JP2023078989A - tire - Google Patents

Abstract

To provide a tire capable of exerting excellent wet performance and noise performance.SOLUTION: A tire has a tread portion 2 designating a direction of installation to a vehicle. A first middle land part 11 is provided with at least one first middle sipe 16 completely crossing the first middle land part 11 in a tire axial direction. A second middle land part 12 is provided with at least one second middle sipe 17 completely crossing the second middle land part 12 in the tire axial direction. The first middle sipe 16 and the second middle sipe 17 respectively include sipe body portions 20 extending a tire radial direction, and chamfering portions 21 opening to a tread surface of a tread portion with a larger width than the sipe body portion 20. The chamfering portion of the first middle sipe 16 extends in the tire axial direction with a fixed chamfering width. The chamfering portion of the second middle sipe 17 increases a chamfering width from a position where the chamfering width is the minimum toward both sides in the tire axial direction.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to tires.

Patent Document 1 below proposes a tire provided with a sipe that completely traverses the middle land portion in the tire axial direction. The sipe is expected to improve the steering stability and noise performance of the tire.

JP 2015-137015 A

In recent years, vehicles have become quieter, and tires are required to have further improved noise performance. On the other hand, tires are required to have improved wet performance.

The present disclosure has been devised in view of the actual situation as described above, and a main object thereof is to provide a tire capable of exhibiting excellent wet performance and noise performance.

The present disclosure provides a tire having a tread portion with a specified mounting direction to a vehicle, wherein the tread portion includes a first tread end that is on the outside of the vehicle when mounted on the vehicle and a second tread end that is on the inside of the vehicle when mounted on the vehicle. A tread edge, a plurality of circumferential grooves continuously extending in the tire circumferential direction between the first tread edge and the second tread edge, and a plurality of land portions divided into the plurality of circumferential grooves. wherein the plurality of land portions includes a first middle land portion arranged between the first tread edge and the tire equator, and a second middle land portion arranged between the second tread edge and the tire equator. The first middle land portion is provided with at least one first middle sipe that completely crosses the first middle land portion in the axial direction of the tire, and the second middle land portion is provided with the At least one second middle sipe is provided that completely traverses the second middle land portion in the axial direction of the tire, and the first middle sipe and the second middle sipe are each composed of a sipe body portion extending in the tire radial direction and the sipe body portion extending in the tire radial direction. a chamfered portion opening to the tread surface of the tread portion with a width larger than the width of the body portion, the chamfered portion of the first middle sipe extending in the axial direction of the tire with a constant chamfered width, and the second middle sipe. The chamfered portion of is a tire in which the chamfered width increases from a position where the chamfered width is minimum toward both sides in the tire axial direction.

The tire of the present disclosure can exhibit excellent wet performance and noise performance by adopting the above configuration.

1 is an exploded view of a tread portion of a tire according to an embodiment of the present disclosure; FIG. 2 is an enlarged view of a first middle land portion, a second middle land portion and a crown land portion in FIG. 1; FIG. FIG. 3 is an enlarged view of a first middle sipe of FIG. 2; FIG. 3 is an enlarged view of a second middle sipe of FIG. 2; FIG. 3 is a cross-sectional view taken along line AA of FIG. 2; FIG. 3 is a cross-sectional view taken along line BB of FIG. 2; FIG. 3 is a cross-sectional view taken along line CC of FIG. 2; FIG. 2 is an enlarged view of a first shoulder land portion of FIG. 1; FIG. 9 is a cross-sectional view taken along line DD of FIG. 8; FIG. 2 is an enlarged view of a second shoulder land portion of FIG. 1; FIG. 4 is a developed view of the tread portion of the reference tire; FIG. 4 is a developed view of a tread portion of a comparative example;

An embodiment of the present disclosure 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 an embodiment of the present disclosure. The tire 1 of the present embodiment is suitably used as, for example, a pneumatic tire for passenger cars. However, the present disclosure is not limited to such an aspect, and may be applied to heavy-duty pneumatic tires and non-pneumatic tires that are not filled with pressurized air.

As shown in FIG. 1, the tread portion 2 of the tire 1 has a designated mounting direction to the vehicle. Thus, the tread portion 2 includes a first tread end T1 intended to be on the vehicle outer side when mounted on a vehicle, and a second tread end T2 intended to be on the vehicle inner side when mounted on the vehicle.

The first tread edge T1 and the second tread edge T2 are the edges of the contact surface when the tire 1 in the normal state is loaded with 70% of the normal load and the tread portion 2 is grounded on a flat surface with a camber angle of 0°. corresponds to

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 tread portion 2 includes a plurality of circumferential grooves 3 continuously extending in the tire circumferential direction between a first tread end T1 and a second tread end T2, and a plurality of land portions divided into a plurality of circumferential grooves 3. 4. The tire 1 of this embodiment is 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 disclosure is not limited to such an aspect. The tire 1 of another embodiment of the present disclosure may be a so-called 4-rib tire in which the tread portion 2 is composed of three circumferential grooves 3 and four land portions 4, for example.

The circumferential grooves 3 include a first shoulder circumferential groove 5 and a second shoulder circumferential groove 6 as well as a first crown circumferential groove 7 and a second crown circumferential groove 8 . The first shoulder circumferential groove 5 is located closest to the first tread end T1 among the plurality of circumferential grooves 3 . 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 provided between the first shoulder circumferential groove 5 and the tire equator C. As shown in FIG. The second crown circumferential groove 8 is provided 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 center line of the first shoulder circumferential groove 5 or the second shoulder circumferential groove 6 is preferably 25% to 35% 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 20% 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, the groove width W1 of each circumferential groove 3 is preferably 3.0% to 8.0% of the tread width TW. As a more desirable aspect, in this embodiment, among the plurality of circumferential grooves 3, the first shoulder circumferential groove 5 has the smallest groove width. However, the present disclosure is not limited to such an aspect.

The multiple land portions 4 include a first middle land portion 11 and a second middle land portion 12 . The first middle land portion 11 is arranged between the first tread edge T1 and the tire equator C. As shown in FIG. The first middle land portion 11 of this embodiment is divided between the first shoulder circumferential groove 5 and the first crown circumferential groove 7 . The second middle land portion 12 is arranged between the second tread end T2 and the tire equator C. As shown in FIG. The second middle land portion 12 of this embodiment is divided between the second shoulder circumferential groove 6 and the second crown circumferential groove 8 .

The plurality of land portions 4 of this embodiment include a first shoulder land portion 13 , a second shoulder land portion 14 and a crown land portion 15 . The first shoulder land portion 13 is divided axially outward of the first shoulder circumferential groove 5 and includes a first tread end T1. The second shoulder land portion 14 is divided axially outward of the second shoulder circumferential groove 6 and includes a second tread end T2. The crown land portion 15 is divided between the first crown circumferential groove 7 and the second crown circumferential groove 8 and is arranged on the tire equator C. As shown in FIG.

FIG. 2 shows an enlarged view of the first middle land portion 11, the second middle land portion 12 and the crown land portion 15. As shown in FIG. As shown in FIG. 2, the first middle land portion 11 is provided with at least one first middle sipe 16 that completely crosses the first middle land portion 11 in the tire axial direction. In this embodiment, the first middle land portion 11 is provided with a plurality of first middle sipes 16 . The second middle land portion 12 is provided with at least one second middle sipe 17 that completely crosses the second middle land portion 12 in the tire axial direction. In this embodiment, the second middle land portion 12 is provided with a plurality of second middle sipes 17 .

As used herein, the term "sipe" means a small width incision in which the width between two sipe walls in the sipe body is 1.5 mm or less. Further, the sipe body portion means a portion in which two sipe walls extend substantially parallel to each other in the tire radial direction. "Substantially parallel" means that the angle between two sipe walls is 10° or less. The sipes may include chamfers, as described below. The sipe may also have a so-called flask bottom with an increased width at the bottom.

An enlarged view of the first middle sipe 16 is shown in FIG. An enlarged view of the second middle sipe 17 is shown in FIG. 5 shows a sectional view taken along the line AA in FIG. 2 as a sectional view of the first middle sipe 16 or the second middle sipe 17. As shown in FIG. As shown in FIGS. 3 to 5 , the first middle sipe 16 and the second middle sipe 17 each have a sipe main body portion 20 extending in the tire radial direction and a sipe main body portion 20 having a width larger than that of the tread portion 2 . and a chamfered portion 21 opening into.

As shown in FIG. 3, in the present disclosure, the chamfered portion 21a of the first middle sipe 16 extends axially with a constant chamfered width W2. Further, as shown in FIG. 4, the chamfer width of the chamfered portion 21b of the second middle sipe 17 increases from the position where the chamfered width is minimum toward both sides in the tire axial direction. The tire 1 of the present disclosure can exhibit excellent wet performance and noise performance by adopting the above configuration. The reason for this is presumed to be the following mechanism.

In the tire 1 of the present disclosure, the first middle sipe 16 and the second middle sipe 17 that completely traverse the land provide frictional force during wet running and improve wet performance. In particular, since the first middle sipe 16 and the second middle sipe 17 include the chamfered portion 21, it becomes easier to guide the water film toward the circumferential groove 3 when the sipes contact the ground, and an improvement in wet performance can be expected.

In addition, the first middle sipe 16 and the second middle sipe 17 that cross the land portion cause air to flow in and out of the circumferential groove 3 by opening and closing the sipe during dry running, thereby preventing the generation of standing waves in the circumferential groove 3. can be suppressed. Such action can be expected to reduce air column resonance noise generated by the circumferential grooves 3 . In addition, since the chamfered portion 21a of the first middle sipe 16 and the chamfered portion 21b of the second middle sipe 17 have different shapes, the pitch sound when they touch the ground tends to become white noise, and an improvement in noise performance can be expected.

In addition, since the second middle sipe 17 is arranged closer to the second tread end T2 than the tire equator C, it tends to have a larger contact pressure than the first middle sipe 16, and contributes greatly to wet performance. In the present disclosure, since the width of the chamfered portion 21b of the second middle sipe 17 is increased toward both sides in the tire axial direction, the second middle sipe 17 can greatly contribute to improving wet performance. For this reason, the tire 1 of the present disclosure has a constant chamfered width of the chamfered portion of the second middle sipe and a variable chamfered width of the first middle sipe, thereby significantly improving wet performance. In the present disclosure, it is believed that such a mechanism enables excellent wet performance and noise performance to be exhibited.

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 disclosure 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 alone to the tire of the present disclosure having the features described above, an improvement in performance according 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. 5, in the first middle sipe 16 and the second middle sipe 17, the sipe main body portion 20 extends along the tire radial direction with a constant width, and preferably extends parallel to the tire radial direction. there is The width W3 of the sipe body 20 is, for example, 0.2-1.2 mm, preferably 0.4-0.8 mm. The sipe body portion 20 may extend in the tire radial direction while vibrating.

The chamfered portion 21 includes an inclined surface 25 that is inclined between the sipe main body portion 20 and the tread surface of the tread portion 2 . The chamfered portion 21 of this embodiment includes a pair of inclined surfaces 25 formed on both sipe edges, but the inclined surface 25 may be formed only on one sipe edge. The angle θ1 of the inclined surface 25 with respect to the normal to the tire is, for example, 55-80°, preferably 65-75°. In this specification, the chamfer width means the opening width of the sipe provided with the chamfer 21 on the tread surface of the tread portion 2, and is the difference between the width of the inclined surface 25 and the width of the sipe main body 20 in the tread plan view. Total equivalent.

As shown in FIG. 2, the first middle sipe 16 and the second middle sipe 17 are inclined in the same direction with respect to the tire axial direction. The angle of the first middle sipe 16 and the second middle sipe 17 with respect to the tire axial direction is, for example, 5 to 15 degrees. In a desirable aspect, the first middle sipe 16 and the second middle sipe 17 are inclined at the same angle with respect to the tire axial direction. Such first middle sipe 16 and second middle sipe 17 can improve wet performance while maintaining abrasion resistance.

As shown in FIG. 3 , the chamfered portion 21 a of the first middle sipe 16 is arranged along the entire length of the first middle sipe 16 . The chamfered portion 21a of the first middle sipe 16 includes a first inclined surface 26a connected to one sipe wall of the sipe body portion 20a and a second inclined surface 27a connected to the other sipe wall of the sipe body portion 20a. In this embodiment, in the first middle sipe 16, the first inclined surface 26a and the second inclined surface 27a have the same size. The chamfered width W2 of the chamfered portion 21a of the first middle sipe 16 is, for example, 1.0 to 2.0 mm.

As shown in FIG. 4 , the chamfered portion 21 b of the second middle sipe 17 is arranged along the entire length of the second middle sipe 17 . Also, the chamfered width of the second middle sipe 17 changes continuously. Such a second middle sipe 17 serves to suppress uneven wear of the land portion.

In the second middle sipe 17, it is desirable that the position where the chamfered width is the smallest is arranged, for example, in the center area when the second middle land portion 12 is divided into three equal parts in the axial direction of the tire. Such a second middle sipe 17 can guide the water film to the second shoulder circumferential groove 6 side and the second crown circumferential groove 8 side in a well-balanced manner during wet running.

The minimum chamfered width W4a of the chamfered portion 21b of the second middle sipe 17 is, for example, 1.0 to 2.0 mm. The chamfer width W4a of the present embodiment is the same as the chamfer width W2 of the first middle sipe 16. As shown in FIG. The maximum chamfered width W4b of the chamfered portion 21b of the second middle sipe 17 is preferably 1.5 times or more, more preferably 2.0 times or more, preferably 3.0 times or less, and more preferably the chamfered width W4a. is 2.5 times or less. As a result, wet performance and noise performance are improved in a well-balanced manner.

The chamfered portion 21b of the second middle sipe 17 includes a first inclined surface 26b connected to one sipe wall of the sipe body portion 20b and a second inclined surface 27b connected to the other sipe wall of the sipe body portion 20b. In the present embodiment, at the end portion 17b of the chamfered portion 21b of the second middle sipe 17 on the second tread end T2 side, the width of the first inclined surface 26b is smaller than the width of the second inclined surface 27b. At the end 17a of the chamfered portion 21b of the second middle sipe 17 on the side of the tire equator C, the width of the first inclined surface 26b is larger than the width of the second inclined surface 27b. In a more desirable mode, the width of the inclined surface at the portion where the groove wall of the circumferential groove 3 and the sipe wall of the second middle sipe 17 are connected to form an obtuse corner is is greater than the width of the slanted surface at the location where the sharp corner portion is formed. As a result, uneven wear at the end of the second middle sipe 17 is suppressed.

The first middle sipe 16 and the second middle sipe 17 each extend in the tire axial direction at a constant depth. In this embodiment, the first middle sipe 16 and the second middle sipe 17 have the same depth. Moreover, the depth of these sipes is desirably 60% to 80% of the depth of the circumferential groove 3, for example. As a result, wet performance and noise performance are improved in a well-balanced manner.

As shown in FIG. 2, it is desirable that the first middle land portion 11 is provided with, for example, a plurality of middle shallow grooves 30 . In this embodiment, the first middle sipes 16 and the middle shallow grooves 30 are alternately provided in the tire circumferential direction. The middle shallow groove 30 , for example, extends from the first shoulder circumferential groove 5 and discontinues within the first middle land portion 11 . The middle shallow groove 30 is discontinued on the first tread end T1 side of the center position of the first middle land portion 11 in the tire axial direction. The axial length L3 of the middle shallow groove 30 is, for example, 35% to 50% of the axial width W5 of the first middle land portion 11 . Such a shallow middle groove 30 improves wet performance and steering stability on a dry road surface (hereinafter sometimes simply referred to as "steering stability") in a well-balanced manner.

The middle shallow groove 30 is, for example, inclined in the same direction as the first middle sipe 16 with respect to the tire axial direction. The angle of the middle shallow groove 30 with respect to the tire axial direction is, for example, 5 to 15 degrees. In a more desirable mode, the angle difference between the first middle sipe 16 and the middle shallow groove 30 is 5° or less. This improves wet performance and noise performance while maintaining wear resistance performance.

FIG. 6 shows a cross-sectional view taken along line BB of FIG. As shown in FIG. 6, the groove depth d1 of the middle shallow groove 30 is, for example, 0.5 to 1.5 mm. A groove width W6 of the middle shallow groove 30 is, for example, 1.5 to 2.5 mm. In a more desirable aspect, the middle shallow groove 30 has a V-shaped cross-sectional shape in which two groove walls 30a inclined with respect to the tire radial direction are connected. The angle of the groove wall 30a with respect to the normal line of the tire is, for example, 30-50°. Such a shallow middle groove 30, for example, when turning on a wet road surface, the groove walls 30a contact the ground as the land portion deforms due to an increase in ground contact pressure, and wet performance can be improved.

As shown in FIG. 2, the second middle land portion 12 is provided with at least one semi-open middle sipe 33, for example. One end of the semi-open middle sipe 33 communicates with the second shoulder circumferential groove 6 and the other end is interrupted within the second middle land portion 12 . A plurality of semi-open middle sipes 33 are provided in the second middle land portion 12 of the present embodiment. Specifically, the second middle sipes 17 and the semi-open middle sipes 33 are provided alternately in the tire circumferential direction. It is

The semi-open middle sipe 33 is desirably discontinued on the second tread end T2 side of the center position of the second middle sipe 17 in the tire axial direction. The axial length L4 of the semi-open middle sipe 33 is, for example, 35% to 45% of the axial width W7 of the second middle land portion 12 . Such a semi-open middle sipe 33 can improve wet performance while maintaining steering stability.

The semi-open middle sipe 33 is, for example, inclined in the same direction as the second middle sipe 17 with respect to the tire axial direction. The angle of the semi-open middle sipe 33 with respect to the tire axial direction is, for example, 5 to 15 degrees. In a more desirable aspect, the angle difference between the second middle sipe 17 and the semi-open middle sipe 33 is 5° or less. This improves wet performance and noise performance while maintaining wear resistance performance.

The semi-open middle sipe 33 extends, for example, from the tread surface of the tread portion 2 to the bottom portion with a constant width. The depth of the semi-open middle sipe 33 is desirably smaller than the depth of the second middle sipe 17 . The depth of the semi-open middle sipe 33 is 20% or less of the maximum depth of the second middle sipe 17, specifically 0.5 to 1.5 mm. Such a semi-open middle sipe 33 can provide frictional force on wet road surfaces while maintaining wear resistance and steering stability.

The crown land portion 15 is provided with, for example, a plurality of first crown sipes 36 and second crown sipes 37 . The first crown sipe 36 extends from the first crown circumferential groove 7 and is interrupted within the crown land portion 15 . A second crown sipe 37 extends from the second crown circumferential groove 8 and is interrupted within the crown land portion 15 . First crown sipes 36 and second crown sipes 37 are alternately provided in the tire circumferential direction in the crown land portion 15 of the present embodiment. Such a first crown sipe 36 and a second crown sipe 37 serve to improve wet performance and noise performance in a well-balanced manner.

The first crown sipe 36 and the second crown sipe 37 are inclined in the same direction with respect to the tire axial direction, and in a preferred embodiment, are inclined in the same direction as the first middle sipe 16 and the second middle sipe 17 . The angle of the first crown sipe 36 and the second crown sipe 37 with respect to the tire axial direction is, for example, 10 to 20 degrees.

The first crown sipe 36 and the second crown sipe 37 cross the central position of the crown land portion 15 in the tire axial direction. The axial length L5 of the first crown sipe 36 and the axial length L6 of the second crown sipe 37 are each 55% to 70% of the axial width W8 of the crown land portion 15. is. In a more desirable embodiment, the length L6 of the second crown sipe 37 is greater than the length L5 of the first crown sipe 36. The length L6 is preferably 103% to 130% of the length L5, more preferably 103% to 115%. As a result, the wet performance can be enhanced, and the pitch sounds of the first crown sipe 36 and the second crown sipe 37 are likely to become white noise.

FIG. 7 shows a cross-sectional view taken along line CC of FIG. As shown in FIG. 7, first crown sipe 36 includes first sipe wall 23 and second sipe wall 24 . The first sipe wall 23 is a sipe wall that continues to the groove wall of the first crown circumferential groove 7 and forms an obtuse-angled corner portion in a plan view of the tread. The second sipe wall 24 is a sipe wall that continues to the groove wall of the first crown circumferential groove 7 and forms an acute-angled corner portion in a plan view of the tread.

The first sipe wall 23 includes a main body surface 23a forming the sipe main body portion 20c and an inclined surface 23b forming the chamfered portion 21c. The angle θ3 of the inclined surface 23b with respect to the tire normal line is, for example, 55 to 65°. Further, the second sipe wall 24 is connected to the tread surface of the crown land portion 15 without being chamfered. The first crown sipe 36 having such a chamfered portion 21c can enhance wet performance and wear resistance performance in a well-balanced manner.

As shown in FIG. 2, it is desirable that the width of the inclined surface 23b of the chamfered portion 21c of the first crown sipe 36 decreases toward the tire equator C side, for example. Thereby, when the first crown sipe 36 contacts the wet road surface, the water film can be actively guided to the first crown circumferential groove 7 .

The second crown sipe 37 has substantially the same configuration as the first crown sipe 36 . Therefore, the configuration of the first crown sipe 36 described above can be applied to the second crown sipe 37, and a description thereof will be omitted here.

FIG. 8 shows an enlarged view of the first shoulder land portion 13. As shown in FIG. As shown in FIG. 8 , the first shoulder land portion 13 is provided with, for example, a plurality of first shoulder lateral grooves 41 and a plurality of shoulder shallow grooves 45 .

The first shoulder lateral groove 41 , for example, extends axially inward from at least the first tread end T<b>1 and discontinues within the first shoulder land portion 13 . The first shoulder lateral groove 41 of this embodiment extends across the first tread edge T1. It is desirable that the angle of the first shoulder lateral groove 41 with respect to the tire axial direction increases axially inward. A distance L7 in the tire axial direction from the discontinuous end 41a of the first shoulder lateral groove 41 to the first shoulder circumferential groove 5 is 3% to 10% of the width W9 of the tread surface of the first shoulder land portion 13. As shown in FIG. Such first shoulder lateral grooves 41 serve to improve steering stability and wet performance in a well-balanced manner.

FIG. 9 shows a cross-sectional view taken along line DD of FIG. As shown in FIG. 9 , a chamfered portion 42 is provided in the first shoulder lateral groove 41 . The chamfered portion 42 includes an inclined surface 43 between the tread surface of the first shoulder land portion 13 and the groove wall 41w of the first shoulder lateral groove 41 . The angle θ4 of the inclined surface 43 with respect to the tire normal line is, for example, 35 to 55°. The width W10 of the inclined surface 43 and the depth d2 of the inclined surface 43 are preferably 0.2 to 0.7 mm, respectively. The first shoulder lateral groove 41 having such a chamfered portion 42 can exhibit excellent wear resistance performance.

As shown in FIG. 8, the inclined surface 43 of the chamfered portion 42 of the first shoulder lateral groove 41 increases the width W10 (shown in FIG. 9) outward in the tire axial direction around the first tread end T1. It is desirable that Specifically, on the first tread end T1, the width W10 of the inclined surface 43 is 20% to 30% of the width of the region of the first shoulder lateral groove 41 excluding the inclined surface 43. As shown in FIG. The width W10 of the inclined surface 43 at the axially outer end portion 41b of the first shoulder lateral groove 41 is 45% to 55% of the width of the region of the first shoulder lateral groove 41 excluding the inclined surface 43. . As a result, when a large load is applied to the tire, such as when turning, the inclined surface 43 is grounded to exhibit a large gripping force.

The shoulder shallow groove 45 , for example, extends from the first shoulder circumferential groove 5 and discontinues within the first shoulder land portion 13 . The shoulder shallow groove 45 of the present embodiment extends to the first tread end T1 side, for example, beyond the discontinuous end 41a of the first shoulder lateral groove 41 . Further, it is desirable that the axial length L8 of the shoulder shallow groove 45 is smaller than the axial length L3 of the middle shallow groove 30 (shown in FIG. 2). Specifically, the length L8 of the shoulder shallow groove 45 is 50% to 80% of the length L3 of the middle shallow groove 30. As shown in FIG. Such shallow shoulder grooves 45 serve to improve noise performance and wet performance in a well-balanced manner.

At the end of the shoulder shallow groove 45 on the side of the first shoulder circumferential groove 5 , the shoulder shallow groove 45 has substantially the same cross-sectional shape as the middle shallow groove 30 described above. Therefore, the configuration of the cross section of the middle shallow groove 30 described above can be applied to the shoulder shallow groove 45 . The width and depth of the shoulder shallow groove 45 decrease toward the first tread end T1. This improves wear resistance and steering stability.

FIG. 10 shows an enlarged view of the second shoulder land portion 14. As shown in FIG. As shown in FIG. 10 , the second shoulder land portion 14 is provided with, for example, a plurality of second shoulder lateral grooves 51 and a plurality of shoulder sipes 52 .

The second shoulder lateral groove 51 extends axially inward from at least the second tread end T<b>2 and discontinues within the second shoulder land portion 14 . The second shoulder lateral groove 51 of this embodiment extends across the second tread edge T2. The axial distance L9 from the discontinuous end 51a of the second shoulder lateral groove 51 to the second shoulder circumferential groove 6 is, for example, 10% to 20% of the width W11 of the tread surface of the second shoulder land portion . In a more desirable aspect, the distance L9 is greater than the axial distance L7 (shown in FIG. 8) from the interrupted end 41a of the first shoulder lateral groove 41 to the first shoulder circumferential groove 5. As shown in FIG. As a result, while steering stability and wet performance are improved in a well-balanced manner, the pitch sounds of the first shoulder lateral grooves 41 and the second shoulder lateral grooves 51 become white noise, and an improvement in noise performance can be expected.

The second shoulder lateral groove 51 has a chamfer similar to that of the first shoulder lateral groove 41 . Therefore, the configuration of the chamfered portion 42 of the first shoulder lateral groove 41 described above can be applied to the second shoulder lateral groove 51, and a description thereof will be omitted here.

The shoulder sipe 52 extends, for example, from the second shoulder circumferential groove 6 to a position beyond the second tread edge T2. The shoulder sipes 52 , for example, extend from the tread surface of the tread portion 2 to the bottom with a constant width. The depth of the shoulder sipe 52 is, for example, 0.5-1.5 mm. In a more desirable embodiment, the shoulder sipes 52 and the aforementioned semi-open middle sipes 33 (shown in FIG. 2) are of the same depth. Such shoulder sipes 52 can provide frictional force on wet road surfaces while maintaining steering stability and wear resistance performance.

In order to improve noise performance and wet performance in a well-balanced manner, as shown in FIG. 1, the land ratio of the tread portion 2 of the present embodiment is desirably 60% to 70%, for example. In this specification, the "land ratio" is the ratio Sb/Sa of the actual total ground contact area Sb to the total area Sa of the virtual ground contact area in which all grooves and sipes are filled.

Although the tire according to one embodiment of the present disclosure has been described in detail above, the present disclosure is not limited to the above-described specific embodiments, and can be implemented with various modifications.

A pneumatic tire of size 245/45R18 having the basic pattern shown in FIG. Also, a tire having a pattern shown in FIG. 11 was prototyped as a tire that serves as a reference for comparing noise performance (reference tire). As shown in FIG. 11, in this reference tire, compared with the pattern shown in FIG. 1, the first shoulder lateral grooves a and the second shoulder lateral grooves b communicate with the circumferential grooves, and the middle shallow grooves and the shoulder It does not have shallow grooves and each sipe does not have a chamfer.

Also, as a comparative example, a tire having the pattern shown in FIG. 12 was produced as a trial. As shown in FIG. 12, in the tire of the comparative example, the chamfered portions extend with a constant width in the first middle sipe c and the second middle sipe d. The tire of the comparative example is substantially the same as the tire of the example except for the above items. These test tires were also tested for wet performance and noise performance. Common specifications and test methods for each test tire are as follows.
Mounting rim: 18 x 8.0J
Tire pressure: 230kPa for all wheels
Test vehicle: 2000cc displacement, rear-wheel drive Tire mounting position: All wheels

<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.

<Noise performance>
The test vehicle was driven on a dry road surface at 40 to 100 km/h, and the maximum sound pressure of noise inside the vehicle was measured. 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.
The results of the tests are shown in Table 1.

As a result of the test, it was confirmed that the tires of Examples exhibited excellent wet performance and noise performance.

[Appendix]
The present disclosure includes the following aspects.

[Present Disclosure 1]
A tire having a tread portion with a specified orientation for mounting on a vehicle,
The tread portion includes a first tread end on the outside of the vehicle when mounted on a vehicle, a second tread end on the inside of the vehicle when mounted on the vehicle, and a tire circumferential direction between the first tread end and the second tread end. including a plurality of continuously extending circumferential grooves and a plurality of land portions divided into the plurality of circumferential grooves,
The plurality of land portions include a first middle land portion arranged between the first tread edge and the tire equator, and a second middle land portion arranged between the second tread edge and the tire equator. including
The first middle land portion is provided with at least one first middle sipe that completely crosses the first middle land portion in the tire axial direction,
The second middle land portion is provided with at least one second middle sipe that completely crosses the second middle land portion in the tire axial direction,
The first middle sipe and the second middle sipe each include a sipe main body portion extending in the tire radial direction and a chamfered portion opening to the tread surface of the tread portion with a width larger than the width of the sipe main body portion,
The chamfered portion of the first middle sipe extends in the tire axial direction with a constant chamfered width,
In the chamfered portion of the second middle sipe, the chamfered width increases from a position where the chamfered width is minimum toward both sides in the tire axial direction.
tire.
[Disclosure 2]
The tire according to the present disclosure 1, wherein the chamfer width of the second middle sipe varies continuously.
[Disclosure 3]
3. The tire according to the present disclosure 1 or 2, wherein the chamfered portion of the first middle sipe is arranged along the entire length of the first middle sipe.
[Disclosure 4]
4. The tire according to any one of the present disclosures 1 to 3, wherein the chamfered portion of the second middle sipe is arranged along the entire length of the second middle sipe.
[Disclosure 5]
5. The tire according to any one of the present disclosure 1 to 4, wherein the maximum chamfered width of the chamfered portion of the second middle sipe is larger than the chamfered width of the chamfered portion of the first middle sipe.
[Disclosure 6]
6. The tire according to any one of the present disclosures 1 to 5, wherein the first middle sipe and the second middle sipe are inclined in the same direction with respect to the tire axial direction.
[Present Disclosure 7]
7. The tire according to the present disclosure 6, wherein the first middle sipe and the second middle sipe are inclined at the same angle with respect to the tire axial direction.
[Disclosure 8]
The chamfered portion of the first middle sipe and the chamfered portion of the second middle sipe have a first inclined surface that continues to one sipe wall of the sipe body portion and a second inclined surface that continues to the other sipe wall of the sipe body portion. including faces and
7. The width of the first inclined surface is smaller than the width of the second inclined surface at the end of the chamfered portion of the second middle sipe on the second tread end side according to any one of the present disclosures 1 to 6. tires.
[Disclosure 9]
9. The tire according to the present disclosure 8, wherein the width of the first inclined surface is greater than the width of the second inclined surface at the tire equator-side end of the chamfered portion of the second middle sipe.
[Disclosure 10]
1 to 1 of the present disclosure, wherein the second middle land portion is provided with at least one semi-open middle sipe, one end of which communicates with the circumferential groove and the other end of which is interrupted within the second middle land portion. 9. The tire according to any one of 9.
[Present Disclosure 11]
11. The tire according to the present disclosure 10, wherein the semi-open middle sipe extends from the tread surface of the tread portion to the bottom portion with a constant width.

2 tread portion 3 circumferential groove 4 land portion 11 first middle land portion 12 second middle land portion 16 first middle sipe 17 second middle sipe 20 sipe body portion 21 chamfered portion T1 first tread end T2 second tread end

Claims (11)

A tire having a tread portion with a specified orientation for mounting on a vehicle,
The tread portion includes a first tread end on the outside of the vehicle when mounted on a vehicle, a second tread end on the inside of the vehicle when mounted on the vehicle, and a tire circumferential direction between the first tread end and the second tread end. including a plurality of continuously extending circumferential grooves and a plurality of land portions divided into the plurality of circumferential grooves,
The plurality of land portions include a first middle land portion arranged between the first tread edge and the tire equator, and a second middle land portion arranged between the second tread edge and the tire equator. including
The first middle land portion is provided with at least one first middle sipe that completely crosses the first middle land portion in the tire axial direction,
The second middle land portion is provided with at least one second middle sipe that completely crosses the second middle land portion in the tire axial direction,
The first middle sipe and the second middle sipe each include a sipe main body portion extending in the tire radial direction and a chamfered portion opening to the tread surface of the tread portion with a width larger than the width of the sipe main body portion,
The chamfered portion of the first middle sipe extends in the tire axial direction with a constant chamfered width,
In the chamfered portion of the second middle sipe, the chamfered width increases from a position where the chamfered width is minimum toward both sides in the tire axial direction.
tire. 2. The tire of claim 1, wherein said chamfer width of said second middle sipe varies continuously. The tire according to claim 1 or 2, wherein the chamfered portion of the first middle sipe is arranged along the entire length of the first middle sipe. The tire according to any one of claims 1 to 3, wherein the chamfered portion of the second middle sipe is arranged along the entire length of the second middle sipe. The tire according to any one of claims 1 to 4, wherein the maximum chamfered width of the chamfered portion of the second middle sipe is larger than the chamfered width of the chamfered portion of the first middle sipe. The tire according to any one of claims 1 to 5, wherein the first middle sipe and the second middle sipe are inclined in the same direction with respect to the tire axial direction. 7. The tire according to claim 6, wherein said first middle sipe and said second middle sipe are inclined at the same angle with respect to the tire axial direction. The chamfered portion of the first middle sipe and the chamfered portion of the second middle sipe have a first inclined surface that continues to one sipe wall of the sipe body portion and a second inclined surface that continues to the other sipe wall of the sipe body portion. including faces and
7. The width of the first inclined surface is smaller than the width of the second inclined surface at the end of the chamfered portion of the second middle sipe on the second tread end side. The tires described in . The tire according to claim 8, wherein the width of the first inclined surface is greater than the width of the second inclined surface at the tire equator-side end of the chamfered portion of the second middle sipe. 2. The second middle land portion is provided with at least one semi-open middle sipe, one end of which communicates with the circumferential groove and the other end of which is interrupted within the second middle land portion. 10. The tire according to any one of 9. The tire according to claim 10, wherein the semi-open middle sipe extends from the tread surface of the tread portion to the bottom portion with a constant width.

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