tire

Abstract

To provide a 5 rib tire that can improve steering stability and noise performance.SOLUTION: A tread part 2 includes four circumferential grooves 3 and five land parts 4. Two tread ends are ends of a contact area at the time of 50% loading. In each of the five land parts 4 is not formed a groove whose groove width is more than 2.0 mm but is formed only a sipe 9. The five land parts 4 include shoulder land parts 11. In the shoulder land parts 11 are formed a plurality of shoulder sipes 20. At least one of the shoulder sipes 20 includes an inclined part 21 and an axial-directional part 22. The axial directional part 22 crosses the tread ends.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, various tires have been proposed in which the tread portion is composed of five land portions in the tire axial direction (hereinafter, sometimes referred to as "5-rib tires"). In addition, the pneumatic tire of the following Patent Document 1 is a 5-rib tire, and specifies lug grooves and sipes provided in the shoulder land portions, and is expected to improve wet performance and driving stability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-043637 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, with the trend toward higher performance and quieter operation of vehicles, there has been a demand for tires with improved driving stability and noise performance. In particular, in Europe, regulations on vehicle exterior noise have become stricter, and tires that can comply with these regulations are in demand.

[0005] The present disclosure has been made in consideration of the above circumstances, and has as its main object to provide a five-rib tire that can improve driving stability and noise performance. [Means for solving the problem]

[0006] The present disclosure relates to a tire having a tread portion, the tread portion including four circumferential grooves extending continuously in a tire circumferential direction between two tread ends, and five land portions divided into the four circumferential grooves, the two tread ends being edges of a contact surface under a 50% load when the tire is assembled to a normal rim with a normal internal pressure, and the tread portion is brought into contact with a flat surface with a camber angle of 0° under a load of 50% of a normal load, and each of the five land portions is not provided with a groove having a groove width exceeding 2.0 mm, and only sipes are provided, and the five land portions are provided with a front The tire includes a shoulder land portion including the tread edge, the four circumferential grooves include a shoulder circumferential groove adjacent to the shoulder land portion, the shoulder land portion is provided with a plurality of shoulder sipes extending from the shoulder circumferential groove to a position beyond the tread edge, at least one of the shoulder sipes includes an inclined portion extending from the shoulder circumferential groove at an angle to the tire axial direction, and an axial portion whose angle with respect to the tire axial direction is smaller than that of the inclined portion and is 10° or less, and the axial portion crosses the tread edge. Effect of the Invention

[0007] By adopting the above-described configuration, the tire of the present disclosure can improve steering stability and noise performance. [Brief description of the drawings]

[0008] [Figure 1] 1 is a development view of a tread portion showing one embodiment of the present disclosure. FIG. [Diagram 2] FIG. 2 is a meridian cross-sectional view including the rotation axis of the tire of FIG. 1. [Diagram 3] FIG. 2 is a cross-sectional view of a sipe. [Figure 4] FIG. 2 is an enlarged view of a first shoulder land portion and a first middle land portion of FIG. [Diagram 5] 5 is a cross-sectional view taken along line AA in FIG. 4. [Figure 6] 5 is a cross-sectional view taken along line BB in FIG. 4. [Figure 7] 5 is a cross-sectional view taken along line CC in FIG. 4. [Figure 8] 2 is an enlarged view of a second shoulder land portion and a second middle land portion of FIG. 1. FIG. [Figure 9] FIG. 9 is a cross-sectional view taken along line DD in FIG. 8. [Figure 10] 9 is a cross-sectional view taken along line EE in FIG. 8. [Figure 11] FIG. 2 is an enlarged view of the crown land portion of FIG. [Figure 12] FIG. 2 is an enlarged view showing the shape of the contact surface of the tread portion when the tread portion contacts the ground. [Figure 13] FIG. 2 is a development view of a tread portion of a tire of a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present disclosure will be described 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 be applied to a pneumatic tire for heavy loads and a non-pneumatic tire in which pressurized air is not filled inside the tire.

[0010] 1, a tread portion 2 of the present disclosure includes four circumferential grooves 3 extending continuously in the tire circumferential direction between two tread ends, and five land portions 4 divided by these circumferential grooves 3. That is, the tire 1 of the present disclosure is configured as a so-called five-rib tire in which the tread portion 2 is configured by the four circumferential grooves 3 and the five land portions 4. Hereinafter, in this specification, one of the two tread ends may be referred to as a first tread end T1, and the other may be referred to as a second tread end T2.

[0011] For example, the mounting orientation of the tread portion 2 of this embodiment on a vehicle is specified. 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 mounting orientation 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 mounting orientation on the vehicle may not be specified.

[0012] The first tread end T1 and the second tread end T2 each correspond to the ends of the contact surface at 50% load when 50% of the normal load is applied to the tire 1 in a 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 unloaded. 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 condition 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 set for each tire by each standard in the standard system on which the tire is based. In the case of JATMA, it is the "maximum air pressure." In the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." In the case of ETRTO, it is the "INFLATION PRESSURE."

[0016] In the case of pneumatic tires for which various standards are established, the "normal load" is the load that each standard specifies for each tire in the standard system that includes the standard on which the tire is based, and is the "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO. In addition, in the case of tires for which various standards are not established, the "normal load" refers to the maximum load that can be applied when using the tire in accordance with the above standards.

[0017] The circumferential groove 3 includes two shoulder circumferential grooves 5, 6 and two crown circumferential grooves 7, 8 provided between them. Hereinafter, in this specification, the shoulder circumferential groove arranged on the first tread edge T1 side may be referred to as the first shoulder circumferential groove 5, and the shoulder circumferential groove arranged on the second tread edge T2 side may be referred to as the second shoulder circumferential groove 6. The two crown circumferential grooves 7, 8 are arranged to sandwich the tire equator C. Hereinafter, in this specification, the crown circumferential groove arranged between the first shoulder circumferential groove 5 and the tire equator C may be referred to as the first crown circumferential groove 7, and the crown circumferential groove arranged between the second shoulder circumferential groove 6 and the tire equator C may be referred to as the second crown circumferential groove 8.

[0018] The axial distance L1 from the tire equator C to the groove centerline of the first shoulder circumferential groove 5 or the second shoulder circumferential groove 6 is preferably, for example, 20% to 30% of the tread width TW. The axial distance L2 from the tire equator C to the groove centerline 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] Each of the circumferential grooves 3 in this embodiment extends, for example, linearly in parallel to the tire circumferential direction. Each of the circumferential grooves 3 may extend, for example, in a wavy manner.

[0020] The groove width W1 of each circumferential groove 3 is desirably at least 3 mm. Also, the groove width W1 of each circumferential groove 3 is desirably, for example, 3.0% to 8.5% of the tread width TW. In this embodiment, the first shoulder circumferential groove 5 has the smallest groove width among the multiple circumferential grooves 3.

[0021] FIG. 2 is a meridian cross-sectional view of the rotation axis of the tire 1 of this embodiment. As shown in FIG. 2, 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. In a desirable embodiment, among the four circumferential grooves 3, the first shoulder circumferential groove 5 has the smallest depth. In a more desirable embodiment, the first crown circumferential groove 7, the second crown circumferential groove 8, and the second shoulder circumferential groove 6 are each configured as a flat groove whose depth is smaller than the groove width. However, the present disclosure is not limited to such an embodiment.

[0022] As shown in Fig. 1, each of the land portions 4 divided into the tread portion 2 does not have any grooves with a groove width exceeding 2.0 mm in the contact patch, and only sipes 9 are provided. The groove means a groove in which the area in a cross section where the distance between two groove walls exceeds 2.0 mm accounts for more than 50% of the total depth of the groove. Meanwhile, in this specification, a "sipe" means a small width cut having two inner walls extending in the tire radial direction, and in which the area in a cross section where the distance between the two inner walls is 2.0 mm or less accounts for 50% or more of the total depth of the cut.

[0023] Fig. 3 shows a cross-sectional view of a representative sipe 9 in this embodiment. As shown in Fig. 3, in the sipe 9, the width W2 between two sipe walls 9w that face each other and extend substantially parallel to each other is preferably 1.5 mm or less, and more preferably 0.4 to 1.0 mm. The total depth of the sipe 9 is, for example, 3.0 to 5.5 mm.

[0024] For example, at least one of the sipe edges on both sides of the sipe 9 may be formed as a chamfered portion 16. In the present embodiment, each of the sipe edges on both sides of the sipe 9 is formed as a chamfered portion 16. Hereinafter, such a sipe 9 may be referred to as a chamfered sipe. The chamfered portion 16 includes an inclined surface 17 that is continuous with the ground contact surface and the sipe wall 9w. The angle of the inclined surface 17 with respect to the depth direction of the sipe 9 is, for example, 30 to 60°.

[0025] The depth of the chamfered portion 16 is, for example, less than 30% of the total depth of the sipe 9, specifically 2.0 mm or less, more desirably 1.0 mm or less. If the chamfered portion 16 has such a depth, the opening width of the chamfered sipe may exceed 2.0 mm. In addition, in the present disclosure, the sipe 9 is not limited to the above-mentioned embodiment. Therefore, the sipe 9 may extend with a constant width from the opening of the ground contact surface to the bottom. In addition, the bottom of the sipe 9 may be connected to a flask bottom having a width exceeding 2.0 mm.

[0026] As shown in FIG. 1, the five land portions 4 of the present disclosure include at least one shoulder land portion including a tread edge. The five land portions 4 of the present embodiment include two shoulder land portions (a first shoulder land portion 11 and a second shoulder land portion 12). The first shoulder land portion 11 includes the first tread edge T1 and is located axially outward of the first shoulder circumferential groove 5. The second shoulder land portion 12 includes the second tread edge T2 and is located axially outward of the second shoulder circumferential groove 6. In the present embodiment, the five land portions 4 include two middle land portions (a first middle land portion 13 and a second middle land portion 14) and a crown land portion 15. The first middle land portion 13 is located between the first shoulder circumferential groove 5 and the first crown circumferential groove 7. The second middle land portion 14 is located between the second shoulder circumferential groove 6 and the second crown circumferential groove 8. The crown land portion 15 is divided between the first crown circumferential groove 7 and the second crown circumferential groove 8 .

[0027] Fig. 4 shows an enlarged view of the first shoulder land portion 11 and the first middle land portion 13. As shown in Fig. 4, at least one of the shoulder land portions of the present disclosure is provided with a plurality of shoulder sipes extending from the shoulder circumferential groove to a position beyond the tread end. As a more specific aspect, the first shoulder land portion 11 of the present embodiment is provided with a plurality of first shoulder sipes 20 extending from the first shoulder circumferential groove 5 to a position beyond the first tread end T1.

[0028] At least one of the shoulder sipes (first shoulder sipe 20) includes an inclined portion 21 and an axial portion 22. The inclined portion 21 extends from the first shoulder circumferential groove 5 at an angle with respect to the tire axial direction. The angle of the axial portion 22 with respect to the tire axial direction is smaller than that of the inclined portion 21 and is 10° or less. In the present disclosure, the axial portion 22 crosses the first tread edge T1, which is the edge of the contact patch at 50% load. In the present disclosure, the adoption of the above configuration makes it possible to improve steering stability and noise performance. The following mechanism is presumed to be the reason for this.

[0029] In the present disclosure, since no grooves with a groove width exceeding 2.0 mm are provided in each land portion 4 and only sipes 9 are provided, pattern noise is small and excellent noise performance is exhibited. In addition, such land portion 4 has high pattern rigidity and is also useful for improving steering stability.

[0030] In addition, since the first shoulder sipes 20 include the inclined portions 21, the entire edges of the first shoulder sipes 20 can come into contact with the ground with a time lag, and the noise made when these edges come into contact with the ground can be reduced.

[0031] In addition, in the present disclosure, since the axial portion 22 crosses the first tread edge T1, the axial rigidity of the land portion in the vicinity of the first tread edge T1 is not reduced by the first shoulder sipe 20, and excellent steering stability can be expected. In addition, such an axial portion 22 can provide a frictional force in the tire circumferential direction during braking by its edge. It is presumed that the above-mentioned mechanism in the present disclosure can improve noise performance and steering stability.

[0032] Hereinafter, a more detailed configuration of this embodiment will be described. Each configuration described below shows a specific aspect of this embodiment. Therefore, it goes without saying that the present disclosure can achieve the above-mentioned effects even if it does not have the configuration described below. In addition, even if any one of the configurations described below is applied alone to a tire of the present disclosure having the above-mentioned characteristics, an improvement in performance according to each configuration can be expected. Furthermore, when some of the configurations described below are applied in combination, a composite improvement in performance according to each configuration can be expected.

[0033] A one-pitch length P1 of the multiple first shoulder sipes 20 in the tire circumferential direction is, for example, 80% to 120% of a width W3 of the contact surface of the first shoulder land portion 11. Such an arrangement of the first shoulder sipes 20 helps to improve driving stability and noise performance in a well-balanced manner.

[0034] In this embodiment, the inclined portion 21 is inclined downward to the right with respect to the tire axial direction. Hereinafter, such a direction of inclination may be referred to as "inclined in a first direction with respect to the tire axial direction." The maximum angle θ1 of the inclined portion 21 with respect to the tire axial direction is, for example, 16.5 to 57.9°, and preferably 27.2 to 47.2°. Such an inclined portion 21 can improve responsiveness during steering while maintaining noise performance.

[0035] The axial portion 22 extends linearly, for example. The axial portion 22 is preferably disposed at an angle of 5° or less with respect to the tire axial direction, and more preferably disposed parallel to the tire axial direction. Such an axial portion 22 can provide a large frictional force during braking by its edges.

[0036] The distance L3 in the tire axial direction from the outer end 20a of the first shoulder sipe 20 to the first tread edge T1 is, for example, 25% to 55%, and preferably 30% to 50%, of the tire axial width W3 of the contact surface of the first shoulder land portion 11. Such an axial portion 22 can improve not only the driving stability and noise performance, but also the wandering performance.

[0037] The first shoulder sipe 20 desirably includes a curved portion 23 that extends between the inclined portion 21 and the axial portion 22. The curved portion 23 is, for example, an arc shape with a curvature radius of 10 to 40 mm. Such a curved portion 23 can suppress uneven wear of the first shoulder land portion 11.

[0038] The first shoulder sipe 20 is configured as the above-mentioned chamfered sipe, and the entire sipe edge on both sides is configured as a chamfered portion. In addition, in a plan view of the tread, the width of the chamfered portion 24 of the first shoulder sipe 20 increases toward the outside in the tire axial direction. Specifically, the chamfered portions of the inclined portion 21 and the axial portion 22 extend with a constant width, and the chamfered portion of the curved portion 23 increases in width toward the outside in the tire axial direction. As a result, in a plan view of the tread, the width of the chamfered portion of the axial portion 22 is larger than the width of the chamfered portion of the inclined portion 21. Specifically, the width of the chamfered portion of the axial portion 22 is 1.5 to 2.5 times the width of the chamfered portion of the inclined portion 21. The first shoulder sipe 20 having such a chamfered portion can effectively suppress uneven wear near the first tread edge T1. It goes without saying that the width of the chamfered portion described above means the width in a direction perpendicular to the length direction of the sipe in a plan view of the tread.

[0039] Fig. 5 shows a cross-sectional view taken along line AA in Fig. 4. As shown in Fig. 5, the first shoulder sipe 20 has a depth increasing from the inclined portion 21 toward the axial portion 22. The depth d2 of the inclined portion 21 is 40% to 60% of the maximum depth d1 of the axial portion 22. This improves the rigidity of the first shoulder land portion 11 on the axially inner side of the tire, thereby providing excellent steering stability.

[0040] 4, the first shoulder land portion 11 of this embodiment is provided with a plurality of shoulder-interrupted sipes 25. In this embodiment, the first shoulder sipes 20 and the shoulder-interrupted sipes 25 are provided alternately in the tire circumferential direction.

[0041] The shoulder-discontinuous sipe 25 extends from the first shoulder circumferential groove 5 and ends without reaching the first tread edge T1. For example, the shoulder-discontinuous sipe 25 ends axially inward of the axial portion 22 of the first shoulder sipe 20, and in a preferred embodiment, the shoulder-discontinuous sipe 25 ends axially inward of the curved portion 23 of the first shoulder sipe 20. In a more preferred embodiment, the shoulder-discontinuous sipe 25 ends without crossing the axial center position of the ground contact surface of the first shoulder land portion 11. The axial length L4 of the shoulder-discontinuous sipe 25 is, for example, 25% to 45% of the width W3 of the ground contact surface of the first shoulder land portion 11, and preferably 30% to 40%. Such a shoulder-discontinuous sipe 25 can further improve the driving stability and noise performance.

[0042] The shoulder-interrupted sipes 25 are inclined in a first direction with respect to the tire axial direction. That is, the shoulder-interrupted sipes 25 are inclined in the same direction as the inclined portion 21 of the first shoulder sipes 20. The angle θ3 of the shoulder-interrupted sipes 25 with respect to the tire axial direction is, for example, 16.5 to 57.9°, and preferably 27.2 to 47.2°. The angle difference between the shoulder-interrupted sipes 25 and the inclined portion 21 is, for example, 10° or less, and preferably 5° or less. As a more preferable aspect, in this embodiment, the shoulder-interrupted sipes 25 and the inclined portion 21 extend parallel to each other. This suppresses uneven wear of the first shoulder land portion 11.

[0043] The shoulder-disconnected sipes 25 are preferably configured as chamfered sipes. The chamfered portion of the shoulder-disconnected sipes 25 has a width that decreases from the first shoulder circumferential groove 5 side toward the tire axially outer side. As a result, the width of the chamfered portion of the shoulder-disconnected sipes 25 at the end of the chamfered portion on the inner side of the tire axial direction is larger than the width of the chamfered portion of the shoulder-disconnected sipes 25 at the end of the chamfered portion on the first shoulder circumferential groove 5 side of the shoulder-disconnected sipes 25 at the outer side of the tire axial direction. In a more preferable embodiment, the maximum width of the chamfered portion of the shoulder-disconnected sipes 25 is configured at the end of the shoulder-disconnected sipes 25 on the first shoulder circumferential groove 5 side, and is the same as the width of the chamfered portion of the inclined portion 21. In addition, the chamfered portion of the shoulder-disconnected sipes 25 has a width that decreases continuously from the position where the maximum width is configured toward the tire axially outer side.

[0044] Fig. 6 shows a cross-sectional view of line BB in Fig. 4. As shown in Fig. 6, the shoulder-interrupted sipe 25 includes a first portion 26 that communicates with the first shoulder circumferential groove 5, and a second portion 27 that communicates with the first portion 26 on the axially outer side of the tire and has a smaller depth than the first portion 26. The depth d4 of the second portion 27 is, for example, 60% to 75% of the depth d3 of the first portion 26. Such a shoulder-interrupted sipe 25 can maintain the rigidity of the first shoulder land portion 11 and can improve driving stability.

[0045] 4, the first middle land portion 13 is provided with a plurality of first middle sipes 30. A one-pitch length P2 of the plurality of first middle sipes 30 in the tire circumferential direction is, for example, 100% to 150% of a width W4 in the tire axial direction of the contact surface of the first middle land portion 13, and is the same as the one-pitch length P1 of the first shoulder sipes 20 in this embodiment.

[0046] The first middle sipes 30 are inclined with respect to the tire axial direction and completely cross the first middle land portion 13 in the tire axial direction. The first middle sipes 30 are, for example, inclined upward to the right with respect to the tire axial direction. Hereinafter, such a direction of inclination may be referred to as "inclined in a second direction with respect to the tire axial direction." In other words, the first middle sipes 30 are inclined in the opposite direction with respect to the tire axial direction to the inclined portion 21 of the first shoulder sipes 20.

[0047] The maximum angle θ2 of the first middle sipes 30 with respect to the tire axial direction is, for example, 15.9 to 65.3°, and preferably 28.6 to 52.6°. Such first middle sipes 30 can provide a well-balanced friction force in the tire circumferential and axial directions.

[0048] In this embodiment, the maximum angle θ1 of the inclined portion 21 of the first shoulder sipe 20 relative to the tire axial direction is set to be equal to or less than the maximum angle θ2 of the first middle sipe 30 relative to the tire axial direction. Moreover, the difference between the angles θ1 and θ2 is set to be 5° or less. Note that the angles θ1 and θ2 are absolute values ​​of acute angles formed by a virtual line extending parallel to the tire axial direction and the sipe, and the difference means a value obtained by subtracting the absolute value of the angle θ1 from the absolute value of the angle θ2.

[0049] When the angle between the inclined portion 21 of the first shoulder sipe 20 and the first middle sipe 30 has the above-mentioned relationship, the axial rigidity of each land portion of the tire of the first shoulder land portion 11 is equal to or slightly greater than that of the first middle land portion 13. Such a rigidity distribution enhances responsiveness and linearity during steering, and thus the handling stability can be further improved.

[0050] A distance L5 in the tire circumferential direction from an end 30a of the first middle sipe 30 on the first shoulder circumferential groove 5 side to an end 20b of the first shoulder sipe 20 on the first shoulder circumferential groove 5 side is, for example, 10% to 50%, and preferably 30% to 50%, of a one-pitch length P2 in the tire circumferential direction of the multiple first middle sipes 30. This improves steering stability and noise performance in a well-balanced manner.

[0051] Further, the distance in the tire circumferential direction from the end 30a of the first middle sipe 30 to the end 25a of the shoulder-interrupted sipe 25 on the first shoulder circumferential groove 5 side is, for example, 20% or less of the one pitch length P2, and preferably 10% or less. In this embodiment, the above-mentioned distance is substantially 0. In other words, the end 30a faces the end 25a.

[0052] The first middle sipe 30 is configured as, for example, a chamfered sipe. Specifically, the first middle sipe 30 has the entire sipe edge on both sides formed with a chamfered portion. In addition, in a plan view of the tread, the width of the chamfered portion of the first middle sipe 30 increases continuously toward the tire equator C side. As a result, the width of the chamfered portion is maximum at the end of the first middle sipe 30 on the tire equator C side. In a more preferable embodiment, the maximum width of the chamfered portion 31 of the first middle sipe 30 is larger than the maximum width of the chamfered portion of the inclined portion 21 of the first shoulder sipe 20. As a result, it is possible to improve the steering stability and noise performance while suppressing uneven wear of the first middle land portion 13.

[0053] FIG. 7 shows a cross-sectional view of line CC in FIG. 4. As shown in FIG. 7, the first middle sipe 30 includes, for example, a first middle tie bar 32 whose bottom is locally raised. The first middle tie bar 32 is arranged, for example, in a central region when the first middle sipe 30 is divided into three equal parts in the tire axial direction. The tire axial length L7 of the first middle tie bar 32 is 30% to 50% of the tire axial width W4 (shown in FIG. 4) of the ground contact surface of the first middle land portion 13. In addition, when the tire axial length of the first middle tie bar 32 varies in the tire radial direction, the length is measured at the center position in the tire radial direction. The depth d6 from the ground contact surface of the first middle land portion 13 to the outer surface of the first middle tie bar 32 is 50% to 70% of the maximum depth d5 ​​of the first middle sipe 30. Such a first middle tie bar 32 can maintain the rigidity of the first middle land portion 13 and can further improve the driving stability.

[0054] Fig. 8 shows an enlarged view of the second shoulder land portion 12 and the second middle land portion 14. As shown in Fig. 8, the second shoulder land portion 12 of this embodiment is provided with a plurality of shoulder sipes (second shoulder sipes 35) similar to the above-mentioned first shoulder sipes 20.

[0055] A one-pitch length P3 of the second shoulder sipes 35 in the tire circumferential direction is preferably smaller than a width W5 of the ground contact surface of the second shoulder land portion 12 in the tire axial direction, and specifically, is 60% to 80% of the width W5. The first pitch length P3 is 40% to 60% of a one-pitch length P1 (shown in FIG. 4) of the first shoulder sipes 20. As a result, the number of shoulder sipes (second shoulder sipes 35) arranged in the second shoulder land portion 12 is greater than the number of shoulder sipes (first shoulder sipes 20) arranged in the first shoulder land portion 11. Such an arrangement of sipes turns the impact sound when the first shoulder land portion 11 and the second shoulder land portion 12 contact the ground into white noise, improving noise performance.

[0056] The second shoulder sipe 35 extends from the second shoulder circumferential groove 6 to a position beyond the second tread edge T2. The second shoulder sipe 35 includes, for example, an inclined portion 41, an axial portion 42, and a curved portion 43. The inclined portion 41 extends from the second shoulder circumferential groove 6 at an angle. The angle of the axial portion 42 with respect to the tire axial direction is smaller than that of the inclined portion 41 and is 10° or less. The axial portion 42 crosses the second tread edge T2. The curved portion 43 extends in a curved manner between the axial portions 42. Such a second shoulder sipe 35 can improve steering stability and noise performance by a mechanism similar to that of the first shoulder sipe 20.

[0057] The configurations of the inclined portion 21, axial portion 22 and curved portion 23 of the first shoulder sipe 20 described above can be applied to the inclined portion 41, axial portion 42 and curved portion 43 of the second shoulder sipe 35, except for the matters described below.

[0058] The inclined portion 41 of the second shoulder sipe 35 is inclined in a first direction with respect to the tire axial direction. The maximum angle θ4 of the inclined portion 41 of the second shoulder sipe 35 in the tire axial direction is, for example, 16.5 to 53.7°, and preferably 26.1 to 44.1°. Moreover, the angle θ4 is preferably smaller than the angle θ1 of the inclined portion 21 of the first shoulder sipe 20. Moreover, the difference between the angle θ1 and the angle θ4 is preferably 5° or less. This makes it easier for the impact sound to become white noise when the first shoulder sipe 20 and the second shoulder sipe 35 come into contact with the ground, and noise performance can be improved.

[0059] The second shoulder sipes 35 include, for example, standard type second shoulder sipes 36 and small type second shoulder sipes 37. For the standard type second shoulder sipes 36, the axial distance L8 from the axial outer end 36a to the second tread edge T2 is preferably greater than the axial distance L3 (shown in FIG. 4) from the outer end 20a of the first shoulder sipe 20 to the first tread edge T1, and specifically is 125% to 140% of the distance L3.

[0060] The small second shoulder sipes 37 have a smaller axial length than the standard second shoulder sipes 36. The axial distance L9 from the outer end 37a of the small second shoulder sipes 37 to the second tread edge T2 is 15% to 25% of the distance L8 from the outer end 36a of the standard second shoulder sipes 36 to the second tread edge T2. In addition, in the second shoulder land portion 12 of this embodiment, the standard second shoulder sipes 36 and the small second shoulder sipes 37 are alternately provided in the tire circumferential direction. Such an arrangement of sipes helps to improve noise performance and wandering performance.

[0061] FIG. 9 shows a cross-sectional view of line DD in FIG. 8. As shown in FIG. 9, the standard type second shoulder sipe 36 includes, for example, a second shoulder tie bar 38 whose bottom is raised at a position away from the end on the second shoulder circumferential groove 6 side. The second shoulder tie bar 38 of this embodiment is provided, for example, at a position including at least a part of the curved portion 43. A depth d8 from the ground contact surface to the outer surface of the second shoulder tie bar 38 is 40% to 60% of the maximum depth d7 of the standard type second shoulder sipe 36. Such a second shoulder tie bar 38 helps maintain the rigidity of the second shoulder land portion 12 and improve driving stability.

[0062] FIG. 10 shows a cross-sectional view of line EE in FIG. 8. As shown in FIG. 10, the small second shoulder sipe 37 has a bottom that extends flat in its length direction. That is, the small second shoulder sipe 37 does not have a tie bar with a raised bottom. In this embodiment, by providing such small second shoulder sipe 37 and the above-mentioned standard type second shoulder sipe 36, the impact sound when these sipes touch the ground is turned into white noise, improving noise performance.

[0063] 8, the second middle land portion 14 is provided with a plurality of second middle sipes 40. The second middle sipes 40 can have the same configuration as the first middle sipes 30, except for the matters described below, and the description thereof will be omitted here.

[0064] The maximum angle θ5 of the second middle sipe 40 in the tire axial direction is preferably smaller than the maximum angle θ2 (shown in FIG. 4) of the first middle sipe 30 in the tire axial direction. In a more preferable embodiment, the absolute value |θ5-θ4| of the difference between the maximum angle θ5 of the second middle sipe 40 in the tire axial direction and the maximum angle θ4 of the inclined portion 41 of the second shoulder sipe 35 in the tire axial direction is preferably larger than the absolute value |θ2-θ1| of the difference between the maximum angle θ2 of the first middle sipe 30 in the tire axial direction and the maximum angle θ1 of the inclined portion 21 of the first shoulder sipe 20 in the tire axial direction. This makes it easier to turn the impact sound when each sipe touches the ground into white noise while suppressing uneven wear of each land portion, thereby improving wear resistance and noise performance.

[0065] FIG. 11 shows an enlarged view of the crown land portion 15 in FIG. 1. As shown in FIG. 11, the center position of the crown land portion 15 in the tire axial direction is located on the first tread edge T1 (shown in FIG. 1) side of the tire equator C. As a result, in the crown land portion 15, the width W7 of the ground contact surface of the outer region 15a on the first tread edge T1 side of the tire equator C is larger than the width W8 of the ground contact surface of the inner region 15b on the second tread edge T2 side of the tire equator C. Specifically, the width W7 of the outer region 15a is 51% to 55% of the width W6 of the ground contact surface of the crown land portion 15. Such a crown land portion 15 linearizes the change in cornering force accompanying the change in steering angle, and is useful for improving steering stability and ride comfort.

[0066] The crown land portion 15 is provided with a plurality of first crown sipes 46 and a plurality of second crown sipes 47. The first crown sipes 46 extend from the first crown circumferential groove 7, for example, and are terminated within the crown land portion 15. The second crown sipes 47 extend from the second crown circumferential groove 8, for example, and are terminated within the crown land portion 15.

[0067] The first crown sipe 46 and the second crown sipe 47 do not cross the axial center position of the crown land portion 15, and do not cross the tire equator C. The axial length L10 of the first crown sipe 46 or the second crown sipe 47 is, for example, 15% to 30% of the axial width W6 of the contact surface of the crown land portion 15. This reliably maintains the rigidity of the crown land portion 15, and provides excellent driving stability.

[0068] The first crown sipes 46 and the second crown sipes 47 are inclined in the second direction with respect to the tire axial direction, for example. The maximum angle θ6 of the first crown sipes 46 or the second crown sipes 47 with respect to the tire axial direction is, for example, 16.5 to 64.7°, and preferably 28.6 to 52.6°. In a more preferable embodiment, the angle difference between the first crown sipes 46 and the second crown sipes 47 is 5° or less, and in this embodiment, they are arranged parallel to each other. Such first crown sipes 46 and second crown sipes 47 can provide a well-balanced friction force in the tire circumferential direction and the tire axial direction.

[0069] In a more desirable embodiment, the maximum angle θ6 of the first crown sipe 46 or the second crown sipe 47 relative to the tire axial direction is desirably equal to or less than the angle θ2 (shown in FIG. 4) of the first middle sipe 30 relative to the tire axial direction, and is desirably equal to or greater than the angle θ5 (shown in FIG. 8) of the second middle sipe 40 relative to the tire axial direction. This improves noise performance while suppressing uneven wear of each land portion.

[0070] The first crown sipes 46 and the second crown sipes 47 are each configured as a chamfered sipe. In a preferred embodiment, the width of the chamfered portion of the first crown sipes 46 and the second crown sipes 47 becomes smaller toward the tire equator. Such first crown sipes 46 and the second crown sipes 47 can suppress uneven wear of the crown land portion 15.

[0071] In this embodiment, no sipes are provided in each land portion other than the above-mentioned sipes. This allows the above-mentioned various performances to be exhibited in a well-balanced manner. However, the present disclosure is not limited to such an embodiment.

[0072] FIG. 12 shows an enlarged view of the shape of the ground contact surface of the tread portion 2 of this embodiment when the tire is in contact with the ground. As shown in FIG. 12, when the tire is assembled to a regular rim with a regular internal pressure and is in contact with a flat surface with 50% of the regular load and a camber angle of 0° (hereinafter sometimes referred to as a "50% load state"), the width W1s of the ground contact surface in the tire axial direction of the first shoulder land portion 11 is preferably larger than the width W2s of the ground contact surface in the tire axial direction of the second shoulder land portion 12. Also, the width W1m of the ground contact surface in the tire axial direction of the first middle land portion 13 is preferably larger than the width W2m of the ground contact surface in the tire axial direction of the second middle land portion 14. Such a distribution of the land portion widths further improves the steering stability.

[0073] In a more preferable embodiment, when the widths of the ground contact surface in the tire axial direction of the first shoulder land portion 11, the first middle land portion 13, the crown land portion 15, the second middle land portion 14, and the second shoulder land portion 12 are W1s, W1m, Wc, W2m, and W2s, respectively, in the 50% load state, the following formula (1) is satisfied. Furthermore, as a more preferable embodiment, the tire 1 of the present embodiment also satisfies the following formula (2). In such a tire 1, the land portion close to the first tread end T1 has a higher rigidity. Therefore, even when the center of the ground contact surface moves toward the first tread end T1 due to steering, the steering response is stable, and a cornering force is generated linearly with respect to an increase in the steering angle. Therefore, excellent steering stability and ride comfort are obtained. W1m>Wc>W2m…(1) W1s>W1m>Wc>W2m≧W2s…(2)

[0074] Under a 50% load condition, the axial width W1s of the ground contact surface of the first shoulder land portion 11 is preferably 115% to 125% of the axial width Wc of the ground contact surface of the crown land portion 15. This optimizes the rigidity of the first shoulder land portion 11, and in addition to the above-mentioned effects, noise performance can also be improved.

[0075] From the same viewpoint, it is preferable that the axial width W1m of the ground contact surface of the first middle land portion 13 is 101% to 107% of the axial width Wc of the ground contact surface of the crown land portion 15 under a 50% load condition.

[0076] Under a 50% load condition, the axial width W2m of the ground contact surface of the second middle land portion 14 is preferably 90% to 99% of the axial width Wc of the ground contact surface of the crown land portion 15. This improves noise performance when traveling straight. Also, tire vibrations when traveling straight are less likely to be transmitted to the vehicle body, improving ride comfort.

[0077] From the same viewpoint, it is preferable that the axial width W2s of the ground contact surface of the second shoulder land portion 12 is 90% to 99% of the axial width Wc of the ground contact surface of the crown land portion 15 under a 50% load condition.

[0078] As a more preferable aspect, in this embodiment, under a 50% load condition, the width W2m of the second middle land portion 14 is set to be the same as the width W2s of the second shoulder land portion 12. This makes the wear progress of the second middle land portion 14 and the second shoulder land portion 12 uniform, improving uneven wear resistance.

[0079] 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 specific embodiment and can be modified and implemented in various aspects. EXAMPLES

[0080] A tire of size 235 / 45R19 having the basic pattern of FIG. 1 was prototyped based on the specifications of Table 1. In addition, as a comparative example, a tire was prototyped in which each shoulder sipe a does not include an axial portion as in the present disclosure, but is inclined in one direction and crosses the tread edge, as shown in FIG. 13. The comparative tire is substantially the same as the tire shown in FIG. 1, except for the above-mentioned points.

[0081] In addition, as a standard tire (reference tire) for comparing noise performance, a prototype tire was produced in which the width of each land portion of the tread portion was the same as that shown in FIG. 1 and no grooves or sipes were provided on each land portion.

[0082] Each test tire The steering stability and noise performance of the tires were tested. The common specifications and test methods for each test tire are as follows: Rim: 19 x 7.5J Tire pressure: front wheel 230kPa, rear wheel 210kPa Test vehicle: 2000cc, front-wheel drive Tire mounting position: All wheels

[0083] <Handling stability> The driving stability of the test vehicle when it was cornered on a dry road surface was evaluated by the driver. The results were evaluated as a score based on the driving stability of the comparative example being 100, with a higher value indicating better driving stability.

[0084] <Noise performance> The maximum sound pressure of the external noise was measured when the test vehicle was driven on a dry road at a speed of 70 km / h. The results are shown as an index in which the reduction in sound pressure, which is the difference from the sound pressure of the reference tire, is set to the reduction in sound pressure of the comparative example as 100. The larger the index, the smaller the maximum sound pressure of the noise, indicating excellent noise performance. The test results are shown in Table 1.

[0085] [Table 1]

[0086] As a result of the test, it was confirmed that the tires of the examples had improved steering stability and noise performance.

[0087] [Note] The present disclosure includes the following aspects.

[0088] [Disclosure 1] A tire having a tread portion, The tread portion includes four circumferential grooves extending continuously in the tire circumferential direction between two tread ends, and five land portions divided by the four circumferential grooves, The two tread ends are ends of a contact surface under a 50% load when the tire is mounted on a normal rim with a normal internal pressure, and the tread portion is brought into contact with a flat surface under a 50% load with a camber angle of 0°, Each of the five land portions is not provided with a groove having a groove width exceeding 2.0 mm, and only a sipe is provided, The five land portions include a shoulder land portion including the tread edge, the four circumferential grooves include a shoulder circumferential groove adjacent to the shoulder land portion, The shoulder land portion is provided with a plurality of shoulder sipes extending from the shoulder circumferential groove to a position beyond the tread end, At least one of the shoulder sipes includes an inclined portion extending from the shoulder circumferential groove at an angle with respect to the tire axial direction, and an axial portion whose angle with respect to the tire axial direction is smaller than that of the inclined portion and is equal to or smaller than 10°, The axial portion crosses the tread end. tire. [Disclosure 2] The tire as described in Disclosure 1, wherein the shoulder sipe includes a curved portion that extends curvedly between the inclined portion and the axial portion. [Disclosure 3] The tire according to Disclosure 3, wherein the curved portion is an arc having a radius of curvature of 10 to 40 mm. [Disclosure 4] At least one of the sipe edges on both sides of each of the inclined portion and the axial portion is formed as a chamfered portion, The tire according to any one of Disclosures 1 to 3, wherein, in a plan view of the tread, a width of the chamfered portion in the axial portion is larger than a width of the chamfered portion in the inclined portion. [Disclosure 5] The direction of installation on the vehicle is specified, The shoulder land portion includes a first shoulder land portion that is on the outer side of the vehicle when the vehicle is mounted thereon, The first shoulder land portion is provided with a plurality of shoulder-interrupted sipes extending from the shoulder circumferential groove and interrupted without reaching the tread end, The shoulder-interrupted sipe extends in the same direction as the inclined portion, The tire according to any one of Disclosures 1 to 4, wherein the shoulder-interrupted sipe is interrupted axially inward of the axial portion. [Disclosure 6] The shoulder-interrupted sipe has at least one of the sipe edges on both sides formed with a chamfered portion, The tire described in the present disclosure 5, wherein the width of the chamfered portion of the shoulder-interrupted sipe at the axially inner end of the chamfered portion is greater than the width of the chamfered portion of the shoulder-interrupted sipe at the axially outer end of the chamfered portion of the shoulder-interrupted sipe. [Disclosure 7] The direction of installation on the vehicle is specified, The shoulder land portion includes a first shoulder land portion that is on the outer side of the vehicle when the vehicle is installed, and a second shoulder land portion that is on the inner side of the vehicle when the vehicle is installed, The tire according to any one of Disclosures 1 to 6, wherein the number of the shoulder sipes arranged in the second shoulder land portion is greater than the number of the shoulder sipes arranged in the first shoulder land portion. [Disclosure 8] A tire as described in the present disclosure 7, wherein the angle of the inclined portion of the shoulder sipe provided in the second shoulder land portion relative to the tire axial direction is smaller than the angle of the inclined portion of the shoulder sipe provided in the first shoulder land portion relative to the tire axial direction. [Explanation of symbols]

[0089] 2 Tread section 3 Circumferential groove 4 Land 9 Sipe 5 Shoulder circumferential groove 11 Shoulder Land Section 20 Shoulder sipes 21 Slope 22 Axial section

Claims

1. A tire having a tread portion, The tread portion includes four circumferential grooves extending continuously in a tire circumferential direction between two tread ends, and five land portions divided by the four circumferential grooves, The two tread ends are ends of a contact surface under a 50% load when the tire is mounted on a normal rim with a normal internal pressure, and the tread portion is brought into contact with a flat surface under a 50% load with a camber angle of 0°, Each of the five land portions is not provided with a groove having a groove width exceeding 2.0 mm, and is provided with only sipes, The five land portions include a shoulder land portion including the tread edge, the four circumferential grooves include a shoulder circumferential groove adjacent to the shoulder land portion, The shoulder land portion is provided with a plurality of shoulder sipes extending from the shoulder circumferential groove to a position beyond the tread end, At least one of the shoulder sipes includes an inclined portion extending from the shoulder circumferential groove at an angle with respect to the tire axial direction, and an axial portion whose angle with respect to the tire axial direction is smaller than that of the inclined portion and is equal to or smaller than 10°, The axial portion crosses the tread end. tire.

2. The tire according to claim 1 , wherein the shoulder sipe includes a curved portion that extends curvedly between the inclined portion and the axial portion.

3. 3. The tire according to claim 2, wherein the curved portion is an arc having a radius of curvature of 10 to 40 mm.

4. At least one of the sipe edges on both sides of each of the inclined portion and the axial portion is formed as a chamfered portion, The tire according to claim 1 , wherein a width of the chamfered portion in the axial direction is larger than a width of the chamfered portion in the inclined portion in a plan view of the tread.

5. The direction of installation on the vehicle is specified, The shoulder land portion includes a first shoulder land portion that is on an outer side of the vehicle when the vehicle is mounted thereon, The first shoulder land portion is provided with a plurality of shoulder-interrupted sipes extending from the shoulder circumferential groove and interrupted without reaching the tread end, The shoulder-interrupted sipe extends in the same direction as the inclined portion, The tire according to claim 1 , wherein the shoulder-interrupted sipe is interrupted axially inward of the axial portion.

6. The shoulder-interrupted sipe has at least one of the sipe edges on both sides formed with a chamfered portion, 6. The tire according to claim 5, wherein a width of the chamfered portion of the shoulder-interrupted sipe at an axially inner end of the chamfered portion is greater than a width of the chamfered portion of the shoulder-interrupted sipe at an axially outer end of the chamfered portion of the shoulder-interrupted sipe.

7. The direction of installation on the vehicle is specified, The shoulder land portion includes a first shoulder land portion that is located on an outer side of the vehicle when the vehicle is mounted thereon, and a second shoulder land portion that is located on an inner side of the vehicle when the vehicle is mounted thereon, The tire according to claim 1 , wherein the number of the shoulder sipes arranged in the second shoulder land portion is greater than the number of the shoulder sipes arranged in the first shoulder land portion.

8. 8. The tire according to claim 7, wherein an angle of the inclined portion of the shoulder sipe provided in the second shoulder land portion with respect to the tire axial direction is smaller than an angle of the inclined portion of the shoulder sipe provided in the first shoulder land portion with respect to the tire axial direction.

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