JP7669782B2 - tire - Google Patents

Description

The present invention relates to a tire.

Various pneumatic tires with multiple shoulder sipes in the shoulder land area have been proposed (see, for example, Patent Document 1 below).

JP 2012-017001 A

Shoulder sipes tend to reduce pitch noise when the tire touches the ground, and can contribute to improved noise performance. On the other hand, shoulder sipes have a small contribution to wet performance, and improvements are needed.

The present invention was devised in light of the above-mentioned circumstances, and its main objective is to provide a tire with improved noise and wet performance.

The present invention is a tire having a tread portion, the tread portion including a plurality of circumferential grooves extending continuously in the tire circumferential direction between a first tread edge and a second tread edge, and a plurality of land portions divided into the plurality of circumferential grooves, the plurality of circumferential grooves including a first shoulder circumferential groove arranged closest to the first tread edge, the plurality of land portions including the first tread edge, the first shoulder land portion including a plurality of first shoulder sipes extending from the first shoulder circumferential groove to a position beyond the first tread edge, each of the first shoulder sipes having at least one of the sipe edges on both sides formed with a chamfered portion, the chamfered width of the chamfered portion increasing toward the tire axially outer side in a plan view of the tread.

In the tire of the present invention, the chamfered portion includes a minimum chamfer width portion where the chamfer width is smallest, and it is preferable that the minimum chamfer width portion is located axially inward of the first tread edge.

In the tire of the present invention, it is preferable that the chamfered portion includes a maximum chamfer width portion where the chamfer width is maximum, and that the maximum chamfer width portion is located axially outboard of the first tread edge.

In the tire of the present invention, it is preferable that the first shoulder land portion is provided with a plurality of shoulder-interrupted sipes that extend from the first shoulder circumferential groove and terminate axially inward of the first tread edge.

In the tire of the present invention, it is preferable that the first shoulder land portion does not have grooves with a groove width exceeding 2.0 mm.

In the tire of the present invention, the plurality of land portions includes a first middle land portion adjacent to the first shoulder land portion via the first shoulder circumferential groove, and the first middle land portion is provided with a plurality of first middle sipes that completely cross the first middle land portion in the tire axial direction, and each of the first middle sipes has at least one of the sipe edges on both sides formed with a chamfered portion, and the chamfered portion of the first middle sipe preferably includes an inner widening portion whose chamfer width in a tread plan view increases toward the axially inner side of the tire, and an outer widening portion disposed axially outward of the inner widening portion and whose chamfer width increases toward the axially outer side of the tire.

In the tire of the present invention, it is desirable that the maximum chamfer width of the inner widened portion is greater than the maximum chamfer width of the outer widened portion.

In the tire of the present invention, it is preferable that the first shoulder sipe and the first middle sipe are inclined in the same direction relative to the tire axial direction.

In the tire of the present invention, it is desirable that the maximum angle of the first middle sipe relative to the tire axial direction is greater than the maximum angle of the first shoulder sipe relative to the tire axial direction.

By adopting the above-mentioned configuration, the tire of the present invention can improve noise performance and wet performance.

1 is a development view of a tread portion showing one embodiment of the present invention. FIG. 2 is an enlarged view of a first shoulder land portion and a first middle land portion of FIG. 1 . FIG. 2 is a cross-sectional view showing one embodiment of a sipe. FIG. 4 is a cross-sectional view showing another embodiment of a sipe. FIG. 2 is an enlarged perspective view of a first shoulder sipe. 3 is a cross-sectional view taken along line AA in FIG. 2. FIG. 2 is an enlarged view of a second shoulder land portion and a second middle land portion of FIG. 1 . FIG. 2 is an enlarged view of the crown land portion of FIG. FIG. 2 is an enlarged view showing the shape of the contact surface of the tread portion when the tread portion contacts the ground. FIG. 2 is a development view of a tread portion of a tire of a comparative example.

Below, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a development view of a tread portion 2 of a tire 1 showing one embodiment of the present invention. The tire 1 of this embodiment is preferably used, for example, as a pneumatic tire for passenger cars. However, the present invention is not limited to such an embodiment, and may also be applied to pneumatic tires for heavy loads and non-pneumatic tires that do not have pressurized air filled inside the tire.

As shown in FIG. 1, the tread portion 2 of the present invention includes a plurality of circumferential grooves 3 that extend 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 that are divided into these circumferential grooves 3. The tire 1 of this embodiment is configured as a so-called five-rib tire in which the tread portion 2 is composed of four circumferential grooves 3 and five land portions 4. However, the present invention is not limited to this aspect.

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 invention is not limited to this aspect, and the mounting orientation on the vehicle may not be specified.

The first tread edge T1 and the second tread edge T2 each correspond to the edge of the contact surface (hereinafter sometimes referred to as the "contact surface under 50% load") when the tire 1 in a normal state is loaded with 50% of the normal load and the tread portion 2 is in contact with a flat surface at a camber angle of 0°.

In the case of pneumatic tires for which various standards are established, the "normal state" refers to a state in which the tire is mounted on a normal rim, inflated to the normal internal pressure, and unloaded. In the case of tires for which various standards are not established or non-pneumatic tires, the normal state refers to a standard usage 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 state.

A "genuine rim" is a rim that is specified 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."

"Normal internal pressure" is the air pressure set for each tire by each standard in the standard system 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." For ETRTO, it is the "INFLATION PRESSURE."

In the case of pneumatic tires for which various standards are established, the "normal load" is the load that is established for each tire in the standard system that includes the standards on which the tire is based, and in the case of JATMA, it is the "maximum load capacity", in the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is the "LOAD CAPACITY". 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.

The circumferential grooves 3 include a first shoulder circumferential groove 5 that is disposed closest to the first tread edge T1 among the multiple circumferential grooves 3. Furthermore, the circumferential grooves 3 of this embodiment include a second shoulder circumferential groove 6, a first crown circumferential groove 7, and a second crown circumferential groove 8. The second shoulder circumferential groove 6 is disposed closest to the second tread edge T2 among the multiple circumferential grooves 3. The first crown circumferential groove 7 is disposed between the first shoulder circumferential groove 5 and the tire equator C. The second crown circumferential groove 8 is disposed between the second shoulder circumferential groove 6 and the tire equator C.

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.

In this embodiment, each circumferential groove 3 extends, for example, linearly in parallel to the tire circumferential direction. Each circumferential groove 3 may extend, for example, in a wavy manner.

It is desirable that the groove width W1 of each circumferential groove 3 is at least 3 mm. It is also desirable that the groove width W1 of each circumferential groove 3 is, 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.

The land portions 4 include a first shoulder land portion 11 including a first tread edge T1. The first shoulder land portion 11 is sectioned on the axially outer side of the first shoulder circumferential groove 5. In this embodiment, the land portions 4 include a second shoulder land portion 12, a first middle land portion 13, a second middle land portion 14, and a crown land portion 15. The second shoulder land portion 12 includes a second tread edge T2 and is sectioned on the axially outer side of the second shoulder circumferential groove 6. The first middle land portion 13 is sectioned between the first shoulder circumferential groove 5 and the first crown circumferential groove 7. The second middle land portion 14 is sectioned between the second shoulder circumferential groove 6 and the second crown circumferential groove 8. The crown land portion 15 is sectioned between the first crown circumferential groove 7 and the second crown circumferential groove 8.

Figure 2 shows an enlarged view of the first shoulder land portion 11 and the first middle land portion 13. As shown in Figure 4, the first shoulder land portion 11 is provided with sipes 9. Specifically, the first shoulder land portion 11 is provided with a plurality of first shoulder sipes 20 that extend from the first shoulder circumferential groove 5 to a position beyond the first tread edge T1.

Figure 3 shows a cross-sectional view of one aspect of the sipe 9 in this embodiment. Figure 4 shows a cross-sectional view of another aspect of the sipe 9 in this embodiment. As shown in Figures 3 and 4, in this specification, "sipe" means a cut element having a small width, in which the width W2 between two sipe walls 9w that face each other and extend approximately parallel to each other is 2.0 mm or less. Also, "approximately parallel" means an aspect in which the angle between the two sipe walls 9w is 10° or less. The width W2 of the sipe 9 is preferably 1.5 mm or less, and more preferably 0.4 to 1.0 mm. Also, the total depth d1 of the sipe 9 is, for example, 3.0 to 5.5 mm.

As shown in FIG. 3, the sipe 9 may have at least one of the sipe edges on both sides formed with a chamfered portion 16. Hereinafter, a sipe 9 whose entire sipe edge is formed with a chamfered portion 16 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°. The chamfer width W3 is, for example, 0.3 to 3.0 mm. The chamfer width W3 refers to the width of the inclined surface 17 provided on one sipe edge in a plan view of the tread (the width in the direction perpendicular to the length direction of the sipe).

The opening width of the chamfered sipe may exceed 2.0 mm. In addition, in the present invention, the bottom of the sipe 9 may be connected to a flask bottom having a width exceeding 2.0 mm.

As shown in FIG. 4, the sipe 9 may extend at a constant width from the opening of the ground contact surface to the bottom. In this specification, a sipe in which the entire sipe edge of the sipe 9 is configured in the shape shown in FIG. 4 may be referred to as a non-chamfered sipe. In this specification, a sipe in which the width of the ridge 10 formed between the ground contact surface of the land portion and the sipe wall 9w is less than 0.3 mm is treated as not having a chamfered portion. In this specification, a sipe 9 that includes the cross-sectional shape shown in FIG. 3 and the cross-sectional shape shown in FIG. 4 may be referred to as a mixed sipe.

Figure 5 shows an enlarged perspective view of the first shoulder sipe 20 cut along its center line. As shown in Figures 2 and 5, each of the first shoulder sipes has at least one of the sipe edges on both sides, and in this embodiment, both, at least a portion of which is configured with a chamfered portion 22. In addition, the chamfered portion 22 of the first shoulder sipe 20 has a chamfer width that increases toward the outside in the axial direction of the tire when viewed in a plan view of the tread. In the present invention, by adopting the above configuration, it is possible to improve noise performance and wet performance. The following mechanism is presumed to be the reason for this.

In the present invention, multiple first shoulder sipes 20 are provided on the first shoulder land portion 11, which reduces the impact noise when the first shoulder land portion 11 touches the ground. In addition, the first shoulder sipes 20 reduce pitch noise, which contributes to improved noise performance. In addition, two block pieces adjacent in the tire circumferential direction via the first shoulder sipes 20 tend to come into contact with each other, making them less likely to vibrate when they leave the road surface, and noise caused by the vibration of these block pieces is suppressed.

On the other hand, in conventional tires, when the sipes arranged in the shoulder land portion are configured as non-chamfered sipes, or when the chamfer width of the chamfered portion is constant along the length of the sipe, sufficient drainage tends to be not achieved. In contrast, in the present invention, the chamfered portion 22 of the first shoulder sipe 20 has a chamfer width that increases toward the outside in the axial direction of the tire. As a result, when the first shoulder sipe 20 contacts a wet road surface, the chamfered portion 22 can actively push the water film outward in the axial direction of the tire, thereby achieving high drainage. It is believed that this mechanism allows the present invention to achieve excellent noise performance and wet performance.

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

As shown in FIG. 2, in this embodiment, at least in the first shoulder land portion 11, no grooves with a groove width exceeding 2.0 mm are provided, and only sipes 9 are provided. Also, as shown in FIG. 1, in a more desirable embodiment, in each of the land portions 4 divided into the tread portion 2, no grooves with a groove width exceeding 2.0 mm are provided in the contact patch, and only sipes 9 are provided. This prevents pitch noise due to grooves, improving noise performance.

The groove means at least one in which the groove width between the groove edges, as defined by the 50% load contact surface, exceeds 2.0 mm. More specifically, the groove refers to one in which the groove width between the groove edges exceeds 2.0 mm, and the distance between the two groove walls exceeds 2.0 mm in any of the upper, middle, and lower layers of the groove. The upper layer refers to the area closest to the contact surface when the groove is divided into thirds in the depth direction. The lower layer refers to the area closest to the bottom of the groove when the groove is divided into thirds in the depth direction. The middle layer refers to the area between the upper layer and the lower layer.

As shown in FIG. 2, the circumferential pitch length P1 of the first shoulder sipe 20 is, for example, 90% to 120% of the axial width W4 of the contact surface of the first shoulder land portion 11.

The first shoulder sipe 20 is configured as a mixed sipe. That is, the first shoulder sipe 20 includes a region 21 (hereinafter referred to as the non-chamfered region 21) configured as a non-chamfered sipe. In this embodiment, the non-chamfered region 21 of the first shoulder sipe 20 is continuous with the first shoulder circumferential groove 5.

The axial length L3 of the non-chamfered region 21 of the first shoulder sipe 20 is, for example, 70% to 90% of the width W4 of the ground contact surface of the first shoulder land portion 11. This minimizes the reduction in the ground contact surface of the first shoulder land portion 11 caused by the chamfered portion 22 of the first shoulder sipe 20, resulting in excellent noise performance.

The chamfered portion 22 of the first shoulder sipe 20 is connected to the axially outer side of the non-chamfered region 21, and the chamfer width increases continuously up to the axially outer end of the first shoulder sipe 20. As a result, the minimum chamfer width portion 22a of the chamfered portion 22, where the chamfer width is smallest, is located axially inward of the first tread edge T1. On the other hand, the maximum chamfer width portion 22b of the chamfered portion 22, where the chamfer width is largest, is located axially outward of the first tread edge T1. This improves wet performance and reduces the impact noise when the edge of the first shoulder sipe 20 touches the ground near the first tread edge T1.

The axial distance L4 from the first tread edge T1 to the outer end of the first shoulder sipe 20 is, for example, 50% to 65% of the axial width W4 of the contact surface of the first shoulder land portion 11. This improves wet performance and noise performance in a well-balanced manner.

The chamfer width at the maximum chamfer width portion 22b is, for example, 1.5 to 3.0 mm, and preferably 2.0 to 2.5 mm. The chamfer depth at the maximum chamfer width portion 22b is, for example, 0.5 to 3.0 mm, and preferably 2.0 to 2.5 mm. The chamfer width and chamfer depth of the chamfer portion 22 on the first tread edge T1 are, for example, 0.3 to 1.0 mm, and preferably 0.4 to 0.6 mm. Such a chamfer portion 22 can improve noise performance and wet performance in a well-balanced manner.

From the same viewpoint, the chamfer width of the chamfered portion 22 at the first tread edge T1 is 10% to 25% of the chamfer width of the maximum chamfered width portion 22b, and preferably 15% to 20%. Also, the chamfer depth of the chamfered portion 22 at the first tread edge T1 is 10% to 25% of the chamfer depth of the maximum chamfered width portion 22b, and preferably 15% to 20%.

The angle of the first shoulder sipe 20 with respect to the tire axial direction is, for example, 10° or less. In this embodiment, the first shoulder sipe 20 is arranged downward to the right with respect to the tire axial direction. Hereinafter, in this specification, such an inclination direction may be referred to as inclining in a first direction with respect to the tire axial direction. In a desirable embodiment, the angle of the first shoulder sipe 20 is, for example, 3 to 10°.

In this embodiment, the first shoulder land portion 11 is provided with multiple shoulder-disconnected sipes 25. The shoulder-disconnected sipes 25 extend from the first shoulder circumferential groove 5 and are interrupted axially inward of the first tread edge T1. The first shoulder sipes 20 and the shoulder-disconnected sipes 25 are provided alternately in the tire circumferential direction. Such shoulder-disconnected sipes 25 improve wet performance while maintaining the rigidity of the first shoulder land portion 11.

The axial length L5 of the shoulder-disconnected sipe 25 is, for example, 40% to 70% of the axial width W4 of the ground contact surface of the first shoulder land portion 11, and preferably 50% to 60%. Such shoulder-disconnected sipes 25 improve driving stability and wet performance in a well-balanced manner.

The shoulder-disconnected sipes 25 are, for example, inclined in a first direction with respect to the tire axial direction. The angle of the shoulder-disconnected sipes 25 with respect to the tire axial direction is, for example, 3 to 10°. In this embodiment, the angle difference between the first shoulder sipes 20 and the shoulder-disconnected sipes 25 is 10° or less, and in a desirable embodiment, they are parallel. Such a sipe arrangement can suppress uneven wear of the first shoulder land portion 11.

The first middle land portion 13 is provided with a plurality of first middle sipes 30. The circumferential pitch length P2 of the plurality of first middle sipes 30 is, for example, 100% to 150% of the axial width W5 of the ground contact surface of the first middle land portion 13, and in this embodiment, is the same as the pitch length P1 of the first shoulder sipe 20.

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 inclined, for example, in a first direction with respect to the tire axial direction. That is, the first shoulder sipes 20 and the first middle sipes 30 are inclined in the same direction with respect to the tire axial direction.

The maximum angle of the first middle sipes 30 relative to the tire axial direction is, for example, 15 to 45°, and preferably 25 to 35°. The maximum angle of the first middle sipes 30 relative to the tire axial direction is preferably greater than the maximum angle of the first shoulder sipes 20 relative to the tire axial direction. Such first middle sipes 30 can also exert friction in the tire axial direction, which helps improve cornering performance on wet roads.

The distance L6 in the tire circumferential direction from the end 30a of the first middle sipe 30 on the side of the first shoulder circumferential groove 5 to the end 20a of the first shoulder sipe 20 on the side of the first shoulder circumferential groove 5 is, for example, 10% to 50% of the circumferential pitch length P2 of the multiple first middle sipes 30, and preferably 30% to 50%. This improves the steering stability and noise performance in a well-balanced manner.

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 side of the first shoulder circumferential groove 5 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.

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. The chamfered portion 32 of the first middle sipe 30 includes, for example, a constant width portion 32a, an inner widened portion 32b, and an outer widened portion 32c. The constant width portion 32a extends in the sipe length direction with a constant chamfer width. The inner widened portion 32b, for example, has a chamfer width that increases toward the inside in the tire axial direction. The inner widened portion 32b of this embodiment is connected to the first crown circumferential groove 7 side of the constant width portion 32a, and the chamfer width increases continuously from the constant width portion 32a to the first crown circumferential groove 7. The outer widened portion 32c has a chamfer width that increases toward the outside in the tire axial direction. In this embodiment, the outer widened portion 32c is connected to the constant width portion 32a on the first shoulder circumferential groove 5 side, and the chamfer width increases continuously from the constant width portion 32a to the first shoulder circumferential groove 5. The first middle sipe 30 having such a chamfered portion 32 can actively push water films out to both sides in the axial direction of the tire when the tire comes into contact with a wet road surface.

The constant width portion 32a is, for example, offset toward the first tread edge T1 side from the axial center position of the first middle land portion 13. As a result, the axial length L7 of the inner widened portion 32b is greater than the axial length L8 of the outer widened portion 32c. Specifically, the length L7 of the inner widened portion 32b is 40% to 60% of the width W5 of the ground contact surface of the first middle land portion 13. The length L8 of the outer widened portion 32c is 25% to 35% of the width W5 of the ground contact surface of the first middle land portion 13. As a result, a large chamfer is formed on the tire equator C side of the first middle land portion 13, further improving noise performance.

From the same viewpoint, it is desirable that the maximum chamfer width W6 of the inner widened portion 32b is larger than the maximum chamfer width W7 of the outer widened portion 32c. Specifically, the chamfer width W6 of the inner widened portion 32b is 1.3 to 2.0 times the chamfer width W7 of the outer widened portion 32c.

The maximum chamfer width W6 of the inner widened portion 32b is, for example, 1.5 to 3.0 mm, and preferably 2.0 to 2.5 mm. The maximum chamfer width W7 of the outer widened portion 32c is, for example, 0.5 to 1.5 mm, and preferably 0.9 to 1.3 mm. The chamfer width of the constant width portion 32a is, for example, 0.3 to 1.0 mm, and preferably 0.4 to 0.6 mm. However, the chamfer width is not limited to these dimensions.

Figure 6 shows a cross-sectional view taken along line A-A in Figure 2. As shown in Figure 6, the maximum depth d2 of the inner widened portion 32b is greater than the maximum depth d3 of the outer widened portion 32c. Specifically, the depth d2 of the inner widened portion 32b is 1.5 to 2.5 times the depth d3 of the outer widened portion 32c.

The maximum depth d2 of the inner widened portion 32b is, for example, 1.5 to 3.0 mm, and preferably 2.0 to 2.5 mm. The maximum depth d3 of the outer widened portion 32c is, for example, 0.5 to 1.5 mm, and preferably 0.9 to 1.3 mm. The depth d4 of the constant width portion 32a is, for example, 0.3 to 1.0 mm, and preferably 0.4 to 0.6 mm.

The first middle sipe 30 includes, for example, a first middle tie bar 34 whose bottom is locally raised. The first middle tie bar 34 is arranged, for example, in the central region when the first middle sipe 30 is divided into three equal parts in the tire axial direction. The axial length L9 of the first middle tie bar 34 is 30% to 50% of the axial width W5 (shown in FIG. 2) of the ground contact surface of the first middle land portion 13. Note that, when the axial length of the first middle tie bar 34 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 34 is 50% to 70% of the maximum depth d5 of the first middle sipe 30. Such a first middle tie bar 34 is also useful for reducing rolling resistance while improving noise performance.

Figure 7 shows an enlarged view of the second shoulder land portion 12 and the second middle land portion 14. As shown in Figure 7, the second shoulder land portion 12 is provided with a plurality of second shoulder sipes 35. The second shoulder sipes 35 of this embodiment can be configured in the same manner as the first shoulder sipes 20, and the description thereof will be omitted here.

It is preferable that a plurality of narrow sipes 37 are provided in the second shoulder land portion 12. The narrow sipes 37 have a smaller sipe width than the second shoulder sipes 35. The narrow sipes 37 extend from the second shoulder circumferential groove 6 to a position beyond the second tread edge T2. However, the axial length of the narrow sipes 37 is smaller than the axial length of the second shoulder sipes 35. The narrow sipes 37 are configured as non-chamfered sipes. This makes it easier for the noise generated when the second shoulder sipes 35 and the narrow sipes 37 make contact with the ground to become white noise, improving noise performance and wet performance in a well-balanced manner.

The narrow sipes 37 are, for example, inclined in a first direction relative to the tire axial direction. The angle of the narrow sipes 37 relative to the tire axial direction is, for example, 3 to 10 degrees. In this embodiment, the angle difference between the second shoulder sipes 35 and the narrow sipes 37 is 10 degrees or less, and in a desirable embodiment, they are parallel. Such a sipe arrangement helps to suppress uneven wear of the second shoulder land portion 12.

The second middle land area 14 is provided with a plurality of second middle sipes 40. The configuration of the first middle sipes 30 described above can be applied to the second middle sipes 40, except for the matters described below.

The second middle sipes 40 are inclined in a second direction opposite to the first direction with respect to the tire axial direction. The angle of the second middle sipes 40 with respect to the tire axial direction is, for example, 15 to 45 degrees, and preferably 25 to 35 degrees. Such second middle sipes 40 can improve cornering performance on wet road surfaces.

8 shows an enlarged view of the crown land portion 15 of FIG. 1. As shown in FIG. 8, the axial center position of the crown land portion 15 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 W9 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 W10 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 W9 of the outer region 15a is 51% to 55% of the width W8 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 helps to improve steering stability and ride comfort.

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, for example, from the first crown circumferential groove 7 and terminate within the crown land portion 15. The second crown sipes 47 extend, for example, from the second crown circumferential groove 8 and terminate within the crown land portion 15.

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 W8 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.

The first crown sipes 46 and the second crown sipes 47 are, for example, inclined in a first direction with respect to the tire axial direction. The angle of the first crown sipes 46 or the second crown sipes 47 with respect to the tire axial direction is, for example, 20 to 30°. In a more desirable 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.

The first crown sipes 46 and the second crown sipes 47 are each configured as non-chamfered sipes. Such first crown sipes 46 and second crown sipes 47 can suppress uneven wear of the crown land portion 15.

In this embodiment, no sipes are provided in each land portion other than the sipes described above. This allows the various performance characteristics described above to be exhibited in a well-balanced manner. However, the present invention is not limited to this embodiment.

9 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. 9, when the tire is assembled to a regular rim with regular internal pressure, and is in contact with the ground on a flat surface with a camber angle of 0° under a load of 50% of the regular load, 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. It is preferable that the width W1s is larger than the widths W1m, Wc, W2m, and W2s of the other land portions. Specifically, it is preferable that the width W1s is 115 to 130% of the width Wc of the crown land portion 15. This allows the first shoulder land portion 11 to have sufficiently high rigidity and exhibit excellent steering stability.

In this embodiment, the widths W1m, Wc, W2m, and W2s are configured to be approximately the same size. Specifically, the widths W1m, W2m, and W2s are each set to be in the range of 90% to 110% of the width Wc of the crown land portion 15. This suppresses uneven wear of each land portion.

The tire according to one embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment described above and can be modified and implemented in various ways.

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 was configured as a non-chamfered sipe, as shown in FIG. 10.

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

The noise and wet performance of each test tire was 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 displacement, front-wheel drive Tire mounting position: all wheels

<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.

<Wet performance>
The wet performance of the test vehicle when it was driven on a wet road surface was evaluated by the driver. The results are expressed as a score based on the wet performance of the comparative example being 100, with a higher value indicating better wet performance.
The results of the tests are shown in Table 1.

The test results confirmed that the tires of the embodiment had improved noise performance and wet performance.

2 tread portion 3 circumferential groove 4 land portion 5 first shoulder circumferential groove 11 first shoulder land portion 20 first shoulder sipe 22 chamfered portion T1 first tread edge T2 second tread edge

Claims (8)

A tire having a tread portion,
The tread portion includes a plurality of circumferential grooves extending continuously in a tire circumferential direction between a first tread edge and a second tread edge, and a plurality of land portions divided by the plurality of circumferential grooves,
The plurality of circumferential grooves include a first shoulder circumferential groove disposed closest to the first tread end,
the plurality of land portions include a first shoulder land portion including the first tread edge,
The first shoulder land portion is provided with a plurality of first shoulder sipes extending from the first shoulder circumferential groove to a position beyond the first tread edge, and a plurality of shoulder interrupted sipes extending from the first shoulder circumferential groove and interrupted axially inward of the first tread edge ,
Each of the first shoulder sipes has at least one of the sipe edges on both sides formed as a chamfered portion,
The chamfered portion has a chamfer width that increases toward the outside in the tire axial direction in a plan view of the tread ,
The axial length of the shoulder-interrupted sipe is 40% to 70% of the axial width of the ground contact surface of the first shoulder land portion .
tire. the chamfered portion includes a minimum chamfer width portion where the chamfer width is minimum,
The tire according to claim 1 , wherein the minimum chamfer width portion is located axially inward of the first tread edge. the chamfered portion includes a maximum chamfered width portion where the chamfered width is maximum,
The tire according to claim 1 or 2, wherein the maximum chamfer width portion is located axially outboard of the first tread edge. The tire according to claim 1 , wherein the first shoulder land portion is not provided with a groove having a width exceeding 2.0 mm. the plurality of land portions include a first middle land portion adjacent to the first shoulder land portion via the first shoulder circumferential groove,
The first middle land portion is provided with a plurality of first middle sipes that completely cross the first middle land portion in the tire axial direction,
Each of the first middle sipes has at least one of the sipe edges on both sides formed as a chamfered portion,
5. The tire according to claim 1, wherein the chamfered portion of the first middle sipe includes an inner widened portion in which a chamfer width in a tread plan view increases axially inward, and an outer widened portion arranged axially outward of the inner widened portion and in which the chamfer width increases axially outward . The tire according to claim 5 , wherein a maximum chamfer width of the inner widening portion is greater than a maximum chamfer width of the outer widening portion. The tire according to claim 5 or 6 , wherein the first shoulder sipes and the first middle sipes are inclined in the same direction with respect to the tire axial direction. The tire according to claim 5 , wherein a maximum angle of the first middle sipe with respect to the tire axial direction is larger than a maximum angle of the first shoulder sipe with respect to the tire axial direction.

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