground as the land portion deforms due to increased ground pressure, thereby improving wet performance.

[0051] Fig. 7 shows an enlarged view of the first shoulder land portion 13. As shown in Fig. 7, the first shoulder land portion 13 is provided with, for example, a plurality of first shoulder lateral grooves 35 and a plurality of shoulder sipes 36.

[0052] The first shoulder lateral grooves 35 extend axially inward from at least the first tread edge T1 and are discontinued within the first shoulder land portion 13. In this embodiment, the first shoulder lateral grooves 35 extend across the first tread edge T1. The axial distance L5 from the discontinued ends 35a of the first shoulder lateral grooves 35 to the first shoulder circumferential grooves 5 is, for example, 5% to 20% of the width W7 of the contact patch of the first shoulder land portion 13.

[0053] FIG. 8 shows a cross section taken along line DD in FIG. 7. As shown in FIG. 8, the first shoulder lateral groove 35 is provided with a chamfered portion 37. The chamfered portion 37 includes an inclined surface 38 between the tread surface of the first shoulder land portion 13 and the groove wall 35w of the first shoulder lateral groove 35. The angle θ6 of the inclined surface 38 with respect to the tire normal is, for example, 35 to 55°. The width W8 and depth d2 of the inclined surface 38 are preferably 0.2 to 0.7 mm, respectively. The first shoulder lateral groove 35 having such a chamfered portion 37 can exhibit excellent wear resistance.

[0054] As shown in Fig. 7, it is desirable that the width W8 (shown in Fig. 8) of the inclined surface 38 of the chamfered portion 37 of the first shoulder lateral groove 35 increases axially outward around the first tread edge T1. Specifically, at the first tread edge T1, the width W8 of the inclined surface 38 is 20% to 30% of the width of the region excluding the inclined surface 38 of the first shoulder lateral groove 35. Furthermore, at the axially outer end 35b of the first shoulder lateral groove 35, the width W8 of the inclined surface 38 is 45% to 55% of the width of the region excluding the inclined surface 38 of the first shoulder lateral groove 35. As a result, when a large load is applied to the tire during cornering, for example, the inclined surface 38 comes into contact with the ground, thereby providing a large grip.

[0055] The shoulder sipes 36 extend, for example, from the first shoulder circumferential groove 5 to a position beyond the first tread edge T1. The shoulder sipes 36 extend, for example, with a constant width from the tread surface to the bottom of the tread portion 2. The depth of the shoulder sipes 36 is, for example, 0.5 to 1.5 mm. In a more desirable embodiment, the shoulder sipes 36 and the above-mentioned first semi-open sipes 18 (shown in FIG. 2) are configured to have the same depth. Such shoulder sipes 36 can provide friction on wet roads while maintaining steering stability and wear resistance.

[0056] Fig. 9 shows an enlarged view of the second shoulder land portion 14. As shown in Fig. 9, the second shoulder land portion 14 is provided with, for example, a plurality of second shoulder lateral grooves 41 and a plurality of shoulder shallow grooves 42.

[0057] For example, the second shoulder lateral grooves 41 extend axially inward from at least the second tread edge T2 and terminate within the second shoulder land portion 14. In this embodiment, the second shoulder lateral grooves 41 extend across the second tread edge T2. The angle of the second shoulder lateral grooves 41 relative to the tire axial direction preferably increases axially inward. The axial distance L6 from the end 41a of the second shoulder lateral grooves 41 to the second shoulder circumferential groove 6 is 3% to 10% of the tread width W9 of the second shoulder land portion 14. In a more preferred embodiment, the distance L6 is shorter than the axial distance L5 (shown in FIG. 7 ) from the end 35a of the first shoulder lateral groove 35 to the first shoulder circumferential groove 5. This achieves a balanced improvement in wear resistance and wet performance, while also reducing pitch noise from the first shoulder lateral grooves 35 and second shoulder lateral grooves 41 to white noise, which is expected to improve noise performance.

[0058] The shoulder shallow groove 42 extends, for example, from the second shoulder circumferential groove 6 and terminates within the second shoulder land portion 14. In this embodiment, the shoulder shallow groove 42 extends, for example, further toward the second tread edge T2 than the terminated end 41a of the second shoulder lateral groove 41. The axial length L7 of the shoulder shallow groove 42 is preferably shorter than the axial length L4 (shown in FIG. 2 ) of the crown shallow groove 32. Specifically, the length L7 of the shoulder shallow groove 42 is 50% to 80% of the length L4 of the crown shallow groove 32. Such shoulder shallow grooves 42 are useful for improving wear resistance and wet performance in a well-balanced manner.

[0059] At the end of the shoulder shallow groove 42 on the side of the first shoulder circumferential groove 5, the shoulder shallow groove 42 has substantially the same cross-sectional shape as the above-described crown shallow groove 32. Therefore, the cross-sectional configuration of the above-described crown shallow groove 32 can be applied to the shoulder shallow groove 42. Furthermore, the width and depth of the shoulder shallow groove 42 become smaller toward the second tread edge T2. This improves wear resistance and steering stability.

[0060] In order to improve wet performance and wear resistance in a well-balanced manner, the land ratio of the tread portion 2 of this embodiment is preferably, for example, 60% to 70%, as shown in Figure 1. In this specification, the "land ratio" refers to the ratio Sb / Sa of the actual total contact area Sb to the total area Sa of the virtual contact area in which all grooves and sipes are filled.

[0061] Although a tire according to one embodiment of the present disclosure has been described in detail above, the present disclosure is not limited to the above-described specific embodiment and can be modified and implemented in various aspects. [Example]

[0062] Pneumatic tires of size 185 / 65R15 having the basic pattern shown in FIG. 1 were prototyped based on the specifications in Table 1. Each example in Table 1 has a common configuration of the first semi-open sipe, but the angle θ2 and length L3 of the second semi-open sipe are appropriately changed. A comparative example was also prototyped, having a first crown land portion a shown in FIG. 10. As shown in FIG. 10, in the first crown land portion a of the comparative example tire, the first semi-open sipe b and the second semi-open sipe c are arranged at the same angle relative to the tire axial direction, and the second semi-open sipe c does not have a chamfered portion. Except for the above-mentioned features, the comparative example tire is substantially the same as the example tire. These test tires were also tested for wet performance, wear resistance, and handling stability on dry roads. The common specifications and test methods for each test tire are as follows: Rim: 15 x 6.0J Tire pressure: 230kPa on all wheels Test vehicle: 1800cc, front-wheel drive Tire mounting position: All wheels

[0063] <Wet performance> The wet performance of the test vehicle when driven on a wet road surface was evaluated by the driver. The results are rated based on the wet performance of the comparative example being 100, with a higher score indicating better wet performance.

[0064] <Wear resistance> The test vehicle was driven a certain distance on a public road, and the remaining land height of the first crown land portion was measured. The results were expressed as an index, with the remaining land height of the comparative example being set at 100, and a larger value indicates better wear resistance. The test results are shown in Table 1.

[0065] [Table 1]

[0066] The sum of the evaluation scores for the wet performance and wear resistance in Table 1 may be used as an index of the overall performance of the tire. As shown in Table 1, the test results confirmed that the tires of the examples exhibited excellent wet performance and wear resistance.

[0067] [Note] The present disclosure includes the following aspects.

[0068] [Disclosure 1] A tire having a tread portion, The tread portion is composed of three circumferential grooves extending continuously in the tire circumferential direction between the first tread edge and the second tread edge, and four land portions divided by the three circumferential grooves, the three circumferential grooves include a first shoulder circumferential groove provided between the first tread edge and the tire equator, and a crown circumferential groove adjacent to the first shoulder circumferential groove on the tire equator side, the four land portions include a first crown land portion partitioned between the first shoulder circumferential groove and the crown circumferential groove, the first crown land portion is provided with at least one first full-open sipe that completely crosses the first crown land portion in the tire axial direction, at least one first semi-open sipe that communicates with the first shoulder circumferential groove and has an end that is interrupted within the first crown land portion, and at least one second semi-open sipe that communicates with the crown circumferential groove and has an end that is interrupted within the first crown land portion, the first semi-open sipe and the second semi-open sipe are inclined in a first direction with respect to the tire axial direction, an angle of the second semi-open sipe with respect to the tire axial direction is larger than an angle of the first semi-open sipe with respect to the tire axial direction, the second semi-open sipe is a chamfered sipe including a sipe main body portion having a width of 1.5 mm or less extending in the tire radial direction, and a chamfered portion having a width larger than the width of the sipe main body portion and opening to the tread surface of the first crown land portion, the second semi-open sipe includes a first sipe wall that is continuous with a groove wall of the crown circumferential groove and forms an obtuse-angled corner portion, and a second sipe wall that is opposite to the first sipe wall, The first sipe wall includes a main body surface that constitutes the sipe main body portion and an inclined surface that constitutes the chamfered portion, The second sipe wall is connected to the tread surface of the first crown land portion without being chamfered. tire. [Disclosure 2] The tread portion has a specified orientation for installation on a vehicle, The tire according to Disclosure 1, wherein the first tread edge is located on an inner side of the vehicle when mounted on the vehicle. [Disclosure 3] The tire according to Disclosure 1 or 2, wherein the land ratio of the tread portion is 60% to 70%. [Disclosure 4] The tire according to any one of Disclosures 1 to 3, wherein a chamfer width of the chamfered portion of the second semi-open sipe becomes smaller toward the discontinuous end. [Disclosure 5] The tire according to any one of Disclosures 1 to 4, wherein the first full-open sipe is a chamfered sipe including a sipe main body portion having a width extending in the tire radial direction of 1.5 mm or less, and a chamfered portion having a width greater than the width of the sipe main body portion and opening to the tread surface of the first crown land portion. [Disclosure 6] The tire described in the present disclosure 5, wherein the chamfered portion of the first full-open sipe includes a pair of inclined surfaces formed on sipe edges on both sides of the first full-open sipe. [Disclosure 7] The tire according to Disclosure 5 or 6, wherein the chamfered portion of the first full-open sipe has a chamfer width that increases from a position where the chamfer width is minimum toward both sides in the tire axial direction. [Disclosure 8] The tire according to any one of Disclosures 1 to 7, wherein the first semi-open sipe extends with a constant width from the tread surface to the bottom of the first crown land portion. [Disclosure 9] The tire according to any one of disclosures 1 to 8, wherein the axial length of the second semi-open sipe is greater than the axial length of the first semi-open sipe. [Disclosure 10] the four land portions include a second crown land portion adjacent to the first crown land portion, the second crown land portion is provided with at least one second full-open sipe that completely crosses the second crown land portion in the tire axial direction, The second full-open sipe is a chamfered sipe including a sipe main body portion having a width of 1.5 mm or less extending in the tire radial direction, and a chamfered portion having a width larger than the width of the sipe main body portion and opening to the tread surface of the second crown land portion, The tire according to any one of claims 1 to 9, wherein, in a plan view of the tread, the chamfered portion of the second full-open sipe extends in the tire axial direction with a constant chamfer width. [Explanation of symbols]

[0069] 2 Tread section 3 Circumferential groove 4 Land 5 First shoulder circumferential groove 7 Crown circumferential groove 11 Crown No. 1 Land Section 16 First full open sipe 18 No. 1 semi-open sipe 19 Second semi-open sipe 20 Sipe body 21 Chamfered part 23 First sipe wall 24 Second sipe wall 23a Body side 23b Slope T1 First tread edge T2 Second tread edge

Claims

1. A tire having a tread portion, the tread portion is composed of three circumferential grooves extending continuously in the tire circumferential direction between a first tread edge and a second tread edge, and four land portions divided by the three circumferential grooves, the three circumferential grooves include a first shoulder circumferential groove provided between the first tread edge and the tire equator, and a crown circumferential groove adjacent to the first shoulder circumferential groove on the tire equator side, the four land portions include a first crown land portion partitioned between the first shoulder circumferential groove and the crown circumferential groove, the first crown land portion is provided with at least one first full-open sipe that completely crosses the first crown land portion in the tire axial direction, at least one first semi-open sipe that communicates with the first shoulder circumferential groove and has an end that is interrupted within the first crown land portion, and at least one second semi-open sipe that communicates with the crown circumferential groove and has an end that is interrupted within the first crown land portion, the first semi-open sipe and the second semi-open sipe are inclined in a first direction with respect to the tire axial direction, an angle of the second semi-open sipe with respect to the tire axial direction is larger than an angle of the first semi-open sipe with respect to the tire axial direction, the second semi-open sipe is a chamfered sipe including a sipe main body portion having a width of 1.5 mm or less extending in the tire radial direction, and a chamfered portion having a width greater than the width of the sipe main body portion and opening to the tread surface of the first crown land portion, the second semi-open sipe includes a first sipe wall that is continuous with a groove wall of the crown circumferential groove and forms an obtuse-angled corner portion, and a second sipe wall that is opposite to the first sipe wall, The first sipe wall includes a main body surface that constitutes the sipe main body portion and an inclined surface that constitutes the chamfered portion, the second sipe wall is connected to the tread surface of the first crown land portion without being chamfered, The chamfer width of the chamfered portion of the second semi-open sipe becomes smaller toward the discontinuous end. tire.

2. The tread portion has a specified orientation for installation on a vehicle, The tire according to claim 1 , wherein the first tread edge is located on an inner side of the vehicle when mounted on the vehicle.

3. The tire according to claim 1 or 2, wherein a land ratio of the tread portion is 60% to 70%.

4. A tire described in any one of claims 1 to 3, wherein the first full-open sipe is a chamfered sipe including a sipe main body portion having a width extending in the tire radial direction of 1.5 mm or less, and a chamfered portion having a width greater than the width of the sipe main body portion and opening onto the tread surface of the first crown land portion.

5. A tire as described in claim 4, wherein the chamfered portion of the first full open sipe includes a pair of inclined surfaces formed on the sipe edges on both sides of the first full open sipe.

6. A tire as described in claim 4 or 5, wherein the chamfered portion of the first full-open sipe has a chamfer width that increases from the position where the chamfer width is smallest toward both sides in the tire axial direction.

7. A tire described in any one of claims 1 to 6, wherein the first semi-open sipe extends with a constant width from the tread surface to the bottom of the first crown land portion.

8. A tire described in any one of claims 1 to 7, wherein the axial length of the second semi-open sipe is greater than the axial length of the first semi-open sipe.

9. The four land portions include a second crown land portion adjacent to the first crown land portion, the second crown land portion is provided with at least one second full-open sipe that completely crosses the second crown land portion in the tire axial direction, The second full-open sipe is a chamfered sipe including a sipe main body portion having a width of 1.5 mm or less extending in the tire radial direction, and a chamfered portion having a width larger than the width of the sipe main body portion and opening to the tread surface of the second crown land portion, The tire according to claim 1 , wherein, in a plan view of the tread, the chamfered portion of the second full-open sipe extends in the tire axial direction with a constant chamfer width.

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