JP7779109B2 - tire - Google Patents

Description

This disclosure relates to tires.

Patent Document 1 below proposes a tire with semi-open crown sipes on the crown land portion. The crown sipes are expected to improve ride comfort and quietness.

Japanese Patent Application Laid-Open No. 2021-104800

In recent years, vehicles have become quieter, and there is a demand for tires to have even better noise performance. At the same time, there is also a demand for improved wet performance for tires.

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 and noise performance.

The present disclosure relates to a tire having a tread portion, the tread portion including a plurality of circumferential grooves extending continuously in the tire circumferential direction between a first tread edge and a second tread edge, and a plurality of land portions divided by the plurality of circumferential grooves, the plurality of land portions including a crown land portion disposed on the tire equator, the crown land portion including a first longitudinal edge extending in the tire circumferential direction on the side of the first tread edge, a second longitudinal edge extending in the tire circumferential direction on the side of the second tread edge, and a tread surface between the first longitudinal edge and the second longitudinal edge, and the crown land portion including a first longitudinal edge extending in the tire circumferential direction on the side of the second tread edge, the first longitudinal edge extending in the tire circumferential direction on the side of the second tread edge, and the second longitudinal edge extending in the tire circumferential direction on the side of the first longitudinal edge. a tire having a plurality of first crown sipes that communicate with the tread surface and have discontinuous ends within the crown land portion, at least one of the first crown sipes including a chamfered region that opens onto the tread surface via a chamfered portion and a non-chamfered region that opens onto the tread surface without a chamfered portion, the non-chamfered region starting from the discontinuous end and extending over a range of 5% to 20% of the axial length of the first crown sipe, and the chamfered region extending over a range of 80% to 95% of the axial length of the first crown sipe.

By adopting the above-described configuration, the tire disclosed herein is able to exhibit excellent wet performance and noise performance.

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 the crown land portion of FIG. 1 . FIG. 3 is an enlarged view of the first crown sipe and the second crown sipe of FIG. 2 . 3 is a cross-sectional view taken along line AA in FIG. 2. 3 is a cross-sectional view taken along line BB 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 . 3 is a cross-sectional view taken along line CC in FIG. 2. 3 is a cross-sectional view taken along line DD in FIG. 2. FIG. 2 is an enlarged view of a first shoulder land portion of FIG. 1 . 9 is a cross-sectional view taken along line EE in FIG. 8. 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 reference tire. FIG. 4 is an enlarged view of a crown land 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 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.

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 include a crown land portion 15. 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 this embodiment, the multiple land portions 4 include a first middle land portion 11, a second middle land portion 12, a first shoulder land portion 13, and a second shoulder land portion 14. The first middle land portion 11 is located between the first shoulder circumferential groove 5 and the first crown circumferential groove 7. The second middle land portion 12 is located between the second shoulder circumferential groove 6 and the second crown circumferential groove 8. 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.

Figure 2 shows an enlarged view of the crown land portion 15. As shown in Figure 2, the crown land portion 15 includes a first longitudinal edge 15a extending in the tire circumferential direction on the first tread edge T1 side, a second longitudinal edge 15b extending in the tire circumferential direction on the second tread edge T2 side, and a tread surface 15s between the first longitudinal edge 15a and the second longitudinal edge 15b.

The crown land portion 15 is provided with a plurality of first crown sipes 36. The first crown sipes 36 communicate with the first longitudinal edge 15a and have discontinuous ends 36a within the crown land portion 15. In a preferred embodiment, the crown land portion 15 of this embodiment is provided with a plurality of second crown sipes 37. The second crown sipes 37 communicate with the second longitudinal edge 15b and have discontinuous ends 37a within the crown land portion 15.

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 3 shows an enlarged view of the first crown sipes 36 and the second crown sipes 37. As shown in Figure 3, at least one of the first crown sipes 36 includes a chamfered region 31 and a non-chamfered region 32.

Figure 4 shows a cross-sectional view taken along line A-A in Figure 2, illustrating the chamfered region 31. As shown in Figure 4, the chamfered region 31 is an area that opens onto the tread surface 15s via a chamfered portion 38. Figure 5 shows a cross-sectional view taken along line B-B in Figure 2, illustrating the non-chamfered region 32. As shown in Figure 4, the non-chamfered region 32 is an area that opens onto the tread surface 15s without a chamfered portion.

As shown in FIG. 3, the non-chamfered region 32 begins at the discontinuous end 36a of the first crown sipe 36 and extends in a range of 5% to 20% of the axial length L5 (shown in FIG. 2) of the first crown sipe 36. The chamfered region 31 extends in a range of 80% to 95% of the axial length L5 of the first crown sipe 36. By adopting the above-described configuration, the tire 1 of the present disclosure is able to exhibit excellent wet performance and noise performance. The following mechanism is believed to be the reason for this.

The first crown sipes 36 can provide friction when driving on wet roads. On the other hand, because the first crown sipes 36 have discontinuous ends 36a within the crown land portion 15, pitch noise can be expected to be reduced compared to full-open sipes.

As described above, the first crown sipe 36 includes a chamfered region 31 and a non-chamfered region 32. The chamfered region 31 helps reduce noise when the tread surface 15s makes contact with the ground. Meanwhile, the non-chamfered region 32 allows the sipe edge to provide greater friction, helping to improve wet performance. The developers also discovered that by positioning the non-chamfered region 32 so that it begins at the end of the sipe, wet performance can be significantly improved even if the length of the non-chamfered region 32 is relatively short. This is thought to be because the amount of deformation of the sipe is small near the end, and greater friction is exerted when the non-chamfered region 32 is located.

Based on the above findings, in the present disclosure, the non-chamfered region 32 is formed in a range of 5% to 20% of the length L5 of the first crown sipe 36, and the chamfered region 31 is formed in a range of 80% to 95% of the length L5 of the first crown sipe 36. This allows for a balanced improvement in wet performance and noise performance. It is believed that this mechanism in the present disclosure enables excellent wet performance and noise performance to be achieved.

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.

As shown in FIG. 2, the crown land portion 15 of this embodiment is provided with multiple first crown sipes 36 as described above. Furthermore, the first crown sipes 36 are inclined, for example, at an angle of 10 to 20 degrees relative to the tire axial direction. This ensures improved wet and noise performance. The first crown sipes 36 cross the axial center position of the crown land portion 15 and, in a preferred embodiment, also cross the tire equator C. The axial length L5 of the first crown sipes 36 is, for example, 55% to 70% of the axial width W8 of the crown land portion 15. This ensures that the first crown sipes 36 have sufficient length, enabling improved wet performance.

As shown in Figure 5, the non-chamfered region 32 has a sipe main body 40 with a constant width W12 that extends along the tire radial direction and opens at the tread surface 15s. In this embodiment, the sipe main body 40 extends parallel to the tire radial direction, but it may also extend in the tire radial direction while oscillating. The width W12 of the sipe main body 40 is, for example, 0.2 to 1.2 mm, and preferably 0.4 to 0.8 mm.

As shown in Figure 3, the axial length L11 of the non-chamfered region 32 is preferably 5% to 15% of the length L5 (shown in Figure 2) of the first crown sipe 36, and more preferably 6% to 10%. This improves wet performance and noise performance in a balanced manner.

As shown in FIG. 4, the chamfered region 31 includes a sipe main body 40 extending in the tire radial direction and a chamfered portion 38 that opens onto the tread surface 15s with a width greater than that of the sipe main body 40. The chamfered portion 38 includes an inclined surface 39 between the sipe main body 40 and the tread surface 15s. In this embodiment, the chamfered portion 38 has the inclined surface 39 formed on only one side of each of the two sipe edges. For example, the chamfered portion 38 may have the inclined surface 39 formed on both sides of each of the two sipe edges.

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 is continuous with 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 is continuous with 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 body surface 23a that constitutes the sipe main body portion 20c and an inclined surface 39 that constitutes the chamfered portion 38. The angle θ3 of the inclined surface 39 with respect to the tire normal is, for example, 55 to 65°. The second sipe wall 24 is connected to the tread surface 15s of the crown land portion 15 without being chamfered. A first crown sipe 36 with such a chamfered portion 38 can improve wet performance and wear resistance in a well-balanced manner.

As shown in Figure 3, it is desirable for the chamfer width of the chamfered portion 38 of the first crown sipe 36 to increase continuously toward the first tread edge T1. 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 axial length L12 of the chamfered region 31 of the first crown sipe 36 is preferably 85% to 95% of the length L5 (shown in Figure 2) of the first crown sipe 36, and more preferably 90% to 94%.

The second crown sipes 37 cross the axial center of the tread surface 15s of the crown land portion 15, and preferably cross the tire equator C. Furthermore, the discontinuous ends 37a of the second crown sipes 37 are located closer to the first tread edge T1 than the discontinuous ends 36a of the first crown sipes 36. This allows the first crown sipes 36 and second crown sipes 37 to provide a large frictional force when driving on wet roads.

As shown in FIG. 2, the axial length L6 of the second crown sipes 37 is 55% to 70% of the width W8 of the tread surface 15s of the crown land portion 15. In a more desirable embodiment, the axial length L6 of the second crown sipes 37 is greater than the axial 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 noise performance in a balanced manner.

The second crown sipes 37 have substantially the same configuration as the first crown sipes 36, except for the configuration described above. Therefore, the configuration of the first crown sipes 36 described above can be applied to the second crown sipes 37.

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. 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.

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 C-C 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 extends axially with a constant chamfer width W2. Also, as shown in Figure 8, the chamfered portion 21b of the second middle sipe 17 increases in chamfer width from the minimum chamfer width toward both sides in the axial direction of the tire. 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 FIG. 6 , the first middle sipes 16 and the second middle sipes 17 are inclined in the same direction relative to the tire axial direction. In a more desirable configuration, the first middle sipes 16 and the second middle sipes 17 are inclined in the same direction relative to the tire axial direction as the first crown sipes 36 and the second crown sipes 37, and in a desirable configuration, are inclined at a slightly smaller angle relative to the tire axial direction than the first crown sipes 36 and the second crown sipes 37. This sipe arrangement helps to turn the impact sound made when the sipe edges contact the ground into white noise. 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 configuration, 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 the 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 , it is desirable to provide, for example, multiple middle shallow grooves 30 in the first middle land portion 11. In this embodiment, the first middle sipes 16 and the middle shallow grooves 30 are arranged alternately in the circumferential direction of the tire. The middle shallow grooves 30 extend, for example, from the first shoulder circumferential groove 5 and terminate within the first middle land portion 11. The middle shallow grooves 30 terminate closer to the first tread edge T1 than the axial center of the first middle land portion 11. The axial length L3 of the middle shallow grooves 30 is, for example, 35% to 50% of the axial width W5 of the first middle land portion 11. Such middle shallow grooves 30 improve wet performance and handling stability on dry roads (hereinafter sometimes simply referred to as "handling stability") in a balanced manner.

The middle shallow grooves 30 are inclined, for example, in the same direction as the first middle sipes 16 relative to the tire axial direction. The angle of the middle shallow grooves 30 relative to the tire axial direction is, for example, 5 to 15 degrees. In a more desirable embodiment, the difference in angle between the first middle sipes 16 and the middle shallow grooves 30 is 5 degrees or less. This improves wet performance and noise performance while maintaining wear resistance.

Figure 10 shows a cross-sectional view taken along line D-D in Figure 6. As shown in Figure 10, the groove depth d1 of the middle shallow groove 30 is, for example, 0.5 to 1.5 mm. The groove width W6 of the middle shallow groove 30 is, for example, 1.5 to 2.5 mm. In a more desirable embodiment, the middle shallow groove 30 has a V-shaped cross-section formed by two groove walls 30a that are inclined relative to the tire radial direction. The angle θ2 of the groove wall 30a relative to the tire normal is, for example, 30 to 50 degrees. When cornering on a wet road, for example, the groove wall 30a comes into contact with the ground as the land portion deforms due to increased ground pressure, improving wet performance.

As shown in FIG. 6 , the second middle land portion 12 is provided with, for example, multiple semi-open middle sipes 33. One end of each 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 sipes 17 and semi-open middle sipes 33 are arranged alternately in the tire circumferential direction in the second middle land portion 12.

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.

Figure 11 shows an enlarged view of the first shoulder land portion 13. As shown in Figure 11, the first shoulder land portion 13 is provided with, for example, multiple first shoulder lateral grooves 41 and multiple shoulder shallow grooves 45.

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. The angle of the first shoulder lateral grooves 41 relative to the tire axial direction desirably increases axially inward. The axial distance L7 from the terminated end 41a of the first shoulder lateral groove 41 to the first shoulder circumferential groove 5 is 3% to 10% of the tread width W9 of the first shoulder land portion 13. Such first shoulder lateral grooves 41 help to improve handling stability and wet performance in a well-balanced manner.

Figure 12 shows a cross-sectional view taken along line E-E in Figure 11. As shown in Figure 12, 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. 11, it is desirable that the width W10 (shown in FIG. 12) 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.

The shoulder shallow groove 45 extends, for example, from the first shoulder circumferential groove 5 and terminates within the first shoulder land portion 13. In this embodiment, the shoulder shallow groove 45 extends, for example, beyond the terminated end 41a of the first shoulder lateral groove 41 toward the first tread edge T1. Furthermore, the axial length L8 of the shoulder shallow groove 45 is desirably shorter than the axial length L3 (shown in FIG. 6) of the middle shallow groove 30. Specifically, the length L8 of the shoulder shallow groove 45 is 50% to 80% of the length L3 of the middle shallow groove 30. Such shoulder shallow grooves 45 help 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 above-described middle shallow groove 30. Therefore, the cross-sectional configuration of the above-described middle shallow groove 30 can be applied to the shoulder shallow groove 45. Furthermore, the width and depth of the shoulder shallow groove 45 decrease toward the first tread edge T1. This improves wear resistance and handling stability.

Figure 13 shows an enlarged view of the second shoulder land portion 14. As shown in Figure 13, 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 FIG. 11) 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 53 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 explanation will be omitted here.

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.

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%, as shown in Figure 1. 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.

A pneumatic tire of size 245/45R18 having the basic pattern of Figure 1 was prototyped based on the specifications in Table 1. Additionally, a tire having the pattern shown in Figure 14 was prototyped as a reference tire (reference tire) for comparing noise performance. As shown in Figure 14, this reference tire, compared to the pattern shown in Figure 1, has first shoulder lateral grooves a and second shoulder lateral grooves b that communicate with circumferential grooves, does not have middle shallow grooves or shoulder shallow grooves, and does not have chamfered sipes.

Furthermore, as Comparative Example 1, a prototype tire was manufactured having the crown land portion c shown in FIG. 15. As shown in FIG. 15, in the tire of Comparative Example 1, the first crown sipe d and the second crown sipe e are each entirely configured with a chamfered region. Furthermore, the chamfered portion of each sipe extends at a constant width. As Comparative Examples 2 and 3, prototype tires were manufactured in which the range of the non-chamfered region was outside the range of the present disclosure. Except for the above-mentioned features, the tires of Comparative Examples 1 to 3 were substantially the same as the tires of the Example. Furthermore, wet performance and noise performance were tested for these test tires. 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

<Wet performance>
The wet performance of the test vehicle when driven on a wet road surface was evaluated by the driver. The results are expressed as a score, with the wet performance of the comparative example being 100, and the higher the score, the better the wet performance.

<Noise performance>
The test vehicle was driven on a dry road at a speed of 40 to 100 km/h, and the maximum sound pressure inside the vehicle was measured. The results are expressed as an index where the reduction in sound pressure, which is the difference from the sound pressure of the reference tire, is set to 100 for the reduction in sound pressure of the comparative tire. The larger this index, the smaller the maximum sound pressure of the noise, indicating excellent noise performance.
The test results are shown in Table 1.

As shown in Table 1, it can be seen that Examples 1 to 7 have better wet performance and noise performance than the Comparative Example. Furthermore, in Examples 1 to 7, wet performance was 106 to 112 points, and noise performance was 110 to 115 points, demonstrating significant improvements in wet performance and noise performance. In contrast, in Comparative Examples 2 and 3, either wet performance or noise performance was impaired. As can be seen from the test results above, it was confirmed that the tires of the Examples exhibit excellent wet performance and noise performance.

[Note]
The present disclosure includes the following aspects.

[Disclosure 1]
A tire having a tread portion,
the tread portion includes a plurality of circumferential grooves extending continuously in the tire circumferential direction between a first tread edge and a second tread edge, and a plurality of land portions separated by the plurality of circumferential grooves,
the plurality of land portions include a crown land portion disposed on the tire equator,
the crown land portion includes a first longitudinal edge extending in the tire circumferential direction on the first tread end side, a second longitudinal edge extending in the tire circumferential direction on the second tread end side, and a tread surface between the first longitudinal edge and the second longitudinal edge,
a plurality of first crown sipes are provided in the crown land portion, the first sipes being connected to the first longitudinal edge and having discontinuous ends within the crown land portion;
At least one of the first crown sipes includes a chamfered region that opens to the tread surface via a chamfered portion and a non-chamfered region that opens to the tread surface without passing through a chamfered portion,
the non-chamfered region starts from the interrupted end and is formed in a range of 5% to 20% of the length of the first crown sipe in the tire axial direction,
The chamfered region is formed in a range of 80% to 95% of the length of the first crown sipe in the tire axial direction.
tire.
[Disclosure 2]
The tire described in Disclosure 1, wherein the non-chamfered region is formed in a range of 6% to 10% of the length of the first crown sipe.
[Disclosure 3]
The tread portion has a specified orientation for installation on a vehicle,
The tire according to Disclosure 1 or 2, wherein the first tread edge is located on an outer side of the vehicle when mounted on the vehicle.
[Disclosure 4]
The tire according to any one of Disclosures 1 to 3, wherein a chamfer width of the chamfered portion increases continuously toward the first tread edge side.
[Disclosure 5]
The tire according to any one of claims 1 to 4, wherein the first crown sipe crosses the tire equator.
[Disclosure 6]
a plurality of second crown sipes are provided in the crown land portion, the second crown sipes being connected to the second longitudinal edge and having discontinuous ends within the crown land portion;
The tire according to any one of Disclosures 1 to 5, wherein the axial length of the second crown sipes is greater than the axial length of the first crown sipes.
[Disclosure 7]
The tire of this disclosure 6, wherein the second crown sipe crosses the tire equator.
[Disclosure 8]
The tire according to Disclosure 6 or 7, wherein the interrupted end of the second crown sipe is located closer to the first tread edge than the interrupted end of the first crown sipe.

2 tread portion 3 circumferential groove 4 land portion 15 crown land portion 31 chamfered region 32 non-chamfered region 36 first crown sipe 38 chamfered portion T1 first tread edge T2 second tread edge

Claims (7)

A tire having a tread portion,
the tread portion includes a plurality of circumferential grooves extending continuously in the tire circumferential direction between a first tread edge and a second tread edge, and a plurality of land portions separated by the plurality of circumferential grooves,
the plurality of land portions include a crown land portion disposed on the tire equator,
the crown land portion includes a first longitudinal edge extending in the tire circumferential direction on the first tread end side, a second longitudinal edge extending in the tire circumferential direction on the second tread end side, and a tread surface between the first longitudinal edge and the second longitudinal edge,
a plurality of first crown sipes are provided in the crown land portion, the first sipes being connected to the first longitudinal edge and having discontinuous ends within the crown land portion;
At least one of the first crown sipes includes a chamfered region that opens to the tread surface via a chamfered portion and a non-chamfered region that opens to the tread surface without passing through a chamfered portion,
the non-chamfered region starts from the interrupted end and is formed in a range of 5% to 20% of the length of the first crown sipe in the tire axial direction,
the chamfered region is formed in a range of 80% to 95% of the length of the first crown sipe in the tire axial direction,
a plurality of second crown sipes are provided in the crown land portion, the second crown sipes being connected to the second longitudinal edge and having discontinuous ends within the crown land portion;
The length of the second crown sipe in the tire axial direction is greater than the length of the first crown sipe in the tire axial direction,
The second crown sipe crosses the tire equator .
tire. The tire according to claim 1 , wherein the discontinued end of the second crown sipe is located closer to the first tread edge than the discontinued end of the first crown sipe . The tire according to claim 1 or 2 , wherein the non-chamfered region is formed in a range of 6% to 10% of the length of the first crown sipe . 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 tire according to claim 1 , wherein a chamfer width of the chamfered portion increases continuously toward the first tread edge . 6. The tire of claim 1, wherein the first crown sipe traverses the tire equator . the crown land portion is divided between a first crown circumferential groove and a second crown circumferential groove,
the first crown sipe includes a first sipe wall and a second sipe wall,
the first sipe wall is a sipe wall that is continuous with a groove wall of the first crown circumferential groove and forms an obtuse angled corner portion in a tread plan view,
the second sipe wall is a sipe wall that is continuous with a groove wall of the first crown circumferential groove and forms an acute corner portion in a tread plan view,
The first sipe wall includes an inclined surface that constitutes the chamfered portion,
The tire according to claim 1 , wherein the second sipe wall is connected to the tread surface of the crown land portion without being chamfered.