JP2022173901A - tire - Google Patents

Abstract

To provide a tire improved in noise performance and wet performance.SOLUTION: A tire having a tread portion 2 is provided. The tread portion includes a first shoulder circumferential groove 5 and a first shoulder land portion 11. In the first shoulder land portion 11, a plurality of first shoulder sipes 20 extending from the first shoulder circumferential groove 5 to a position beyond a first tread end T1 are provided. In each of the first shoulder sipes 20, at least one of sipe edges on both sides is formed by a chamfered portion 22. In the chamfered portion 22, a chamfer width increases outward in a tire axial direction in a tread plan-view.SELECTED DRAWING: Figure 1

Description

The present invention relates to tires.

Conventionally, various pneumatic tires having shoulder land portions provided with a plurality of shoulder sipes have been proposed (for example, see Patent Document 1 below).

Japanese Unexamined Patent Application Publication No. 2012-017001

Shoulder sipes tend to produce less pitch noise when grounded and may contribute to improved noise performance. On the other hand, shoulder sipes have a small contribution to wet performance, and are required to be improved.

SUMMARY OF THE INVENTION The present invention has been devised in view of the actual situation as described above, and a main object of the present invention is to provide a tire with improved noise performance and wet performance.

The present invention provides a tire having a tread portion, wherein the tread portion includes a plurality of circumferential grooves extending continuously in the tire circumferential direction between a first tread end and a second tread end, a plurality of land portions divided into directional grooves, the plurality of circumferential grooves including a first shoulder circumferential groove arranged closest to the first tread end side, the plurality of land portions comprising the A first shoulder land portion including a first tread edge is provided with a plurality of first shoulder sipes extending from the first shoulder circumferential groove to a position beyond the first tread edge. At least one of sipe edges on both sides of each of the first shoulder sipes is formed by a chamfered portion, and the chamfered portion has a chamfered width that increases axially outward in the tread plan view. .

In the tire of the present invention, the chamfered portion includes a minimum chamfered width portion where the chamfered width is the minimum, and the minimum chamfered width portion is positioned axially inward of the first tread end. desirable.

In the tire of the present invention, the chamfered portion includes a maximum chamfered width portion where the chamfered width is maximum, and the maximum chamfered width portion is positioned axially outward of the first tread end. desirable.

In the tire of the present invention, the first shoulder land portion is provided with a plurality of interrupted shoulder sipes that extend from the first shoulder circumferential groove and are interrupted axially inward of the first tread end. is desirable.

In the tire of the present invention, it is preferable that the first shoulder land portion is not provided with a groove having 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 includes the A plurality of first middle sipes that completely cross the first middle land portion in the tire axial direction are provided, and at least one of sipe edges on both sides of each of the first middle sipes is formed with a chamfered portion. The chamfered portions are arranged on the inner widened portion where the chamfered width in the tread plan view increases toward the axially inner side of the tire, and on the axially outer side of the inner widened portion, and the chamfered width is on the axially outer side of the tire. and an outer widening that increases toward .

In the tire of the present invention, it is preferable that the maximum chamfer width of the inner widened portion is larger than the maximum chamfered 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 with respect to the tire axial direction.

In the tire of the present invention, the maximum angle of the first middle sipe with respect to the tire axial direction is preferably larger than the maximum angle of the first shoulder sipe with respect to the tire axial direction.

The tire of the present invention can improve noise performance and wet performance by adopting the above configuration.

1 is an exploded view of a tread portion showing an embodiment of the present invention; FIG. FIG. 2 is an enlarged view of a first shoulder land portion and a first middle land portion in FIG. 1; It is a cross-sectional view which shows one aspect|mode of a sipe. It is a cross-sectional view which shows another aspect of a sipe. It is an expansion perspective view of a 1st shoulder sipe. FIG. 3 is a cross-sectional view taken along line AA of FIG. 2; FIG. 2 is an enlarged view of a second shoulder land portion and a second middle land portion in FIG. 1; FIG. 2 is an enlarged view of the crown land portion of FIG. 1; FIG. 4 is an enlarged view showing the shape of the contact surface of the tread portion when contacting the ground; FIG. 3 is a developed view of a tread portion of a tire of a comparative example;

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a developed view of a tread portion 2 of a tire 1 showing one embodiment of the present invention. The tire 1 of the present embodiment is suitably used as, for example, a pneumatic tire for passenger cars. However, the present invention is not limited to such an aspect, and may be applied to a heavy-duty pneumatic tire or a non-pneumatic tire in which the inside of the tire is not filled with pressurized air.

As shown in FIG. 1, the tread portion 2 of the present invention includes a plurality of circumferential grooves 3 extending continuously in the tire circumferential direction between a first tread end T1 and a second tread end T2, and and a plurality of land portions 4 partitioned by directional grooves 3 . The tire 1 of the present 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 such an aspect.

For the tread portion 2 of the present embodiment, for example, the mounting direction to the vehicle is specified. Accordingly, the first tread end T1 is intended to be positioned on the outside of the vehicle when mounted on the vehicle. The second tread edge T2 is intended to be positioned on the inside of the vehicle when mounted on the vehicle. The mounting direction to the vehicle is indicated, for example, by characters or symbols on the sidewall portion (not shown). However, the tire 1 of the present invention is not limited to such an aspect, and may be one in which the mounting direction to the vehicle is not specified.

The first tread end T1 and the second tread end T2 are respectively ground contact surfaces (hereinafter referred to as , sometimes referred to as “grounding surface at 50% load”).

In the case of pneumatic tires that meet various standards, the term "normal condition" refers to a state in which the tire is mounted on a normal rim, inflated to a normal internal pressure, and unloaded. In the case of tires for which various standards are not defined or non-pneumatic tires, the normal condition means a standard usage condition according to the purpose of use of the tire, which is a condition in which the tire is not mounted on the vehicle and no load is applied. . In this specification, unless otherwise specified, the dimensions of each part of the tire are the values measured in the normal condition.

A "regular rim" is a rim defined for each tire in a standard system that includes standards on which tires are based. For ETRTO, it is "Measuring Rim".

"Regular internal pressure" is the air pressure specified for each tire by each standard in the standard system including the standards on which tires are based. Maximum value described in VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

In the case of pneumatic tires for which various standards have been established, the "regular load" is the load that each standard defines for each tire in the standard system including the standards that the tire is based on. "LOAD CAPACITY", 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 have not been established, the "normal load" refers to the maximum load that can be applied when using the tire according to the above-mentioned standards.

The circumferential grooves 3 include a first shoulder circumferential groove 5 arranged closest to the first tread end T1 among the plurality of circumferential grooves 3 . Furthermore, the circumferential grooves 3 of the present embodiment include second shoulder circumferential grooves 6 , first crown circumferential grooves 7 and second crown circumferential grooves 8 . The second shoulder circumferential groove 6 is located closest to the second tread end T2 among the plurality of circumferential grooves 3 . The first crown circumferential groove 7 is arranged between the first shoulder circumferential groove 5 and the tire equator C. As shown in FIG. The second crown circumferential groove 8 is arranged between the second shoulder circumferential groove 6 and the tire equator C. As shown in FIG.

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 20% to 30% of the tread width TW, for example. A tire axial distance L2 from the tire equator C to the groove center line of the first crown circumferential groove 7 or the second crown circumferential groove 8 is preferably 5% to 15% of the tread width TW, for example. The tread width TW is the distance in the tire axial direction from the first tread end T1 to the second tread end T2 in the normal state.

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

It is desirable that the groove width W1 of each circumferential groove 3 is at least 3 mm or more. Further, it is 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 plurality of circumferential grooves 3 .

The multiple land portions 4 include a first shoulder land portion 11 including a first tread edge T1. The first shoulder land portion 11 is divided outside the first shoulder circumferential groove 5 in the tire axial direction. Moreover, in the present embodiment, the plurality of land portions 4 includes 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 end T2 and is divided axially outward of the second shoulder circumferential groove 6 . The first middle land portion 13 is divided between the first shoulder circumferential groove 5 and the first crown circumferential groove 7 . The second middle land portion 14 is divided between the second shoulder circumferential groove 6 and the second crown circumferential groove 8 . The crown land portion 15 is divided between the first crown circumferential groove 7 and the second crown circumferential groove 8 .

FIG. 2 shows an enlarged view of the first shoulder land portion 11 and the first middle land portion 13. As shown in FIG. As shown in FIG. 4 , a sipe 9 is provided on the first shoulder land portion 11 . Specifically, the first shoulder land portion 11 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 edge T1.

FIG. 3 shows a cross-sectional view showing one aspect of the sipe 9 in this embodiment. FIG. 4 shows a cross-sectional view showing another aspect of the sipe 9 in this embodiment. As shown in FIGS. 3 and 4, as used herein, a "sipe" is a slit element having a small width, and the width W2 between two sipe walls 9w extending substantially parallel to each other and facing each other is 2.5mm. 0 mm or less. Also, "substantially parallel" means that the angle between the two sipe walls 9w is 10° or less. The width W2 of the sipe 9 is desirably 1.5 mm or less, and more desirably 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, at least one of the sipe edges on both sides of the sipe 9 may be formed with a chamfer 16, for example. Hereinafter, the sipe 9 whose entire sipe edge is formed by the chamfered portion 16 may be referred to as a chamfered sipe. The chamfered portion 16 includes an inclined surface 17 connecting 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 means the width of the inclined surface 17 provided on one sipe edge in a tread plan view (the width in the direction perpendicular to the length direction of the sipe).

The chamfered sipe opening width may exceed 2.0 mm. Further, 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 with 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, the ridge line 10 formed between the ground contact surface of the land portion and the sipe wall 9w having a width of less than 0.3 mm is treated as not having a chamfered portion. Further, in this specification, one sipe 9 including 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.

FIG. 5 shows an enlarged perspective view of the first shoulder sipe 20 cut along its center line. As shown in FIGS. 2 and 5 , at least one of the sipe edges on both sides of each of the first shoulder sipes, or both in this embodiment, is at least partially configured with a chamfered portion 22 . In addition, the chamfered width of the chamfered portion 22 of the first shoulder sipe 20 increases toward the outer side in the tire axial direction in the tread plan view. In the present invention, noise performance and wet performance can be improved by adopting the above configuration. The reason for this is presumed to be the following mechanism.

In the present invention, since the first shoulder land portion 11 is provided with the plurality of first shoulder sipes 20, the impact sound generated when the first shoulder land portion 11 touches the ground is reduced. Also, the first shoulder sipe 20 contributes to an improvement in noise performance because the pitch sound is small. In addition, two block pieces that are adjacent in the tire circumferential direction via the first shoulder sipe 20 are likely to come into contact with each other, so that they are less likely to vibrate when separated from the road surface, and noise caused by the vibration of these block pieces is suppressed. .

On the other hand, in a conventional tire, when the sipe arranged in the shoulder land portion is configured as a non-chamfered sipe, or even if it is a chamfered sipe, when the chamfered width of the chamfered portion is constant in the length direction of the sipe. , there was a tendency that sufficient drainage was not exhibited. In contrast, in the present invention, the chamfered width of the chamfered portion 22 of the first shoulder sipe 20 increases toward the outside in the tire axial direction. As a result, when the first shoulder sipe 20 contacts a wet road surface, the chamfered portion 22 can actively push away the water film axially outward of the tire, thereby exhibiting high drainage performance. It is believed that the present invention can exhibit excellent noise performance and wet performance due to such a mechanism.

A more detailed configuration of the present embodiment will be described below. Each configuration described below represents a specific aspect of the present embodiment. Therefore, it goes without saying that the present invention can exhibit the above effects even if it does not have the configuration described below. Further, even if any one of the configurations described below is applied singly to the tire of the present invention having the features described above, an improvement in performance corresponding to each configuration can be expected. Furthermore, when some of the respective configurations described below are applied in combination, it is possible to expect a combined improvement in performance according to each configuration.

As shown in FIG. 2, in this embodiment, at least in the first shoulder land portion 11, no groove having a groove width exceeding 2.0 mm is provided, and only the sipe 9 is provided. Further, as shown in FIG. 1, in a more desirable embodiment, each of the land portions 4 divided into the tread portion 2 is not provided with a groove having a groove width exceeding 2.0 mm in the contact surface. , and only the sipe 9 is provided. As a result, pitch noise due to grooves does not occur, and noise performance is improved.

The groove means that the groove width between the groove edges defined by the ground contact surface at 50% load exceeds at least 2.0 mm. More specifically, the groove has a groove width of more than 2.0 mm between the groove edges, and the distance between two groove walls in any of the upper, middle, and lower layers of the groove is is greater than 2.0 mm. The upper layer portion refers to a region closest to the contact surface when the groove is divided into three equal parts in the depth direction. The lower layer portion refers to a region closest to the bottom of the groove when the groove is divided into three equal parts in the depth direction. The intermediate layer section refers to a region between the upper layer section and the lower layer section.

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

The first shoulder sipe 20 is configured as a mixed sipe. That is, the first shoulder sipe 20 partially includes a region 21 configured as a non-chamfered sipe (hereinafter referred to as a non-chamfered region 21). In this embodiment, the non-chamfered region 21 of the first shoulder sipe 20 continues to 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 contact surface of the first shoulder land portion 11 . As a result, the reduction of the contact surface of the first shoulder land portion 11 caused by the chamfered portion 22 of the first shoulder sipe 20 is minimized, and excellent noise performance is obtained.

The chamfered portion 22 of the first shoulder sipe 20 continues to the axially outer side of the non-chamfered region 21 , and the chamfered width is continuously increased to the axially outer end of the first shoulder sipe 20 . As a result, of the chamfered portions 22, the minimum chamfered width portion 22a having the smallest chamfered width is located axially inward of the first tread end T1. On the other hand, of the chamfered portions 22, a maximum chamfered width portion 22b having the maximum chamfered width is located axially outward of the first tread end T1. As a result, the wet performance is improved, and the hitting sound generated when the edge of the first shoulder sipe 20 touches the ground near the first tread end T1 is reduced.

The axial distance L4 from the first tread end 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. . As a result, wet performance and noise performance are improved in a well-balanced manner.

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

From a similar point of view, the chamfered width of the chamfered portion 22 at the first tread edge T1 is 10% to 25%, preferably 15% to 20%, of the chamfered width of the maximum chamfered width portion 22b. The chamfer depth of the chamfered portion 22 at the first tread edge T1 is 10% to 25%, preferably 15% to 20%, of the chamfered depth of the maximum chamfered width portion 22b.

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

A plurality of interrupted shoulder sipes 25 are provided in the first shoulder land portion 11 of the present embodiment. The shoulder interrupted sipe 25 extends from the first shoulder circumferential groove 5 and is interrupted axially inward of the first tread end T1. The first shoulder sipes 20 and the interrupted shoulder sipes 25 are alternately provided in the tire circumferential direction. Such interrupted shoulder sipes 25 improve wet performance while maintaining the rigidity of the first shoulder land portion 11 .

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

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

A plurality of first middle sipes 30 are provided on the first middle land portion 13 . One pitch length P2 of the plurality of first middle sipes 30 in the tire circumferential direction is, for example, 100% to 150% of the axial width W5 of the contact surface of the first middle land portion 13. In this embodiment, It is the same as the one-pitch length P1 of the first shoulder sipe 20 .

The first middle sipe 30 is inclined with respect to the tire axial direction and completely crosses the first middle land portion 13 in the tire axial direction. The first middle sipe 30 is, for example, inclined in the first direction with respect to the tire axial direction. That is, the first shoulder sipe 20 and the first middle sipe 30 are inclined in the same direction with respect to the tire axial direction.

The maximum angle of the first middle sipe 30 with respect to the axial direction of the tire is, for example, 15-45°, preferably 25-35°. The maximum angle of the first middle sipe 30 with respect to the tire axial direction is preferably larger than the maximum angle of the first shoulder sipe 20 with respect to the tire axial direction. Such a first middle sipe 30 can exhibit frictional force in the axial direction of the tire, and is useful for enhancing turning performance on wet road surfaces.

A 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, a plurality of second It is 10% to 50%, preferably 30% to 50%, of the pitch length P2 of one middle sipe 30 in the tire circumferential direction. As a result, steering stability and noise performance are improved in a well-balanced manner.

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 side of the first shoulder circumferential groove 5 is, for example, 20% or less of the one pitch length P2. Yes, preferably 10% or less. In this embodiment, the above distance is substantially zero. 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 is formed by chamfering the entire sipe edges on both sides. 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 has, for example, a chamfered width that increases inward in the tire axial direction. The inner widened portion 32b of the present embodiment continues 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. there is The outer widened portion 32c has a chamfered width that increases outward in the tire axial direction. The outer widened width portion 32c of the present embodiment continues to the first shoulder circumferential groove 5 side of the constant width portion 32a, and the chamfered width increases continuously from the constant width portion 32a to the first shoulder circumferential groove 5. there is The first middle sipe 30 having such a chamfered portion 32 can positively push away the water film to both sides in the tire axial direction when the tire contacts a wet road surface.

The constant width portion 32a is provided, for example, in a position shifted from the center position of the first middle land portion 13 in the tire axial direction to the first tread end T1 side. Thus, 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. As shown in FIG. 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 shown in FIG. As a result, a large chamfered portion is formed on the tire equator C side of the first middle land portion 13, and the noise performance is further improved.

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

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

FIG. 6 shows a cross-sectional view taken along line AA of FIG. As shown in FIG. 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, 1.5-3.0 mm, preferably 2.0-2.5 mm. The maximum depth d3 of the outer widened portion 32c is 0.5-1.5 mm, preferably 0.9-1.3 mm. The depth d4 of the constant width portion 32a is, for example, 0.3-1.0 mm, preferably 0.4-0.6 mm.

The first middle sipe 30 includes, for example, a first middle tie bar 34 with a locally raised bottom. The first middle tie bar 34 is arranged, for example, in the center area when the first middle sipe 30 is divided into three equal parts in the axial direction of the tire. 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 contact surface of the first middle land portion 13 . 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. A depth d6 from the 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. As shown in FIG. Such a first middle tie bar 34 also helps reduce rolling resistance while improving noise performance.

FIG. 7 shows an enlarged view of the second shoulder land portion 12 and the second middle land portion 14. As shown in FIG. As shown in FIG. 7 , the second shoulder land portion 12 is provided with a plurality of second shoulder sipes 35 . The configuration of the first shoulder sipe 20 described above can be applied to the second shoulder sipe 35 of the present embodiment, and the description thereof is omitted here.

It is desirable that the second shoulder land portion 12 is provided with a plurality of narrow sipes 37 . The sipe width of the narrow sipe 37 is smaller than the sipe width of the second shoulder sipe 35 . Further, the narrow sipe 37 extends from the second shoulder circumferential groove 6 to a position beyond the second tread edge T2. However, the length of the small width sipe 37 in the axial direction of the tire is smaller than the length of the second shoulder sipe 35 in the axial direction of the tire. Further, the narrow sipe 37 is configured as a non-chamfered sipe. As a result, the noise generated when the second shoulder sipe 35 and the narrow sipe 37 touch the ground is likely to become white noise, and the noise performance and the wet performance are improved in a well-balanced manner.

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

A plurality of second middle sipes 40 are provided on the second middle land portion 14 . The configuration of the first middle sipe 30 described above can be applied to the second middle sipe 40, except for matters described below.

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

FIG. 8 shows an enlarged view of the crown land portion 15 of FIG. As shown in FIG. 8, the center position of the crown land portion 15 in the tire axial direction is positioned closer to the first tread end T1 (shown in FIG. 1) than the tire equator C. As shown in FIG. Accordingly, in the crown land portion 15, the width W9 of the contact surface of the outer region 15a on the first tread end T1 side of the tire equator C is equal to the contact surface of the inner region 15b on the second tread end T2 side of the tire equator C. width W10. 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. As shown in FIG. Such a crown land portion 15 makes the change in cornering force due to the change in steering angle linear, and serves 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 sipe 46 , for example, extends from the first crown circumferential groove 7 and is interrupted within the crown land portion 15 . The second crown sipe 47 , for example, extends from the second crown circumferential groove 8 and is interrupted within the crown land portion 15 .

The first crown sipe 46 and the second crown sipe 47 do not cross the center position of the crown land portion 15 in the tire axial direction and do not cross the tire equator C, respectively. 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 . As a result, the rigidity of the crown land portion 15 is reliably maintained, and excellent steering stability is exhibited.

The first crown sipe 46 and the second crown sipe 47 are, for example, inclined in the first direction with respect to the tire axial direction. The angle of the first crown sipe 46 or the second crown sipe 47 with respect to the tire axial direction is, for example, 20 to 30 degrees. In a more desirable aspect, the angular difference between the first crown sipe 46 and the second crown sipe 47 is 5° or less, and in this embodiment they are arranged in parallel. Such a first crown sipe 46 and a second crown sipe 47 can provide a well-balanced frictional force in the tire circumferential direction and the tire axial direction.

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

In this embodiment, no sipe is provided in each land portion other than the above-described sipe. As a result, the various performances described above are exhibited in a well-balanced manner. However, the present invention is not limited to such an aspect.

FIG. 9 shows an enlarged view showing the shape of the contact surface of the tread portion 2 of this embodiment when the contact surface is in contact with the ground. As shown in FIG. 9, in a state in which the rim is assembled on a regular rim with a regular internal pressure, 50% of the regular load is applied, and the ground surface is grounded on a flat surface with a camber angle of 0°, the first shoulder land portion 11 and the first shoulder land portion 11 When the widths of the contact surfaces of the first middle land portion 13, the crown land portion 15, the second middle land portion 14, and the second shoulder land portion 12 in the tire axial direction are W1s, W1m, Wc, W2m, and W2s, respectively, the widths are W1s is preferably larger than any of the widths W1m, Wc, W2m and W2s of the other land portions. Specifically, the width W1s is preferably 115 to 130% of the width Wc of the crown land portion 15. As shown in FIG. Thereby, the first shoulder land portion 11 has sufficiently high rigidity, and excellent steering stability is exhibited.

In this embodiment, the widths W1m, Wc, W2m, and W2s are configured to have sizes similar to each other. Specifically, each of the widths W1m, W2m and W2s is in the range of 90% to 110% of the width Wc of the crown land portion 15. As shown in FIG. Thereby, the uneven wear of each land part is suppressed.

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

A tire of size 235/45R19 having the basic pattern shown in FIG. Further, as a comparative example, as shown in FIG. 10, a trial tire was produced in which each shoulder sipe a was configured as a non-chamfered sipe.

As a reference tire for comparing noise performance (reference tire), the width of each land portion of the tread portion was the same as that shown in FIG. 1, and each land portion had grooves and sipes. A tire was prototyped that was not provided.

Each test tire was tested for noise performance and wet performance. Common specifications and test methods for each test tire are as follows.
Mounting rim: 19 x 7.5J
Tire internal 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 external noise was measured when the test vehicle was driven on a dry road surface at a speed of 70 km/h. As a result, the amount of sound pressure reduction, which is the difference from the sound pressure of the reference tire, is indicated by an index with the amount of sound pressure reduction of the comparative example set to 100. The larger the exponent, the smaller the maximum sound pressure of the noise, indicating that excellent noise performance is exhibited.

<Wet Performance>
The wet performance when the test vehicle was run on a wet road surface was evaluated by the driver's senses. The results are scored with the wet performance of the comparative example being 100, and the larger the number, the better the wet performance.
The results of the tests are shown in Table 1.

As a result of the test, it was confirmed that the tires of Examples 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 end T2 second tread end

Claims (9)

A tire having a tread portion,
The tread portion includes a plurality of circumferential grooves continuously extending in the tire circumferential direction between a first tread end and a second tread end, and a plurality of land portions divided into 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 including 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,
At least one of sipe edges on both sides of each of the first shoulder sipes is formed with a chamfered portion,
In the tread plan view, the chamfered portion has a chamfered width that increases outward in the axial direction of the tire.
tire. The chamfered portion includes a minimum chamfered width portion where the chamfered width is the minimum,
The tire according to claim 1, wherein the minimum chamfered width portion is located axially inward of the first tread end. 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 chamfered width portion is located axially outside of the first tread end. The first shoulder land portion is provided with a plurality of shoulder interrupted sipes that extend from the first shoulder circumferential groove and are interrupted axially inward of the first tread end. A tire according to any one of the above. The tire according to any one of claims 1 to 4, wherein the first shoulder land portion is not provided with grooves having a groove width exceeding 2.0 mm. the plurality of land portions including 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 axial direction of the tire,
At least one of sipe edges on both sides of each of the first middle sipes is formed with a chamfered portion,
The chamfered portion of the first middle sipe includes an inner widened portion in which the chamfered width in a tread plan view increases axially inward of the tire, and an axially outer side of the inner widened portion in the tire axial direction, and the chamfered width is: 6. The tire according to any one of claims 1 to 5, comprising an outer widened portion that increases axially outward. 7. Tire according to claim 6, wherein the maximum chamfer width of the inner widening is greater than the maximum chamfer width of the outer widening. The tire according to claim 6 or 7, wherein said first shoulder sipe and said first middle sipe are inclined in the same direction with respect to the tire axial direction. The tire according to any one of claims 6 to 8, wherein the maximum angle of the first middle sipe with respect to the tire axial direction is larger than the maximum angle of the first shoulder sipe with respect to the tire axial direction.

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