tire

Abstract

To provide a tire that can exert excellent on-snow performance, while maintaining steering stability on a dry road surface.SOLUTION: Each first crown sipe 41, each second crown sipe 42 and each third crown sipe 43 which are formed on a crown land part are opened on a tread surface 15s through chamfering surfaces 45. Each first crown sipe 41 and each third crown sipe 43 extend from a first vertical edge 15a and have terminating ends in the tread surface 15s. Each second crown sipe 42 extends from the second vertical edge 15b and has a terminating end in the tread surface 15s. A chamfer width of the chamfer parts 45 of each first crown sipe 41 and a chamfer width of the chamfer part 45 of each second crown sipe 42 are each constant in a sipe longitudinal direction. A chamfer width of the chamfer part 45 of each third crown sipe 43 become smaller continuously from the vertical edge toward the terminating end.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Patent Document 1 below proposes a tire with multiple crown sipes provided in the crown land portion. By improving the crown sipes, the tire achieves a good balance between steering stability on dry roads and performance on snow. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-008585 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, as vehicle performance has improved, there has been a demand for further improvements in handling stability on dry roads and performance on snow.

[0005] The present disclosure has been devised in view of the above-described circumstances, and has as its main object to provide a tire that can exhibit excellent performance on snow while maintaining steering stability on dry roads. [Means for solving the problem]

[0006] The present disclosure relates to a tire having a tread portion, the tread portion including a first tread edge, a second tread edge, and a crown land portion provided between the first tread edge and the second tread edge, the crown land portion including a first longitudinal edge extending in the tire circumferential direction on the first tread edge side, a second longitudinal edge extending in the tire circumferential direction on the second tread edge side, and a tread surface between the first longitudinal edge and the second longitudinal edge, the crown land portion being provided with a plurality of first crown sipes, a plurality of second crown sipes, and a plurality of third crown sipes, The crown sipes open at the tread surface via chamfered portions, and each of the first crown sipes and each of the third crown sipes extends from the first longitudinal edge and has an interrupted end within the tread surface, and each of the second crown sipes extends from the second longitudinal edge and has an interrupted end within the tread surface, and the chamfer width of the chamfered portion of each of the first crown sipes and the chamfer width of the chamfered portion of each of the second crown sipes are constant in the sipe longitudinal direction, and the chamfer width of the chamfered portion of each of the third crown sipes becomes continuously smaller from the first longitudinal edge toward the interrupted end. [Effects of the Invention]

[0007] By adopting the above-described configuration, the tire of the present disclosure can exhibit excellent performance on snow while maintaining steering stability on dry road surfaces. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a development view of a tread portion showing an embodiment of the present disclosure. FIG. [Figure 2] FIG. 2 is an enlarged view of the crown land portion of FIG. [Figure 3] 3 is an enlarged view of the first crown sipe, the second crown sipe, the third crown sipe, and the fourth crown sipe in FIG. 2. [Figure 4] FIG. 3 is a cross-sectional view taken along the line EE in FIG. 2. [Figure 5]FIG. 2 is an enlarged view of the first middle land portion of FIG. 1. [Figure 6] 6 is an enlarged view of the first middle lateral groove and the second middle lateral groove of FIG. 5. [Figure 7] FIG. 6 is a cross-sectional view taken along line AA in FIG. 5. [Figure 8] FIG. 6 is a cross-sectional view taken along line BB in FIG. 5. [Figure 9] FIG. 6 is a cross-sectional view taken along line CC in FIG. 5. [Figure 10] FIG. 6 is a cross-sectional view taken along line DD in FIG. 5. [Figure 11] FIG. 2 is an enlarged view of the second middle land portion of FIG. 1. [Figure 12] FIG. 12 is a cross-sectional view taken along the line FF in FIG. [Figure 13] FIG. 12 is a cross-sectional view taken along line GG in FIG. [Figure 14] FIG. 10 is an enlarged view of a second middle land portion according to another embodiment of the present disclosure. [Figure 15] FIG. 4 is an enlarged view of a 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, for example, a winter tire, and is suitably used as a pneumatic tire for passenger cars. However, the present disclosure is not limited to this 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 present disclosure includes a first tread edge T1, a second tread edge T2, a plurality of circumferential grooves 3 extending continuously in the tire circumferential direction between the first tread edge T1 and the second tread edge T2, and a plurality of land portions 4 separated by these circumferential grooves 3. As a desirable aspect, the tire 1 of the present embodiment is configured as a so-called five-rib tire in which the tread portion 2 is configured with four circumferential grooves 3 and five land portions 4.

[0011] The tread portion 2 of this embodiment has, for example, a specified orientation for mounting on a vehicle. As a result, the first tread edge T1 is intended to be located on the outer side of the vehicle when mounted on the vehicle. The second tread edge T2 is intended to be located on the inner side of the vehicle when mounted on the vehicle. The orientation for mounting on the vehicle is indicated, for example, by letters or symbols on the sidewall portion (not shown). However, the tire 1 of the present disclosure is not limited to this embodiment, and the orientation for mounting on a vehicle may not be specified.

[0012] 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°.

[0013] "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.

[0014] 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."

[0015] "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."

[0016] 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.

[0017] The circumferential grooves 3 include a first shoulder circumferential groove 5 and a second shoulder circumferential groove 6, and a first crown circumferential groove 7 and a second crown circumferential groove 8 provided between them. The first shoulder circumferential groove 5 is provided closest to the first tread edge T1 among the multiple circumferential grooves 3. The second shoulder circumferential groove 6 is provided closest to the second tread edge T2 among the multiple circumferential grooves 3. The first crown circumferential groove 7 is provided between the first shoulder circumferential groove 5 and the tire equator C. The second crown circumferential groove 8 is provided between the second shoulder circumferential groove 6 and 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, 25% to 35% of the tread width TW. The axial distance L2 from the tire equator C to the groove center line of the first crown circumferential groove 7 or the second crown circumferential groove 8 is preferably, for example, 5% to 15% 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] In this embodiment, the second shoulder circumferential groove 6, the first crown circumferential groove 7, and the second crown circumferential groove 8 extend linearly parallel to the tire circumferential direction. On the other hand, the first shoulder circumferential groove 5 has a groove edge on the tire equator C side that extends in a zigzag pattern. However, each circumferential groove 3 is not limited to this shape.

[0020] The groove width W1 of each circumferential groove 3 is preferably at least 3 mm or more. The groove width W1 of each circumferential groove 3 is preferably, for example, 3.0% to 7.0% of the tread width TW. The depth of each circumferential groove 3 is, for example, 5 to 10 mm in the case of a pneumatic tire for a passenger car.

[0021] The five land portions 4 of the present disclosure include a crown land portion 15 provided between the first tread edge T1 and the second tread edge T2. The crown land portion 15 of this embodiment is divided between the first crown circumferential groove 7 and the second crown circumferential groove 8. As a result, the crown land portion 15 is provided on the tire equator C. The land portions 4 of this embodiment also include a first middle land portion 13, a second middle land portion 14, a first shoulder land portion 11, and a second shoulder land portion 12. The first middle land portion 13 is divided between the first shoulder circumferential groove 5 and the first crown circumferential groove 7. The second middle land portion 14 is divided between the second shoulder circumferential groove 6 and the second crown circumferential groove 8. The first shoulder land portion 11 includes the first tread edge T1 and is divided axially outward of the first shoulder circumferential groove 5. The second shoulder land portion 12 includes the second tread edge T2 and is defined on the axially outer side of the second shoulder circumferential groove 6.

[0022] Fig. 2 shows an enlarged view of the crown land portion 15 of Fig. 1. As shown in Fig. 2, the crown land portion 15 includes a first longitudinal edge 15a extending in the tire circumferential direction on the side of the first tread edge T1, a second longitudinal edge 15b extending in the tire circumferential direction on the side of the second tread edge T2, and a tread surface 15s between the first longitudinal edge 15a and the second longitudinal edge 15b. The crown land portion 15 is also provided with a plurality of first crown sipes 41, a plurality of second crown sipes 42, and a plurality of third crown sipes 43. The crown land portion 15 of this embodiment is also provided with a plurality of fourth crown sipes 44.

[0023] 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.

[0024] 3 shows an enlarged view of the first crown sipes 41, the second crown sipes 42, the third crown sipes 43, and the fourth crown sipes 44. As shown in FIG. 3, in the present disclosure, the first crown sipes 41 extend from the first longitudinal edge 15a and have an interrupted end 41a within the tread surface 15s. The second crown sipes 42 extend from the second longitudinal edge 15b and have an interrupted end 42a within the tread surface 15s. The third crown sipes 43 extend from the first longitudinal edge 15a and have an interrupted end 43a within the tread surface 15s.

[0025] FIG. 4 shows a cross-sectional view taken along line EE in FIG. 2, illustrating the cross-sectional shape of the sipes. As shown in FIG. 4, the first crown sipe 41, the second crown sipe 42, and the third crown sipe 43 each open to the tread surface 15s via a chamfered portion 45. The chamfered portion 45 includes an inclined surface 45s cut out between the tread surface 15s and the sipe wall. In this embodiment, the inclined surface 45s is slightly curved so as to be convex outward in the tire radial direction. The inclined surface 45s may be flat, for example.

[0026] As shown in FIG. 2, the chamfer width W6 of the chamfered portion 45 of each first crown sipe 41 and the chamfer width W7 of the chamfered portion 45 of each second crown sipe 42 are constant in the sipe longitudinal direction. Meanwhile, the chamfer width of the chamfered portion 45 of each third crown sipe 43 continuously decreases from the first longitudinal edge 15a toward the discontinuous end 43a. By adopting the above-described configuration, the tire of the present disclosure can exhibit excellent on-snow performance while maintaining steering stability on dry roads (hereinafter sometimes simply referred to as "steering stability"). The mechanism behind this is as follows.

[0027] In the present disclosure, multiple crown sipes with discontinuous ends are provided in the crown land portion 15. Such sipes can improve on-snow performance while maintaining the rigidity of the crown land portion 15. Furthermore, because these sipes are open via the chamfered portions 45, the chamfered portions 45 can equalize the ground pressure acting on each portion of the crown land portion 15, which is expected to improve steering stability and on-snow performance.

[0028] Furthermore, the chamfer width of the third crown sipes 43 becomes smaller toward the end, thereby ensuring a sufficient contact area in the center of the crown land portion 15 and reliably maintaining steering stability. Due to this mechanism, the tire 1 of the present disclosure can exhibit excellent wet performance while maintaining steering stability.

[0029] 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.

[0030] Each of the first crown sipes 41 and each of the second crown sipes 42 are inclined in the same direction relative to the tire axial direction, and the angle of these sipes relative to the tire axial direction is, for example, 25 to 35 degrees.

[0031] The chamfer width W7 of the chamfered portion 45 of the second crown sipe 42 is 80% to 120% of the chamfer width W6 of the chamfered portion 45 of the first crown sipe 41, and in this embodiment, these are substantially the same, thereby suppressing uneven wear around these sipes.

[0032] The maximum chamfer width W8 of the chamfered portion 45 of the third crown sipe 43 is smaller than the chamfer width W6 of the chamfered portion 45 of the first crown sipe 41. Specifically, the chamfer width W8 of the third crown sipe 43 is 75% to 90% of the chamfer width W6 of the first crown sipe 41. In the third crown sipe 43 of this embodiment, the chamfered portion is substantially eliminated at the discontinuous end 43a, but this is not limited to this, and the chamfered portion 45 may remain at the discontinuous end 43a. The same applies to the fourth crown sipe 44 described below.

[0033] The fourth crown sipe 44 extends from the second longitudinal edge 15b and has a discontinuous end 44a within the tread surface 15s. In this embodiment, the fourth crown sipe 44 also opens at the tread surface 15s via a chamfered portion 45. It is desirable that the chamfer width of the chamfered portion 45 of the fourth crown sipe 44 continuously decreases from the second longitudinal edge 15b toward the discontinuous end 44a. This ensures a sufficient contact area in the center of the crown land portion 15, thereby reliably maintaining steering stability.

[0034] The maximum chamfer width W9 of the chamfered portion 45 of the fourth crown sipes 44 is smaller than the chamfer width W7 of the chamfered portion 45 of the second crown sipes 42. Specifically, the chamfer width W9 of the fourth crown sipes 44 is 75% to 90% of the chamfer width W7 of the second crown sipes 42. Such third crown sipes 43 and fourth crown sipes 44 are useful for improving steering stability and on-snow performance in a well-balanced manner.

[0035] 3, in this embodiment, the distance L4 in the tire circumferential direction between the outer end 41b of the first crown sipe 41 on the first longitudinal edge 15a side and the outer end 42b of the second crown sipe 42 on the second longitudinal edge 15b side is preferably 10% or less of the tire circumferential pitch length P1 (shown in FIG. 2) of the first crown sipe 41. As a result, when driving on wet roads, water displaced by the center of the land portion is more likely to be guided toward the outer ends of these sipes, improving wet performance.

[0036] The axial length L6 of the first crown sipe 41 is, for example, 40% to 60% of the axial width W5 (shown in FIG. 2, and the same applies hereinafter) of the tread surface 15s of the crown land portion 15. In this specification, the length of a sipe is measured at the center line of the sipe.

[0037] The second crown sipes 42 preferably cross the axial center of the tread surface 15s of the crown land portion 15. The discontinued ends 42a of the second crown sipes 42 are located closer to the first longitudinal edge 15a than the discontinued ends 41a of the first crown sipes 41. The axial length L7 of the second crown sipes 42 is preferably longer than the axial length L6 of the first crown sipes 41. Specifically, the length L7 of the second crown sipes 42 is 65% to 85% of the width W5 of the tread surface 15s of the crown land portion 15. Such second crown sipes 42 can improve on-snow and wet performance while maintaining steering stability.

[0038] The third crown sipes 43 and the fourth crown sipes 44 are inclined in the same direction as the first crown sipes 41 and the second crown sipes 42 with respect to the tire axial direction, and the angle of these sipes with respect to the tire axial direction is, for example, 25 to 35 degrees.

[0039] The distance L5 in the tire circumferential direction between the outer end 43b of the third crown sipe 43 on the first longitudinal edge 15a side and the outer end 44b of the fourth crown sipe 44 on the second longitudinal edge 15b side is preferably 10% or less of the tire circumferential pitch length P2 (shown in FIG. 2) of the third crown sipe 43. This further improves wet performance.

[0040] The axial length L8 of the third crown sipes 43 is shorter than the length L7 of the second crown sipes 42 and shorter than the length L6 of the first crown sipes 41. Furthermore, the discontinued ends 43a of the third crown sipes 43 are located closer to the first longitudinal edge 15a than the discontinued ends 44a of the fourth crown sipes 44. In a more preferred embodiment, the discontinued ends 43a of the third crown sipes 43 are located closer to the second longitudinal edge 15b than the discontinued ends 42a of the second crown sipes 42. The length L8 of the third crown sipes 43 is 25% to 45% of the width W5 of the tread surface 15s of the crown land portion 15. Such third crown sipes 43 are useful for achieving a good balance between steering stability and on-snow and wet performance.

[0041] From the same viewpoint, the axial length L9 of the fourth crown sipes 44 is, for example, shorter than the length L7 of the second crown sipes 42 and shorter than the length L6 of the first crown sipes 41. Specifically, the length L9 of the fourth crown sipes 44 is 25% to 45% of the width W5 of the tread surface 15s of the crown land portion 15.

[0042] Fig. 5 shows an enlarged view of the first middle land portion 13. As shown in Fig. 5, the first middle land portion 13 includes a first longitudinal edge 13a extending in the tire circumferential direction on the first tread edge T1 side, a second longitudinal edge 13b extending in the tire circumferential direction on the second tread edge T2 side, and a tread surface 13s between the first longitudinal edge 13a and the second longitudinal edge 13b. The first middle land portion 13 also has a plurality of middle lateral grooves 20. The middle lateral grooves 20 are inclined, for example, in the same direction as the first crown sipes 41 (shown in Fig. 2) with respect to the tire axial direction.

[0043] Figure 6 shows an enlarged view of two middle lateral grooves 20. Note that Figure 6 is an enlarged view of a first middle lateral groove 21 and a second middle lateral groove 22, which will be described later. As shown in Figure 6, at least one of the middle lateral grooves 20 includes a first groove portion 26 and a second groove portion 27. The first groove portion 26 extends axially from the first longitudinal edge 13a. The second groove portion 27 extends axially from the second longitudinal edge 13b.

[0044] In this embodiment, the first groove portion 26 and the second groove portion 27 are misaligned in the tire circumferential direction, forming a longitudinal groove edge 28e extending in the tire circumferential direction between the groove edge 26e of the first groove portion 26 and the groove edge 27e of the second groove portion 27. The maximum depth of the first groove portion 26 is different from the maximum depth of the second groove portion 27. When driving on snow, the middle lateral grooves 20 provide a large reaction force by strongly compacting and shearing the snow therein (hereinafter, such a reaction force may be referred to as a "snow column shear force"). Because the first groove portion 26 and the second groove portion 27 have different maximum depths, the groove portion with the smaller depth maintains the rigidity of the first middle land portion 13 and maintains steering stability, while the groove portion with the larger depth can provide a large snow column shear force, improving on-snow performance.

[0045] The longitudinal groove edges 28e provide axial friction and help improve cornering performance on snow. Furthermore, the combination of the longitudinal groove edges 28e with the first and second grooves 26 and 27 makes it easier for snow that has entered the deeper groove to be compacted more strongly in the axial direction, generating greater snow column shear force.

[0046] As shown in Figures 5 and 6, in this embodiment, each middle lateral groove 20 has the above-mentioned characteristics. In a plan view of the tread, the first groove portion 26 and the second groove portion 27 extend in the tire axial direction with a constant groove width W3 (shown in Figure 5). The groove width W3 of the first groove portion 26 and the second groove portion 27 is, for example, 15% to 25% of the width W2 (shown in Figure 5) of the contact patch of the first middle land portion 13. The angle of the first groove portion 26 and the second groove portion 27 with respect to the tire axial direction is, for example, 25 to 35 degrees.

[0047] The middle lateral grooves 20 include a plurality of first middle lateral grooves 21 and a plurality of second middle lateral grooves 22 having different depth distributions. The first middle lateral grooves 21 and the second middle lateral grooves 22 are, for example, arranged alternately in the tire circumferential direction.

[0048] Fig. 7 shows a cross-sectional view taken along line AA in Fig. 5. Fig. 7 is a cross-sectional view taken along line BB in Fig. 2. Fig. 5 is a cross-sectional view taken along line BB in Fig. 2. As shown in Figs. 7 and 8, the first groove portion 26 and the second groove portion 27 of the first middle axial groove 21 and the first groove portion 26 and the second groove portion 27 of the second middle axial groove 22 in this embodiment each extend in the groove longitudinal direction at a constant depth.

[0049] As shown in FIG. 7 , in the first middle lateral grooves 21, the maximum depth d1 of the first groove portions 26 is smaller than the maximum depth d2 of the second groove portions 27. In the first middle lateral grooves 21, the depth d2 of the second groove portions 27 is, for example, 60% to 80% of the depth dc of the first crown circumferential groove 7. Also, in the first middle lateral grooves 21, the depth d1 of the first groove portions 26 is 40% to 60% of the depth dc of the first crown circumferential groove 7. Thus, it is desirable that the depth d1 of the first groove portions 26 be 60% to 70% of the depth d2 of the second groove portions 27.

[0050] As shown in FIG. 8 , the second middle lateral grooves 22 have substantially the inverted shape of the first middle lateral grooves 21. That is, in the second middle lateral grooves 22, the maximum depth d1 of the first groove portions 26 is greater than the maximum depth d2 of the second groove portions 27. In the second middle lateral grooves 22, the depth d1 of the first groove portions 26 is, for example, 60% to 80% of the depth dc of the first crown circumferential groove 7. Also, in the second middle lateral grooves 22, the depth d2 of the second groove portions 27 is 40% to 60% of the depth dc of the first crown circumferential groove 7. Therefore, it is desirable that the depth d2 of the second groove portions 27 be 60% to 70% of the depth d1 of the first groove portions 26.

[0051] In this embodiment, the first middle lateral grooves 21 and the second middle lateral grooves 22 are alternately provided in the circumferential direction of the tire, thereby improving steering stability and performance on snow in a well-balanced manner.

[0052] Fig. 9 shows a cross-sectional view taken along line CC in Fig. 5. Fig. 9 is a cross-sectional view of the second groove portion 27 of the first middle lateral groove 21 or the first groove portion 26 of the second middle lateral groove 22 (hereinafter, these may be collectively referred to as deep groove portion 37). Fig. 10 shows a cross-sectional view taken along line DD in Fig. 5. Fig. 10 is a cross-sectional view of the first groove portion 26 of the first middle lateral groove 21 or the second groove portion 27 of the second middle lateral groove 22 (hereinafter, these may be collectively referred to as shallow groove portion 36).

[0053] As shown in Figures 9 and 10, the deep groove portion 37 and the shallow groove portion 36 each preferably open via a chamfered portion 25. The chamfered portion 25 includes an inclined surface 25s cut out between the tread surface of the land portion and the groove wall. In this embodiment, the inclined surface 25s is slightly curved so as to be convex outward in the tire radial direction. The inclined surface 25s may be flat, for example. Such a chamfered portion 25 helps to equalize the ground pressure acting on the tread surface 13s and improve uneven wear resistance.

[0054] As shown in FIG. 9 , the deep groove portion 37 includes, for example, a flat groove bottom 37d. On the other hand, as shown in FIG. 10 , the shallow groove portion 36 is connected to groove bottom sipes 38 that open at the groove bottom 36d and extend radially. These groove bottom sipes 38 facilitate the shallow groove portion 36 to open appropriately, thereby improving on-snow performance. Note that the depth d1 of the first groove portion 26 of the first middle lateral groove 21 and the depth d2 of the second groove portion 27 of the second middle lateral groove 22 do not include the groove bottom sipes 38. Also, the groove bottom sipes 38 are omitted in FIGS. 7 and 8 . In a preferred embodiment, the total depth from the tread surface of the land portion to the bottom of the groove bottom sipes 38 is also smaller than the depth of the deep groove portion 37. This improves steering stability and on-snow performance in a well-balanced manner.

[0055] As shown in FIG. 6, in this embodiment, each of the groove edges on both sides of one middle lateral groove 20 includes a longitudinal groove edge 28e. These two longitudinal groove edges 28e are located, for example, in the central region when the tread surface 13s of the first middle land portion 13 is divided into thirds in the axial direction. As a result, the two longitudinal groove edges 28e are located on either side of the axial center position of the tread surface 13s of the first middle land portion 13. The two longitudinal groove edges 28e each extend along the tire circumferential direction and, in a preferred embodiment, extend parallel to each other. The angle of the longitudinal groove edges 28e relative to the tire circumferential direction is, for example, 10° or less, preferably 5° or less. The length L3 of the longitudinal groove edge 28e in the tire circumferential direction is preferably smaller than the maximum groove width of the first groove portion 26 and the second groove portion 27. Specifically, the length L3 is 75% to 95% of the groove width. Such longitudinal groove edges 28e can suppress uneven wear and improve cornering performance when traveling on snow.

[0056] The middle lateral groove 20 includes a longitudinal groove portion 28 provided between the first groove portion 26 and the second groove portion 27. In this embodiment, for example, the region between one longitudinal groove edge 28e and an imaginary extension line extending in the length direction thereof and the other longitudinal groove edge 28e and an imaginary extension line extending in the length direction thereof is configured as the longitudinal groove portion 28.

[0057] 7 and 8, the maximum depth d3 of the longitudinal groove portion 28 is smaller than the maximum depth d1 of the first groove portion 26 and the maximum depth d2 of the second groove portion 27. Specifically, the maximum depth d3 of the longitudinal groove portion 28 is 20% to 30% of the depth dc of the first crown circumferential groove 7. Such a longitudinal groove portion 28 increases the rigidity of the central portion of the first middle land portion 13 and improves uneven wear resistance.

[0058] As shown in Fig. 5, it is desirable that the first middle land portion 13 be provided with at least one longitudinal sipe 30 extending in the tire circumferential direction. In this embodiment, the first middle land portion 13 has a plurality of longitudinal sipes 30 spaced apart in the tire circumferential direction. Furthermore, the longitudinal sipe 30 in this embodiment extends with a constant width from the tread surface 13s to the bottom of the first middle land portion 13. Such a longitudinal sipe 30 can provide a large friction force in the tire axial direction when driving on wet or snowy roads.

[0059] The longitudinal sipes 30 are preferably arranged in the central region when the tread surface 13s of the first middle land portion 13 is divided into three equal parts in the axial direction of the tire. The angle of the longitudinal sipes 30 relative to the circumferential direction of the tire is, for example, 10° or less, and preferably 5° or less. Such longitudinal sipes 30 can provide a large axial friction force when driving on snow.

[0060] The longitudinal sipes 30, for example, cross the middle lateral grooves 20 in the tire circumferential direction. In a preferred embodiment, the longitudinal sipes 30 are arranged to cross the first middle lateral grooves 21, and do not communicate with the second middle lateral grooves 22. More specifically, the longitudinal sipes 30 cross the longitudinal groove portions 28 of the first middle lateral grooves 21. As a result, the longitudinal sipes 30 are configured as groove bottom sipes at the groove bottoms of the longitudinal groove portions 28. On the other hand, the second middle lateral grooves 22 do not have such a configuration. This improves the steering stability, snow performance, and uneven wear resistance in a balanced manner.

[0061] As shown in FIG. 5 , the first middle land portion 13 is provided with a plurality of first middle sipes 31 and a plurality of second middle sipes 32. The first middle sipes 31 extend from the first longitudinal edge 13a and communicate with the longitudinal sipes 30. The second middle sipes 32 extend from the second longitudinal edge 13b and communicate with the longitudinal sipes 30. In a preferred embodiment, the ends of the first middle sipes 31 within the tread surface 13s communicate with the ends of the longitudinal sipes 30 on one side in the tire circumferential direction. The ends of the second middle sipes 32 within the tread surface 13s communicate with the ends of the longitudinal sipes 30 on the other side in the tire circumferential direction. These first middle sipes 31 and second middle sipes 32 cooperate with the longitudinal sipes 30 to provide friction in multiple directions, further improving on-snow performance.

[0062] The first middle sipes 31 and the second middle sipes 32 are inclined, for example, in the same direction as the middle lateral grooves 20 relative to the tire axial direction. The angle of these sipes relative to the tire axial direction is, for example, 25 to 35 degrees. In a preferred embodiment, the first middle sipes 31 and the longitudinal sipes 30 are connected to each other so that the corners therebetween form acute angles. Similarly, the second middle sipes 32 and the longitudinal sipes 30 are connected to each other so that the corners therebetween form acute angles. This allows the corners to more easily dig into the road surface when driving on snow, resulting in excellent on-snow performance.

[0063] The first middle sipes 31 and the second middle sipes 32 each open to the tread surface 13s via a chamfered portion 35. The chamfered portions 35 of these sipes can have the same configuration as the chamfered portions 45 of the crown sipes (shown in FIG. 4), and a description thereof will be omitted here. Such chamfered portions 35 help to equalize the ground pressure acting on the tread surface 13s, improving steering stability and uneven wear resistance.

[0064] As shown in Figure 5, the chamfered portion 35 of the first middle sipe 31 desirably has a chamfer width that decreases toward the longitudinal sipe 30 side. Similarly, the chamfered portion 35 of the second middle sipe 32 desirably has a chamfer width that decreases toward the longitudinal sipe 30 side. This ensures a sufficient contact area in the center of the first middle land portion 13, thereby maintaining steering stability. The chamfered width is the opening width of the chamfered portion in a plan view of the tread. The opening width also refers to the width in a direction perpendicular to the sipe longitudinal direction.

[0065] FIG. 11 shows an enlarged view of the second middle land portion 14. As shown in FIG. 11, the second middle land portion 14 is provided with third middle lateral grooves 23 and fourth middle lateral grooves 24 alternately arranged in the tire circumferential direction. The third middle lateral grooves 23 and fourth middle lateral grooves 24 have the same shape in a tread plan view and completely cross the second middle land portion 14 in the tire axial direction. The third middle lateral grooves 23 and fourth middle lateral grooves 24 are inclined in the same direction relative to the tire axial direction as the middle lateral grooves 20 (shown in FIG. 2). The angles of the third middle lateral grooves 23 and fourth middle lateral grooves 24 relative to the tire axial direction are smaller than the angles of the middle lateral grooves 20 (shown in FIG. 2) relative to the tire axial direction and are smaller than the angles of each sipe provided in the crown land portion 15 (shown in FIG. 9) relative to the tire axial direction. Specifically, the angles of the third middle lateral grooves 23 and fourth middle lateral grooves 24 relative to the tire axial direction are, for example, 10 to 20 degrees. On the other hand, the third middle lateral groove 23 and the fourth middle lateral groove 24 have different internal configurations.

[0066] Fig. 12 shows a cross section taken along line FF in Fig. 11. As shown in Fig. 12, the third middle lateral grooves 23 have shallow groove portions 46 on the second crown circumferential groove 8 side and deep groove portions 47 on the second shoulder circumferential groove 6 side. Fig. 13 shows a cross section taken along line GG in Fig. 11. As shown in Fig. 13, the fourth middle lateral grooves 24 have a shape that is essentially the inverted shape of the third middle lateral grooves 23. That is, the fourth middle lateral grooves 24 have deep groove portions 47 on the second crown circumferential groove 8 side and shallow groove portions 46 on the second shoulder circumferential groove 6 side. In this embodiment, the third middle lateral grooves 23 and the fourth middle lateral grooves 24 are alternately arranged in the tire circumferential direction, thereby improving uneven wear resistance and handling stability.

[0067] The shallow groove portions 46 of the third middle lateral grooves 23 and the fourth middle lateral grooves 24 may have the same configuration as the shallow groove portions 36 of the middle lateral grooves 20 (shown in FIG. 10). Similarly, the deep groove portions 47 of the third middle lateral grooves 23 and the fourth middle lateral grooves 24 may have the same configuration as the deep groove portions 37 of the middle lateral grooves 20 (shown in FIG. 9).

[0068] As shown in FIG. 11 , the second middle land portion 14 is provided with a plurality of middle sipe groups 55 in the tire circumferential direction, each group including a plurality of axially aligned bent sipes 56. In this embodiment, the bent sipes 56 are arranged so as to overlap in the tire axial direction, thereby forming the middle sipe group 55. The bent sipes 56 include a portion that protrudes toward one or the other circumferential side of the tire. Such middle sipe groups 55 are difficult to open during braking and driving, making it difficult for snow and ice to become clogged inside when driving on snow, thereby enabling the tire to continuously demonstrate excellent snow performance.

[0069] The present disclosure is not limited to the second middle land portion 14 shown in FIG. 11 . FIG. 14 shows an enlarged view of a second middle land portion 14 according to another embodiment of the present disclosure. As shown in FIG. 14 , the second middle land portion 14 of this embodiment includes, in addition to the third middle lateral grooves 23 and fourth middle lateral grooves 24, a plurality of third middle sipes 33 and a plurality of fourth middle sipes 34. The third middle sipes 33 extend from the second crown circumferential groove 8 and terminate within the tread surface of the second middle land portion 14. The fourth middle sipes 34 extend from the second shoulder circumferential groove 6 and terminate within the tread surface. The third middle sipes 33 and fourth middle sipes 34 are inclined, for example, in the same direction as the third middle lateral grooves 23 and fourth middle lateral grooves 24 with respect to the tire axial direction. The angle of these sipes with respect to the tire axial direction is, for example, 10 to 20 degrees. The third middle sipes 33 and the fourth middle sipes 34 can have the same configuration as the first middle sipes 31 or the second middle sipes 32 described above.

[0070] In yet another embodiment, the second middle land portion 14 may have the above-described middle sipe group 55 (shown in FIG. 11) and the third middle sipes 33 and fourth middle sipes 34 (not shown) shown in FIG. 14 arranged between the third middle lateral groove 23 and the fourth middle lateral groove 24 that are adjacent in the tire circumferential direction. Such a sipe arrangement helps to further improve on-snow performance.

[0071] As shown in FIG. 1 , the first shoulder land portion 11 is provided with a plurality of first shoulder lateral grooves 51 and first shoulder sipes 52. The first shoulder lateral grooves 51 and first shoulder sipes 52 extend, for example, from the first shoulder circumferential groove 5 to at least the first tread edge T1. The second shoulder land portion 12 is provided with a shoulder sipe group 60, which includes a plurality of second shoulder lateral grooves 53 and a plurality of bent sipes 61 aligned in the axial direction of the tire. The shoulder sipe group 60 has substantially the same configuration as the above-mentioned middle sipe group 55. These lateral grooves and sipes help to further improve on-snow performance.

[0072] 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]

[0073] As an example, a pneumatic tire of size 245 / 40ZR18 having the basic pattern of Fig. 1 was prototyped. As a comparative example, a tire having a crown land portion a shown in Fig. 15 was prototyped. The crown land portion a was provided with third crown sipes b and fourth crown sipes c, each extending with a constant chamfer width. The comparative example tire had substantially the same configuration as the example tire, except for the above-mentioned points.

[0074] The comparative example and the example were tested for steering stability on dry roads and performance on snow. The common specifications and test methods for each test tire are as follows: Rim: 18 x 8.5J Tire pressure: 240kPa on all wheels Test vehicle: 2000cc, rear-wheel drive Tire mounting position: All wheels

[0075] <Steering stability on dry roads> The driving stability of the test vehicle when it was driven on a dry road surface was evaluated by the driver. The results are expressed as a score, with the driving stability of the comparative example being 100, and the higher the score, the better the driving stability.

[0076] <Snow performance> The test vehicle was driven on snowy roads and its snow performance was evaluated by the driver. The results were scored based on the snow performance of the comparative example being 100, with a higher score indicating better snow performance. The test results are shown in Table 1.

[0077] [Table 1]

[0078] As a result of the test, it was confirmed that the tire of the example exhibited excellent performance on snow while maintaining steering stability on dry roads.

[0079] [Note] The present disclosure includes the following aspects.

[0080] [Disclosure 1] A tire having a tread portion, the tread portion includes a first tread edge, a second tread edge, and a crown land portion provided between the first tread edge and the second tread edge, the crown land portion includes a first longitudinal edge extending in the tire circumferential direction on the first tread end side, a second longitudinal edge extending in the tire circumferential direction on the second tread end side, and a tread surface between the first longitudinal edge and the second longitudinal edge, The crown land portion is provided with a plurality of first crown sipes, a plurality of second crown sipes, and a plurality of third crown sipes, Each of the first crown sipes, each of the second crown sipes, and each of the third crown sipes opens at the tread surface via a chamfered portion, Each of the first crown sipes and each of the third crown sipes extends from the first longitudinal edge and has an interrupted end within the tread surface, Each of the second crown sipes extends from the second longitudinal edge and has an interrupted end within the tread surface, a chamfer width of the chamfered portion of each of the first crown sipes and a chamfer width of the chamfered portion of each of the second crown sipes are constant in a sipe longitudinal direction, The chamfer width of the chamfered portion of each third crown sipe continuously decreases from the first vertical edge toward the discontinuous end. tire. [Disclosure 2] The tire described in Disclosure 1, wherein each of the first crown sipes, each of the second crown sipes, and each of the third crown sipes are inclined in the same direction relative to the tire axial direction. [Disclosure 3] The tire according to Disclosure 1 or 2, wherein the chamfer width of the chamfered portion of the second crown sipe is 80% to 120% of the chamfer width of the chamfered portion of the first crown sipe. [Disclosure 4] The tire according to any one of Disclosures 1 to 3, wherein the maximum chamfer width of the chamfered portion of the third crown sipe is smaller than the chamfer width of the chamfered portion of the first crown sipe. [Disclosure 5] The tire according to any one of Disclosures 1 to 4, wherein the axial length of the third crown sipes is smaller than the axial length of the first crown sipes. [Disclosure 6] The tire according to any one of disclosures 1 to 5, wherein the interrupted end of the third crown sipe is located closer to the second longitudinal edge than the interrupted end of the second crown sipe. [Disclosure 7] The crown land portion is provided with a plurality of fourth crown sipes extending from the second vertical edge and having interrupted ends within the tread surface, Each of the fourth crown sipes is open at the tread surface through a chamfered portion, The tire according to any one of Disclosures 1 to 6, wherein the chamfer width of the chamfered portion of the fourth crown sipe continuously decreases from the second vertical edge toward the discontinuous end. [Disclosure 8] The tire described in Disclosure 7, wherein the maximum chamfer width of the chamfered portion of the fourth crown sipe is smaller than the chamfer width of the chamfered portion of the second crown sipe. [Disclosure 9] The tire according to Disclosure 7 or 8, wherein the axial length of the fourth crown sipe is smaller than the axial length of the second crown sipe. [Disclosure 10] The tread portion has a specified orientation for installation on a vehicle, The tire according to any one of Disclosures 1 to 9, wherein the first tread edge is located on an outer side of the vehicle when mounted on the vehicle. [Explanation of symbols]

[0081] 2 Tread section 15 Crown Land Division 15a First vertical edge 15b Second vertical edge 15s tread 41 First crown sipe 42 Second crown sipe 43 3rd crown sipe 45 Chamfered part T1 First tread edge T2 Second tread edge

Claims

1. A tire having a tread portion, the tread portion includes a first tread edge, a second tread edge, and a crown land portion provided between the first tread edge and the second tread edge, the crown land portion includes a first longitudinal edge extending in the tire circumferential direction on the first tread end side, a second longitudinal edge extending in the tire circumferential direction on the second tread end side, and a tread surface between the first longitudinal edge and the second longitudinal edge, a plurality of first crown sipes, a plurality of second crown sipes, and a plurality of third crown sipes are provided in the crown land portion, Each of the first crown sipes, each of the second crown sipes, and each of the third crown sipes opens at the tread surface via a chamfered portion, Each of the first crown sipes and each of the third crown sipes extends from the first longitudinal edge and has an interrupted end within the tread surface, Each of the second crown sipes extends from the second longitudinal edge and has an interrupted end within the tread surface, a chamfer width of the chamfered portion of each of the first crown sipes and a chamfer width of the chamfered portion of each of the second crown sipes are constant in a sipe longitudinal direction, a chamfer width of the chamfered portion of each of the third crown sipes continuously decreasing from the first vertical edge toward the discontinuous end; tire.

2. The tire according to claim 1 , wherein the first crown sipes, the second crown sipes, and the third crown sipes are inclined in the same direction relative to the tire axial direction.

3. 3. The tire according to claim 1, wherein the chamfer width of the chamfered portion of the second crown sipe is 80% to 120% of the chamfer width of the chamfered portion of the first crown sipe.

4. The tire according to claim 1 , wherein a maximum chamfer width of the chamfered portion of the third crown sipe is smaller than a maximum chamfer width of the chamfered portion of the first crown sipe.

5. The tire according to claim 1 , wherein the axial length of the third crown sipe is smaller than the axial length of the first crown sipe.

6. The tire according to claim 1 , wherein the interrupted end of the third crown sipe is located closer to the second longitudinal edge than the interrupted end of the second crown sipe.

7. a plurality of fourth crown sipes extending from the second vertical edge and having interrupted ends within the tread surface are provided in the crown land portion; Each of the fourth crown sipes is open at the tread surface via a chamfered portion, The tire according to claim 1 , wherein a chamfer width of the chamfered portion of the fourth crown sipe continuously decreases from the second vertical edge toward the discontinuous end.

8. The tire according to claim 7 , wherein a maximum chamfer width of the chamfered portion of the fourth crown sipe is smaller than a maximum chamfer width of the chamfered portion of the second crown sipe.

9. The tire according to claim 7 or 8, wherein the axial length of the fourth crown sipe is smaller than the axial length of the second crown sipe.

10. 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 outer side of the vehicle when mounted on the vehicle.

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