JP7779108B2 - tire - Google Patents

Description

This disclosure relates to tires.

Patent Document 1 below proposes a pneumatic tire with shallow grooves in the outer shoulder land area. The shallow grooves are expected to improve cornering performance when driving on wet roads.

Japanese Patent Application Laid-Open No. 2018-043637

In recent years, there has been a demand for further improvements in the wet performance of tires. However, conventional methods for improving wet performance have the potential to result in a decrease in wear resistance.

This disclosure was devised in light of the above-mentioned circumstances, and its primary objective is to provide a tire that can exhibit excellent wet performance while maintaining wear resistance.

The present disclosure relates to a tire having a tread portion, the tread portion including a circumferential groove extending continuously in the tire circumferential direction and at least one land portion adjacent to the circumferential groove, the land portion having at least one shallow groove communicating with the circumferential groove, the shallow groove having a pair of groove walls arranged in a V-shape in a cross section perpendicular to the longitudinal direction of the shallow groove, the shallow groove having a groove width of 1.5 to 2.5 mm, and the pair of groove walls being inclined at an angle of 30 to 50 degrees with respect to a tread normal extending from the groove edge of the shallow groove.

By adopting the above configuration, the tire disclosed herein is able to exhibit excellent wet performance while maintaining wear resistance.

1 is a development view of a tread portion of a tire according to one embodiment of the present disclosure. FIG. 2 is an enlarged view of a first middle land portion and a second shoulder land portion of FIG. 1 . FIG. 3 is an enlarged view of the shallow groove of FIG. 2 . 3 is a cross-sectional view taken along line BB in FIG. 2. 3 is a cross-sectional view taken along line DD in FIG. 2. 2 is an enlarged view of a first middle land portion, a second middle land portion, and a crown land portion of FIG. 1 . FIG. 7 is an enlarged view of the first middle sipe of FIG. 6 . FIG. 7 is an enlarged view of the second middle sipe of FIG. 6 . 7 is a cross-sectional view taken along line AA in FIG. 6. 7 is a cross-sectional view taken along line CC in FIG. 6. FIG. 2 is an enlarged view of a second shoulder land portion of FIG. 1 . FIG. 2 is a development view of a tread portion of a comparative example.

An embodiment of the present disclosure will now be described with reference to the drawings. FIG. 1 is a developed view of a tread portion 2 of a tire 1 illustrating one embodiment of the present disclosure. The tire 1 of this embodiment is suitable for use, for example, as a pneumatic tire for passenger vehicles. However, the present disclosure is not limited to this embodiment and may also be applied to pneumatic tires for heavy loads and non-pneumatic tires that do not contain pressurized air inside the tire.

As shown in FIG. 1, the tread portion 2 of the tire 1 of this embodiment has a specified orientation for mounting on a vehicle. As a result, the tread portion 2 includes a first tread edge T1 intended to be on the outer side of the vehicle when mounted on the vehicle, and a second tread edge T2 intended to be on the inner side of the vehicle when mounted on the vehicle. However, the tire 1 of the present disclosure is not limited to this configuration.

The first tread edge T1 and the second tread edge T2 each correspond to the edges of the contact patch when the tire 1 is in a normal state and is subjected to 70% of the normal load, with the tread portion 2 in contact with the ground at a flat surface with a camber angle of 0°.

In the case of pneumatic tires for which various standards are established, "normal condition" 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 condition refers to a standard use state according to the tire's intended use, in which the tire is not mounted on a vehicle and is unloaded. Unless otherwise specified, the dimensions of each part of the tire in this specification are values measured in the normal condition.

A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "design rim," and in the case of ETRTO, it is called a "measuring rim."

"Normal internal pressure" is the air pressure specified for each tire by each standard, including the standards on which the tire is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

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

The tread portion 2 includes a plurality of circumferential grooves 3 extending continuously in the tire circumferential direction between the first tread edge T1 and the second tread edge T2, and a plurality of land portions 4 separated by the plurality of circumferential grooves 3. 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 this configuration. In other embodiments of the tire 1 of this disclosure, for example, the tread portion 2 may be a so-called four-rib tire in which the tread portion 2 is composed of three circumferential grooves 3 and four land portions 4.

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. Of the multiple circumferential grooves 3, the first shoulder circumferential groove 5 is located closest to the first tread edge T1. Of the multiple circumferential grooves 3, the second shoulder circumferential groove 6 is located closest to the second tread edge T2. The first crown circumferential groove 7 is located between the first shoulder circumferential groove 5 and the tire equator C. The second crown circumferential groove 8 is located 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, 25% to 35% 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 20% 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 parallel to the tire circumferential direction. For example, each circumferential groove 3 may extend in a wavy pattern.

It is desirable that the groove width W1 of each circumferential groove 3 be at least 3 mm. Furthermore, it is desirable that the groove width W1 of each circumferential groove 3 be 3.0% to 8.0% of the tread width TW. In a more desirable aspect, in this embodiment, of the multiple circumferential grooves 3, the first shoulder circumferential groove 5 has the smallest groove width. However, the present disclosure is not limited to this aspect.

The multiple land portions 4 in this embodiment include a first middle land portion 11 and a second middle land portion 12. The first middle land portion 11 is disposed between the first tread edge T1 and the tire equator C. The first middle land portion 11 in 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 disposed between the second tread edge T2 and the tire equator C. The second middle land portion 12 in this embodiment is divided between the second shoulder circumferential groove 6 and the second crown circumferential groove 8.

The multiple land portions 4 in 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 located axially outward of the first shoulder circumferential groove 5 and includes the first tread edge T1. The second shoulder land portion 14 is located axially outward of the second shoulder circumferential groove 6 and includes the second tread edge T2. The crown land portion 15 is located between the first crown circumferential groove 7 and the second crown circumferential groove 8 and is disposed on the tire equator C.

In the present disclosure, at least one land portion 4 is provided with at least one shallow groove 30 that communicates with the circumferential groove 3. Hereinafter, the land portion 4 provided with the shallow groove 30 may be referred to as the first land portion 61 or the second land portion 62. In this embodiment, the first land portion 61 corresponds to the first middle land portion 11, and the second land portion 62 corresponds to the first shoulder land portion 13.

Figure 2 shows an enlarged view of the first middle land portion 11 and the first shoulder land portion 13. As shown in Figure 2, in this embodiment, multiple shallow grooves 30 are provided in each of the first middle land portion 11 and the first shoulder land portion 13.

Figure 3 shows an enlarged view of the shallow groove 30, and Figure 4 shows a cross-section of the shallow groove 30 taken along line B-B in Figure 2. As shown in Figure 4, the shallow groove 30 has a pair of groove walls 30w that are connected in a V-shape in a cross section perpendicular to its longitudinal direction. The shallow groove 30 has a groove width W6 of 1.5 to 2.5 mm. The pair of groove walls 30w are inclined at an angle θa of 30 to 50° with respect to the tread normal line that is erected at the groove edge of the shallow groove 30. By adopting the above-described configuration, the tire 1 of the present disclosure is able to exhibit excellent wet performance while maintaining wear resistance. The following mechanism is believed to be the reason for this.

The shallow groove 30 of the present disclosure comprises a pair of groove walls 30w connected in a V-shape, and a groove width W6 of 1.5 to 2.5 mm, which prevents excessive reduction in rigidity of the land portion and suppresses distortion of the tread surface of the land portion, thereby suppressing slippage. This allows for wear resistance to be maintained. Meanwhile, by setting the angle θa of the pair of groove walls 30w to 30 to 50°, the groove walls 30w of the shallow groove 30 can come into contact with the ground as the ground pressure acting on the land portion increases, thereby generating large frictional forces on wet roads and demonstrating excellent wet performance. It is believed that this mechanism in the present disclosure allows for excellent wet performance to be achieved while maintaining wear resistance.

The configuration of this embodiment will be described in more detail below. Note that each configuration described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present disclosure can achieve the above-described effects even if it does not include the configurations described below. Furthermore, even if any one of the configurations described below is applied alone to a tire of the present disclosure having the above-described characteristics, improved performance can be expected according to each configuration. Furthermore, when several of the configurations described below are applied in combination, improved composite performance according to each configuration can be expected.

The groove wall 30w in this embodiment is flat. Therefore, in the cross section of the shallow groove 30, the groove wall 30w is configured in a straight line. The groove wall 30w may be, for example, a smoothly curved surface that convexly extends outward from the tire. Also, in Figure 4, the tread surface of the land portion and the groove wall 30w are bent and connected to form a ridgeline, but they may also be connected by a smoothly curved surface. Similarly, in Figure 4, a pair of groove walls 30w are bent and connected to form a ridgeline, but they may also be connected by a smoothly curved surface.

The angle θa of the groove walls 30w is preferably 40 to 50°. The angle θb between a pair of groove walls 30w is preferably 60° or greater, more preferably 80° or greater, even more preferably 85° or greater, and is preferably 100° or less, and even more preferably 95° or less. The depth d1 of the shallow grooves 30 is, for example, 0.5 to 1.5 mm. Such shallow grooves 30 help to improve wear resistance and wet performance in a balanced manner.

As shown in FIG. 2 , the shallow groove 30 of this embodiment includes a first shallow groove 31 provided in the first land portion 61 (in this embodiment, the first middle land portion 11) and a second shallow groove 32 provided in the second land portion 62 (in this embodiment, the first shoulder land portion 13). The first shallow groove 31 extends from the circumferential groove 3 (in this embodiment, the first shoulder circumferential groove 5) between the first land portion 61 and the second land portion 62 to one side in the tire axial direction and has an interrupted end 31a within the first land portion 61. The second shallow groove 32 extends from the circumferential groove 3 to the other side in the tire axial direction and has an interrupted end 32a within the second land portion 62. Such first shallow grooves 31 and second shallow grooves 32 can further enhance the above-mentioned effects.

The first shallow grooves 31 and the second shallow grooves 32 are, for example, inclined in the same direction relative to the tire axial direction. The angle of the first shallow grooves 31 and the second shallow grooves 32 relative to the tire axial direction is, for example, 20° or less, and preferably 3 to 17°. However, the present disclosure is not limited to this embodiment.

From the perspective of improving wet performance, it is desirable that the distance between the first shallow grooves 31 and the second shallow grooves 32 in the tire circumferential direction is small. Therefore, in a plan view of the tread, it is desirable that the imaginary extension region 35 (shown by dots in Figure 2) formed by extending the first shallow groove 31 along its length toward the second land portion 62 overlap with the second shallow groove 32. In a more desirable embodiment, 50% or more of the groove width of the end of the second shallow groove 32 on the circumferential groove 3 side overlaps with the imaginary extension region 35. This further improves wet performance.

As shown in FIG. 3, the first shallow groove 31 includes a portion 46 that extends with a constant groove width. The first shallow groove 31 also includes a portion 47 where the groove width decreases from the portion 46 toward the discontinuous end 31a. Meanwhile, the second shallow groove 32 has a continuously decreasing groove width from the circumferential groove 3 to the discontinuous end 32a. Such first shallow groove 31 and second shallow groove 32 can improve wear resistance and wet performance in a well-balanced manner.

From a similar perspective, the axial length L3 of the first shallow groove 31 is 40% to 50% of the axial width W5 (shown in Figure 2) of the tread surface of the first middle land portion 11. Furthermore, the axial length L8 of the second shallow groove 32 is 15% to 25% of the axial width W9 of the tread surface of the first shoulder land portion 13. In a more desirable embodiment, the length L8 of the second shallow groove 32 is shorter than the length L3 of the first shallow groove 31. Specifically, the length L8 is 50% to 70% of the length L3.

As shown in FIG. 2, the first shoulder land portion 13 is provided with, for example, a plurality of first shoulder lateral grooves 41. In this embodiment, the first shoulder lateral grooves 41 and the second shallow grooves 32 are arranged alternately in the tire circumferential direction.

The first shoulder lateral grooves 41, for example, extend axially inward from at least the first tread edge T1 and terminate within the first shoulder land portion 13. In this embodiment, the first shoulder lateral grooves 41 extend across the first tread edge T1. It is desirable that the angle of the first shoulder lateral grooves 41 relative to the tire axial direction increases axially inward.

The end 41a of the first shoulder lateral groove 41 is preferably located axially inward of the end 32a of the second shallow groove 32. The axial distance L7 from the 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 of the first shoulder land portion 13. Such first shoulder lateral grooves 41 help to improve steering stability and wet performance in a well-balanced manner.

Figure 5 shows a cross-sectional view taken along line D-D in Figure 2. As shown in Figure 5, the first shoulder lateral groove 41 has a chamfered portion 42. 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 is, for example, 35 to 55 degrees. The width W10 and depth d2 of the inclined surface 43 are preferably 0.2 to 0.7 mm. A first shoulder lateral groove 41 having such a chamfered portion 42 can exhibit excellent wear resistance.

As shown in FIG. 2, it is desirable that the width W10 (shown in FIG. 5) of the inclined surface 43 of the chamfered portion 42 of the first shoulder lateral groove 41 increases axially outward around the first tread edge T1. Specifically, at the first tread edge T1, the width W10 of the inclined surface 43 is 20% to 30% of the width of the area excluding the inclined surface 43 of the first shoulder lateral groove 41. Furthermore, at the axially outer end 41b of the first shoulder lateral groove 41, the width W10 of the inclined surface 43 is 45% to 55% of the width of the area excluding the inclined surface 43 of the first shoulder lateral groove 41. As a result, when a large load acts on the tire, such as during cornering, the inclined surface 43 comes into contact with the ground, providing strong grip.

Figure 6 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 Figure 6, the first middle land portion 11 is provided with a plurality of first middle sipes 16 that completely traverse the first middle land portion 11 in the tire axial direction. Similarly, the second middle land portion 12 is provided with a plurality of second middle sipes 17 that completely traverse the second middle land portion 12 in the tire axial direction.

In this specification, "sipe" refers to a small cut in the sipe body, where the width between two sipe walls is 1.5 mm or less. The sipe body also refers to the portion where two sipe walls extend substantially parallel to each other in the tire radial direction. "Substantially parallel" refers to a configuration in which the angle between the two sipe walls is 10 degrees or less. As described below, sipes may include chamfered portions. Sipes may also have a so-called flask bottom, where the width is expanded at the bottom.

Figure 7 shows an enlarged view of the first middle sipe 16. Figure 8 shows an enlarged view of the second middle sipe 17. Figure 9 shows a cross-sectional view of the first middle sipe 16 or the second middle sipe 17 taken along line A-A in Figure 6. As shown in Figures 7 to 9, the first middle sipe 16 and the second middle sipe 17 each include a sipe main body 20 extending in the tire radial direction and a chamfered portion 21 that opens to the tread surface of the tread portion 2 and has a width greater than the width of the sipe main body 20.

As shown in Figure 7, the chamfered portion 21a of the first middle sipe 16 preferably extends axially with a constant chamfer width W2. Furthermore, as shown in Figure 8, the chamfered portion 21b of the second middle sipe 17 preferably has a chamfer width that increases axially from the minimum chamfer width toward both sides. Such first middle sipes 16 and second middle sipes 17 help improve wet and noise performance.

As shown in Figure 9, in the first middle sipe 16 and the second middle sipe 17, the sipe main body 20 extends along the tire radial direction with a constant width, and in a preferred embodiment, extends parallel to the tire radial direction. The width W3 of the sipe main body 20 is, for example, 0.2 to 1.2 mm, and preferably 0.4 to 0.8 mm. The sipe main body 20 may extend in the tire radial direction while oscillating.

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

As shown in Figure 6, the first middle sipes 16 and the second middle sipes 17 are inclined in the same direction relative to the tire axial direction. The angle of the first middle sipes 16 and the second middle sipes 17 relative to the tire axial direction is, for example, 5 to 15 degrees. In a desirable embodiment, the first middle sipes 16 and the second middle sipes 17 are inclined at the same angle relative to the tire axial direction. Such first middle sipes 16 and second middle sipes 17 can improve wet performance while maintaining wear resistance.

As shown in FIG. 7, the chamfered portion 21a of the first middle sipe 16 is disposed 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 that connects to one sipe wall of the sipe main body 20a, and a second inclined surface 27a that connects to the other sipe wall of the sipe main body 20a. In this embodiment, the first inclined surface 26a and the second inclined surface 27a in the first middle sipe 16 have the same size. Furthermore, the chamfer 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 Figure 8, the chamfered portion 21b of the second middle sipe 17 is arranged over the entire length of the second middle sipe 17. Furthermore, the chamfer width of the second middle sipe 17 changes continuously. Such second middle sipes 17 help to suppress uneven wear of the land portion.

The position where the chamfer width of the second middle sipe 17 is smallest is preferably located, for example, in the central region when the second middle land portion 12 is divided into three equal parts in the axial direction of the tire. Such second middle sipes 17 can guide the water film toward the second shoulder circumferential groove 6 and the second crown circumferential groove 8 in a balanced manner when driving on wet roads.

The minimum chamfer width W4a of the chamfered portion 21b of the second middle sipe 17 is, for example, 1.0 to 2.0 mm. In this embodiment, the chamfer width W4a is the same as the chamfer width W2 of the first middle sipe 16. The maximum chamfer 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, and preferably 3.0 times or less, more preferably 2.5 times or less, of the chamfer width W4a. This improves wet performance and noise performance in a balanced manner.

The chamfered portion 21b of the second middle sipe 17 includes a first inclined surface 26b that connects to one sipe wall of the sipe main body 20b and a second inclined surface 27b that connects to the other sipe wall of the sipe main body 20b. In this embodiment, at the end 17b of the chamfered portion 21b of the second middle sipe 17 on the second tread edge T2 side, the width of the first inclined surface 26b is smaller than the width of the second inclined surface 27b. Furthermore, at the end 17a of the chamfered portion 21b of the second middle sipe 17 on the tire equator C side, the width of the first inclined surface 26b is larger than the width of the second inclined surface 27b. In a more desirable embodiment, the width of the inclined surface at the location where the groove wall of the circumferential groove 3 and the sipe wall of the second middle sipe 17 join to form an obtuse-angled corner is larger than the width of the inclined surface at the location where the groove wall and the sipe wall join to form an acute-angled corner. This reduces uneven wear at the ends of the second middle sipes 17.

The first middle sipes 16 and the second middle sipes 17 each extend axially to a constant depth. In this embodiment, the first middle sipes 16 and the second middle sipes 17 have the same depth. Furthermore, the depth of these sipes is preferably, for example, 60% to 80% of the depth of the circumferential grooves 3. This improves wet performance and noise performance in a balanced manner.

As shown in FIG. 6 , the second middle land portion 12 is provided with, for example, at least one semi-open middle sipe 33. One end of the semi-open middle sipe 33 is connected to the second shoulder circumferential groove 6, and the other end terminates within the second middle land portion 12. In this embodiment, the second middle land portion 12 is provided with multiple semi-open middle sipes 33; specifically, the second middle sipes 17 and the semi-open middle sipes 33 are arranged alternately in the tire circumferential direction.

It is desirable that the semi-open middle sipes 33 terminate closer to the second tread edge T2 than the axial center of the second middle sipes 17. The axial length L4 of the semi-open middle sipes 33 is, for example, 35% to 45% of the axial width W7 of the second middle land portion 12. Such semi-open middle sipes 33 can improve wet performance while maintaining steering stability.

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

The semi-open middle sipes 33 extend, for example, from the tread surface to the bottom of the tread portion 2 at a constant width. The depth of the semi-open middle sipes 33 is preferably smaller than the depth of the second middle sipes 17. The depth of the semi-open middle sipes 33 is 20% or less of the maximum depth of the second middle sipes 17, specifically 0.5 to 1.5 mm. Such semi-open middle sipes 33 can provide friction on wet roads while maintaining wear resistance and handling 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 sipes 36 extend from the first crown circumferential grooves 7 and terminate within the crown land portion 15. The second crown sipes 37 extend from the second crown circumferential grooves 8 and terminate within the crown land portion 15. In this embodiment, the crown land portion 15 is provided with the first crown sipes 36 and second crown sipes 37 alternately arranged in the tire circumferential direction. Such first crown sipes 36 and second crown sipes 37 help to improve wet performance and noise performance in a well-balanced manner.

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

The first crown sipes 36 and the second crown sipes 37 each cross the axial center of the crown land portion 15. The axial length L5 of the first crown sipes 36 and the axial length L6 of the second crown sipes 37 are each 55% to 70% of the axial width W8 of the crown land portion 15. In a more desirable embodiment, the length L6 of the second crown sipes 37 is longer than the length L5 of the first crown sipes 36. The length L6 is preferably 103% to 130% of the length L5, and more preferably 103% to 115%. This improves wet performance and makes it easier for the pitch noise of the first crown sipes 36 and the second crown sipes 37 to be converted into white noise.

Figure 10 shows a cross-sectional view taken along line CC in Figure 6. As shown in Figure 10, the first crown sipe 36 includes a first sipe wall 23 and a 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 corner portion in a tread plan view. 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 corner portion in a tread plan view.

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

As shown in Figure 6, it is desirable that the inclined surface 23b of the chamfered portion 21c of the first crown sipe 36 narrows in width, for example, toward the tire equator C. This allows the water film to be actively guided into the first crown circumferential groove 7 when the first crown sipe 36 comes into contact with a wet road surface.

The second crown sipes 37 have substantially the same configuration as the first crown sipes 36. Therefore, the configuration of the first crown sipes 36 described above can be applied to the second crown sipes 37, and further explanation will be omitted here.

Figure 11 shows an enlarged view of the second shoulder land portion 14. As shown in Figure 11, the second shoulder land portion 14 is provided with, for example, multiple second shoulder lateral grooves 51 and multiple shoulder sipes 52.

The second shoulder lateral grooves 51 extend axially inward from at least the second tread edge T2 and terminate within the second shoulder land portion 14. In this embodiment, the second shoulder lateral grooves 51 extend across the second tread edge T2. The axial distance L9 from the end 51a of the second shoulder lateral groove 51 to the second shoulder circumferential groove 6 is, for example, 10% to 20% of the tread width W11 of the second shoulder land portion 14. In a more desirable configuration, the distance L9 is greater than the axial distance L7 (shown in Figure 2) from the end 41a of the first shoulder lateral groove 41 to the first shoulder circumferential groove 5. This achieves a balanced improvement in handling stability and wet performance, while also reducing pitch noise from the first shoulder lateral grooves 41 and second shoulder lateral grooves 51 to white noise, which is expected to improve noise performance.

The second shoulder lateral groove 51 has a chamfered portion 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 further description here will be omitted.

The shoulder sipes 52 extend, for example, from the second shoulder circumferential groove 6 to a position beyond the second tread edge T2. For example, the shoulder sipes 52 extend at a constant width from the tread surface to the bottom of the tread portion 2. The depth of the shoulder sipes 52 is, for example, 0.5 to 1.5 mm. In a more desirable embodiment, the shoulder sipes 52 and the semi-open middle sipes 33 (shown in Figure 6) described above have the same depth. Such shoulder sipes 52 can provide friction on wet roads while maintaining steering stability and wear resistance.

As shown in FIG. 1, the tread portion 2 includes a third land portion 63 located closer to the second tread edge T2 than the tire equator C. In this embodiment, the second shoulder land portion 14 and the second middle land portion 12 correspond to the third land portion 63. These third land portions 63 are not subject to extremely large loads during cornering, so there is little need to increase the contact area during cornering. For this reason, it is desirable for the third land portion 63 to improve edge performance while maintaining circumferential rigidity. From this perspective, in this embodiment, the third land portion 63 is provided with multiple sipes 55 (corresponding to the semi-open middle sipes 33 and shoulder sipes 52 in this embodiment) with a depth of 0.5 to 1.5 mm. This further improves wear resistance and wet performance.

To achieve a good balance between noise performance and wet performance, the land ratio of the tread portion 2 of this embodiment is preferably, for example, 60% to 70%. In this specification, "land ratio" refers to the ratio Sb/Sa of the actual total contact area Sb to the total area Sa of the virtual contact area in which all grooves and sipes are filled.

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

Pneumatic tires of size 245/45R18 having the basic pattern of FIG. 1 were prototyped based on the specifications in Table 1. Furthermore, a tire having the pattern shown in FIG. 12 was prototyped as a comparative example. As shown in FIG. 12, the comparative example tire does not have the shallow grooves described above. Except for the above-mentioned points, the comparative example tire is substantially the same as the example tire. Furthermore, these test tires were tested for wear resistance and wet performance. The common specifications and test methods for each test tire are as follows:
Rim: 18x8.0J
Tire pressure: 230kPa on all wheels
Test vehicle: 2000cc displacement, rear-wheel drive Tire mounting position: all wheels

<Wear resistance>
The test vehicle was driven a certain distance on a public road, and the remaining land height of the first middle land area was measured. The results were expressed as an index, with the remaining land height of the comparative example being set at 100, and a larger index indicates better wear resistance.

<Wet performance>
The above test vehicle was used to measure the coefficient of friction when it entered an asphalt road surface with a depth of 1.0 mm at 65 km/h and braked suddenly. The measurement was carried out three times for each test tire, and the average value of the coefficient of friction was calculated. The results are expressed as an index, with the average value of the coefficient of friction of the comparative example being 100, and the larger the value, the larger the coefficient of friction and the better the wet performance.
The test results are shown in Table 1.

As shown in Table 1, the tires of each example had a wear resistance score of 101 to 103 points, confirming that the tires maintained their wear resistance. This is thought to be because the shallow grooves in the tires of each example suppress slippage on the land tread, maintaining the tires' wear resistance. It can also be confirmed that the tires of each example had significantly improved wet performance scores of 104 to 108 points. In other words, the test results confirmed that the tires of each example exhibited excellent wet performance while maintaining their wear resistance.

[Note]
The present disclosure includes the following aspects.

[Disclosure 1]
A tire having a tread portion,
The tread portion includes a circumferential groove extending continuously in the tire circumferential direction and at least one land portion adjacent to the circumferential groove,
The land portion is provided with at least one shallow groove communicating with the circumferential groove,
The shallow groove has a pair of groove walls that are connected in a V-shape in a cross section perpendicular to the longitudinal direction of the shallow groove,
The shallow groove has a groove width of 1.5 to 2.5 mm,
The pair of groove walls are inclined at an angle of 30 to 50 degrees with respect to a tread normal line extending from the groove edge of the shallow groove.
tire.
[Disclosure 2]
The tire described in Disclosure 1, wherein the shallow groove has a depth of 0.5 to 1.5 mm.
[Disclosure 3]
the at least one land portion includes a first land portion adjacent to one side of the circumferential groove in the tire axial direction and a second land portion adjacent to the other side of the circumferential groove in the tire axial direction,
The tire according to Disclosure 1 or 2, wherein the shallow groove includes a first shallow groove extending from the circumferential groove to the first land portion, and a second shallow groove extending from the circumferential groove to the second land portion.
[Disclosure 4]
The tire according to Disclosure 3, wherein the first shallow groove has a discontinuous end within the first land portion.
[Disclosure 5]
The tire according to Disclosure 3 or 4, wherein the first shallow groove includes a portion extending with a constant groove width.
[Disclosure 6]
The tire according to any one of Disclosures 3 to 5, wherein the second shallow groove has a discontinuous end within the second land portion.
[Disclosure 7]
The tire according to Disclosure 6, wherein the second shallow groove has a groove width that continuously decreases from the circumferential groove to the discontinued end.
[Disclosure 8]
The tire according to any one of Disclosures 3 to 7, wherein, in a plan view of the tread, an imaginary extension region obtained by extending the first shallow groove toward the second land portion along the length direction thereof overlaps with the second shallow groove.
[Disclosure 9]
The tire according to any one of Disclosures 3 to 8, wherein the axial length of the second shallow groove is shorter than the axial length of the first shallow groove.
[Disclosure 10]
The tire according to any one of Disclosures 3 to 9, wherein the circumferential groove is a first shoulder circumferential groove arranged adjacent to a first tread edge.
[Disclosure 11]
The tread portion has a specified orientation for installation on a vehicle,
The tire described in the present disclosure 10, wherein the first tread edge is located on the outer side of the vehicle when mounted on the vehicle.
[Disclosure 12]
the tread portion includes a second tread edge that is located on an inner side of a vehicle when the tire is mounted on the vehicle, and a third land portion that is disposed closer to the second tread edge than the tire equator,
The tire according to the present disclosure 11, wherein the third land portion is provided with a plurality of sipes having a depth of 0.5 to 1.5 mm.

2 tread portion 3 circumferential groove 4 land portion 30 shallow groove 30w groove wall

Claims (11)

A tire having a tread portion,
The tread portion includes a circumferential groove extending continuously in the tire circumferential direction and at least one land portion adjacent to the circumferential groove,
The land portion is provided with at least one shallow groove communicating with the circumferential groove,
The shallow groove has a pair of groove walls that are connected in a V-shape in a cross section perpendicular to the longitudinal direction of the shallow groove,
The shallow groove has a groove width of 1.5 to 2.5 mm,
The pair of groove walls are inclined at an angle of 30 to 50 degrees with respect to a tread normal line that is perpendicular to the groove edge of the shallow groove ,
the at least one land portion includes a first land portion adjacent to one side of the circumferential groove in the tire axial direction and a second land portion adjacent to the other side of the circumferential groove in the tire axial direction,
the circumferential groove is a first shoulder circumferential groove arranged adjacent to a first tread edge ,
The shallow grooves include a first shallow groove extending from the circumferential groove to the first land portion and a second shallow groove extending from the circumferential groove to the second land portion.
tire. The tread portion has a specified orientation for installation on a vehicle,
The tire according to claim 1 , wherein the first tread edge is located on an outer side of the vehicle when mounted on the vehicle . the tread portion includes a second tread edge that is located on an inner side of a vehicle when the tire is mounted on the vehicle, and a third land portion that is disposed closer to the second tread edge than a tire equator,
The tire according to claim 2, wherein the third land portion is provided with a plurality of sipes having a depth of 0.5 to 1.5 mm. The tire according to claim 1 , wherein the first shallow groove has a discontinuous end within the first land portion. The tire according to claim 1 , wherein the first shallow groove includes a portion extending with a constant groove width. The tire according to claim 1 , wherein the second shallow groove has a discontinuous end within the second land portion. The tire according to claim 6 , wherein the second shallow groove has a groove width that continuously decreases from the circumferential groove to the discontinuous end. 8. The tire according to claim 1, wherein, in a plan view of the tread, an imaginary extension region obtained by extending the first shallow groove toward the second land portion along the length direction of the first shallow groove overlaps with the second shallow groove. The tire according to claim 8 , wherein the circumferential groove extends linearly in the tire circumferential direction. The tire according to claim 1 , wherein the axial length of the second shallow groove is smaller than the axial length of the first shallow groove. 11. The tire according to claim 1, wherein the shallow groove has a depth of 0.5 to 1.5 mm.