tire

Abstract

To provide a tire that can exert excellent on-snow performance, while maintaining steering stability on a dry road surface.SOLUTION: A tire has a tread part 2. The tread part 2 includes a first tread end T1, a second tread end T2, a crown land part 15 provided between the first tread end T1 and the second tread end T2, and a first crown circumferential groove 7 continuously extending in a tire circumferential direction adjacently to the first tread end T1 of the crown land part 15. In a groove bottom part of the first crown circumferential groove 7 are formed a plurality of protrusion parts 20 protruding in a tire radial direction. In the crown land part 15 is not formed a groove whose groove width is over 2.0 mm and in which a depth of a portion whose groove width is over 2.0 mm exceeds 2.0 mm but is formed a sipe 25.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to tires. [Background technology]

[0002] Patent Document 1 below proposes a tire with multiple protrusions formed at the bottom of the main grooves that extend continuously in the tire circumferential direction. This tire is expected to improve traction and braking performance on snow by forming snow pillars in the main grooves when driving on snow and having the protrusions dig into the snow pillars. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-196281 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the demand for snow performance from tires has been increasing. At the same time, sufficient consideration must also be given to the handling stability of tires on dry roads.

[0005] The present disclosure has been devised in view of the above-described circumstances, and has as its main object to provide a tire that can exhibit excellent performance on snow while maintaining steering stability on dry roads. [Means for solving the problem]

[0006] The present disclosure relates to a tire having a tread portion, the tread portion including a first tread edge, a second tread edge, a crown land portion provided between the first tread edge and the second tread edge, and a first crown circumferential groove extending continuously in the tire circumferential direction adjacent to the first tread edge side of the crown land portion, wherein a groove bottom of the first crown circumferential groove is formed with a plurality of protrusions protruding in the tire radial direction, the crown land portion is not provided with a drainage groove whose opening width at the tread surface exceeds 2.0 mm and whose depth in an area where the distance between two groove walls exceeds 2.0 mm exceeds 2.0 mm, and the crown land portion is provided with sipes. [Effects of the Invention]

[0007] By adopting the above-described configuration, the tire of the present disclosure can exhibit excellent performance on snow while maintaining steering stability on dry road surfaces. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a development view of a tread portion showing an embodiment of the present disclosure. FIG. [Figure 2] 2 is an enlarged view of a crown land portion, a first middle land portion, and a first crown circumferential groove in FIG. 1. [Figure 3] FIG. 4 is an enlarged perspective view of a first crown circumferential groove. [Figure 4] FIG. [Figure 5] 3 is an enlarged view of the first crown sipe, the second crown sipe, the third crown sipe, and the fourth crown sipe in FIG. 2. [Figure 6] FIG. 6 is a cross-sectional view taken along line AA in FIG. 5. [Figure 7] FIG. 3 is a cross-sectional view taken along line BB in FIG. 2. [Figure 8] FIG. 3 is a cross-sectional view taken along line CC in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present disclosure will be described below with reference to the drawings. Fig. 1 is a development view of a tread portion 2 of a tire 1 showing an embodiment of the present disclosure. The tire 1 of this embodiment is, for example, a winter tire, and is suitably used as a pneumatic tire for passenger cars. 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 are not filled with pressurized air inside the tire.

[0010] 1 , the tread portion 2 of the present disclosure includes a first tread edge T1, a second tread edge T2, 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 these circumferential grooves 3. As a desirable aspect, the tire 1 of the present embodiment is configured as a so-called five-rib tire in which the tread portion 2 is configured with four circumferential grooves 3 and five land portions 4.

[0011] The tread portion 2 of this embodiment has, for example, a specified orientation for mounting on a vehicle. As a result, the first tread edge T1 is intended to be located on the outer side of the vehicle when mounted on the vehicle. The second tread edge T2 is intended to be located on the inner side of the vehicle when mounted on the vehicle. The orientation for mounting on the vehicle is indicated, for example, by letters or symbols on the sidewall portion (not shown). However, the tire 1 of the present disclosure is not limited to this embodiment, and the orientation for mounting on a vehicle may not be specified.

[0012] The first tread edge T1 and the second tread edge T2 each correspond to the edge of the contact patch when 70% of the normal load is applied to the tire 1 in its normal state and the tread portion 2 is brought into contact with a flat surface at a camber angle of 0°.

[0013] "Normal condition" refers to a state in which, in the case of a pneumatic tire for which various standards are established, the tire is mounted on a normal rim, inflated to the normal internal pressure, and no load is applied. In the case of a tire for which various standards are not established or a non-pneumatic tire, the normal condition refers to a standard use state according to the intended use of the tire, and a state in which no load is applied. Unless otherwise specified in this specification, the dimensions of each part of the tire are values ​​measured in the normal condition. Furthermore, unless otherwise specified in this specification, known methods can be used as appropriate to measure the dimensions and material composition.

[0014] 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."

[0015] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard 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."

[0016] 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 standard 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.

[0017] The circumferential grooves 3 include a first crown circumferential groove 7. The first crown circumferential groove 7 is provided on the first tread edge T1 side of the tire equator C. Furthermore, the circumferential grooves 3 of this embodiment include a second crown circumferential groove 8, a first shoulder circumferential groove 5, and a second shoulder circumferential groove 6. The second crown circumferential groove 8 is provided on the second tread edge T2 side of the tire equator C. The first shoulder circumferential groove 5 is provided between the first crown circumferential groove 7 and the first tread edge T1. The second shoulder circumferential groove 6 is provided between the second crown circumferential groove 8 and Second tread edge T2 It is set between.

[0018] The axial distance L1 from the tire equator C to the groove center line 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 center line of the first crown circumferential groove 7 or the second crown circumferential groove 8 is preferably, for example, 5% to 15% of the tread width TW. The tread width TW is the axial distance from the first tread edge T1 to the second tread edge T2 in the normal state.

[0019] In this embodiment, the first crown circumferential groove 7, the second crown circumferential groove 8, and the second shoulder circumferential groove 6 are arranged in straight lines parallel to the tire circumferential direction. Condition On the other hand, the first shoulder circumferential groove 5 has a groove edge on the tire equator C side that extends in a zigzag shape. However, each circumferential groove 3 is not limited to this shape.

[0020] The groove width W1 of each circumferential groove 3 is preferably at least 3 mm or more. The groove width W1 of each circumferential groove 3 is preferably, for example, 3.0% to 7.0% of the tread width TW. The depth of each circumferential groove 3 is, for example, 5 to 10 mm in the case of a pneumatic tire for a passenger car.

[0021] The land portion 4 of the present disclosure includes a crown land portion 15. The crown land portion 15 is divided between the first crown circumferential groove 7 and the second crown circumferential groove 8, and is provided on the tire equator C in this embodiment. As a result, the first crown circumferential groove 7 is adjacent to the first tread edge T1 side of the crown land portion 15. Furthermore, the land portion 4 of this embodiment includes a first middle land portion 13, a second middle land portion 14, a first shoulder land portion 11, and a second shoulder land portion 12. The first middle land portion 13 is divided between the first shoulder circumferential groove 5 and the first crown circumferential groove 7. The second middle land portion 14 is divided between the second shoulder circumferential groove 6 and the second crown circumferential groove 8. The first shoulder land portion 11 includes the first tread edge T1 and is divided axially outward of the first shoulder circumferential groove 5. The second shoulder land portion 12 includes the second tread edge T2 and is divided axially outward of the second shoulder circumferential groove 6.

[0022] FIG. 2 shows an enlarged view of the crown land portion 15, the first middle land portion 13, and the first crown circumferential groove 7. FIG. 3 shows an enlarged perspective view of a groove bottom 7d of the first crown circumferential groove 7. As shown in FIGS. 2 and 3, a plurality of protrusions 20 protruding in the tire radial direction are formed on the groove bottom 7d of the first crown circumferential groove 7. Note that while FIG. 2 conceptually shows the outlines of the protrusions 20 observable in a plan view of the tread with solid lines, these are omitted in FIG. 1. The specific configuration of the protrusions 20 will be described later.

[0023] As shown in Fig. 2, no drainage grooves are provided in the crown land portion 15. A drainage groove is a groove that can provide substantial drainage, and refers to a groove that has an opening width at the tread surface of more than 2.0 mm and a depth (length in the tire radial direction) of a region where the distance between two groove walls exceeds 2.0 mm. On the other hand, sipes 25 are provided in the crown land portion 15.

[0024] In this specification, the term "sipe" refers to a groove-like body (a recess having a longitudinal direction, including grooves and sipes) having a small width, the width between the two inner walls of the main body being 1.5 mm or less. The main body refers to the portion where the two inner walls extend substantially parallel to each other in the tire radial direction. In a desirable embodiment, the width of the main body of the sipe is, for example, 0.5 to 1.0 mm. As described later, the sipe may include a chamfered portion. The sipe may also have a so-called flask bottom, the width of which is expanded at the bottom.

[0025] By adopting the above-described configuration, the tire of the present disclosure can exhibit excellent performance on snow while maintaining steering stability on dry roads (hereinafter, sometimes simply referred to as "steering stability"). The following mechanism is presumed to be the reason for this.

[0026] When driving on snow, the tire 1 of the present disclosure can exert a large reaction force by causing the protrusions 20 to dig into the snow pillars formed in the first crown circumferential groove 7, thereby providing excellent traction and braking performance on snow.

[0027] On the other hand, the crown land portion 15 does not have the drainage grooves described above. As a result, the crown land portion 15 has high rigidity, and when the crown land portion 15 touches down on a snowy road, it can strongly compact the snow pillars in the first crown circumferential grooves 7 adjacent to the crown land portion 15, further increasing the reaction force described above. In addition, such a crown land portion 15 helps maintain steering stability on dry roads. On the other hand, the crown land portion 15 is provided with sipes 25, which improve performance on snow. Due to this mechanism, the tire 1 of the present disclosure can exhibit excellent performance on snow while maintaining steering stability.

[0028] The following describes the configuration of this embodiment in more detail. 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, performance improvement corresponding to each configuration can be expected. Furthermore, when several of the configurations described below are applied in combination, combined performance improvement corresponding to each configuration can be expected.

[0029] As shown in FIG. 2 , the first crown circumferential groove 7 includes a first groove wall 7a and a second groove wall 7b. The first groove wall 7a is the groove wall on the crown land portion 15 side, and the second groove wall 7b is the groove wall on the first middle land portion 13 side. The protrusions 20 include first protrusions 21 arranged on the first groove wall 7a side and second protrusions 22 arranged on the second groove wall 7b side. The first protrusions 21 and the second protrusions 22 have substantially the same configuration except for their orientations. The multiple first protrusions 21 are arranged at a constant pitch in the tire circumferential direction. Similarly, the multiple second protrusions 22 are arranged at a constant pitch in the tire circumferential direction.

[0030] The protrusions 20 are elongated and have a maximum width W3 in the tire axial direction and a length L3 in the tire circumferential direction that is greater than the width W3. The axial width W3 of one protrusion 20 is, for example, 30% to 70% of the maximum groove width W2 of the first crown circumferential groove 7. When the first protrusions 21 and the second protrusions 22 are configured in the first crown circumferential groove 7 as in this embodiment, the width W3 of one protrusion 20 is 30% to 50% of the groove width W2, and preferably 40% to 50%.

[0031] The length L3 of one protrusion 20 is, for example, 40% to 60% of the circumferential pitch P1 of the protrusions 20. The circumferential length L3 of one protrusion 20 is, for example, 2.0 to 4.0 times the circumferential width W3 of the protrusion 20. Such a protrusion 20 has sufficient rigidity in the circumferential direction of the tire, and can provide a large reaction force when shearing snow pillars in the first crown circumferential groove 7 when traveling on snow. However, the protrusions 20 are not limited to this form.

[0032] Fig. 4 shows an enlarged cross-sectional view of the protrusion 20 along the longitudinal direction of the first crown circumferential groove 7. As shown in Fig. 4, the maximum height h1 of the protrusion 20 in the tire radial direction is, for example, 20% or less of the maximum depth d1 of the first crown circumferential groove 7, and desirably 10% to 20% of the depth d1. Such a protrusion 20 can exhibit the above-mentioned effects while maintaining the drainage performance of the first crown circumferential groove 7.

[0033] The protrusion 20 includes a first surface 31 facing one side in the tire circumferential direction and extending in the tire radial direction, and a second surface 32 disposed on the opposite side to the first surface 31. The angle θ1 of the first surface 31 with respect to the tire radial direction is, for example, 15° or less, preferably 10° or less. The second surface 32 is connected to the first surface 31 via a ridgeline 35 and extends from the ridgeline 35 toward the groove bottom 7d of the first crown circumferential groove 7 at a gentle incline. In this embodiment, the second surface 32 is slightly curved, for example, so as to be convex toward the tire radial outward, but may also be configured as a flat surface. In this specification, the term "ridgeline" refers to a connecting portion formed by connecting two surfaces extending in different directions and having a longitudinal direction. In addition, in this specification, the term "ridgeline" also includes a portion that forms a slightly curved surface in its cross section and has a substantial width.

[0034] The second surface 32 has a larger angle with respect to the tire radial direction than the first surface 31. The angle θ2 of the second surface 32 with respect to the tire radial direction at the outer end of the second surface 32 on the groove bottom 7d side is, for example, 70° or more, and preferably 78 to 86°. The protrusion 20 including such first surface 31 and second surface 32 can generate a large reaction force when the first surface 31 pushes away snow pillars during driving on snow.

[0035] 2 and 3, the protrusions 20 include tapered portions 23 whose axial width decreases toward one side in the tire circumferential direction. This prevents the protrusions 20 from reducing the groove volume of the first crown circumferential grooves 7, thereby maintaining wet performance. When running on dry roads, the air passing through the first crown circumferential grooves 7 is disturbed by the first surface 31, and the tapered portions 23 promote movement of the air in the tire circumferential direction. This action prevents the generation of standing waves in the first crown circumferential grooves 7, helping to reduce air column resonance noise.

[0036] As shown in FIG. 2 , in a plan view of the tread, the tapered portion 23 is formed between a first side surface 33 extending along the tire circumferential direction and a second side surface 34 inclined at a larger angle with respect to the tire circumferential direction than the first side surface 33. The first side surface 33 and the second side surface 34 are connected to the second surface 32 via a ridgeline and extend in the tire radial direction, for example. The first side surface 33 and the second side surface 34 are also connected to the first surface 31 via a ridgeline extending in the tire radial direction. In this embodiment, the first side surface 33 is provided closer to the groove centerline of the first crown circumferential groove 7 than the second side surface 34. This makes it difficult for the region of the first surface 31 on the groove centerline side to deform in the tire circumferential direction, thereby further improving the above-mentioned effects.

[0037] The angle θ3 between the first side surface 33 and the second side surface 34 in a plan view of the tread is, for example, 30° or less, and preferably 15 to 25°. The first side surface 33 and the second side surface 34 arranged at such an angle not only improve on-snow performance but also help to improve wet performance and noise performance in a balanced manner. The angle θ3 is defined, for example, as the maximum angle between the ridgeline formed between the first side surface 33 and the second surface 32 and the ridgeline formed between the second side surface 34 and the second surface 32.

[0038] As shown in Fig. 3, the first protrusions 21 and the second protrusions 22 are oriented in opposite directions in the tire circumferential direction. As a result, the width of the tapered portion 23 of each of the multiple first protrusions 21 decreases toward the first side R1 in the tire circumferential direction. Therefore, the first surface 31 of each first protrusion 21 faces the second side R2, which is opposite the first side R1 in the tire circumferential direction. The second surface 32 of each first protrusion 21 is continuous with the first side R1 of the first surface 31.

[0039] On the other hand, the width of the tapered portion 23 of each of the multiple second protrusions 22 decreases toward the second side R2. Therefore, the first surface 31 of the second protrusion 22 faces the first side R1. The second surface 32 of the second protrusion 22 is continuous with the second side R2 of the first surface 31. With this arrangement of the first protrusions 21 and the second protrusions 22, when the protrusions 20 shear packed snow pillars in the first crown circumferential groove 7 in the tire circumferential direction during driving on snow, the first protrusions 21 can provide a large reaction force to one side in the tire circumferential direction, and the second protrusions 22 can provide a large reaction force to the other side in the tire circumferential direction. This results in a balanced improvement in traction performance and braking performance on snow.

[0040] In a preferred embodiment, the first protrusions 21 and the second protrusions 22 are desirably misaligned in the tire circumferential direction. Specifically, as shown in Fig. 2, in a plan view of the tread, the overlap length between an imaginary area formed by extending the first protrusions 21 parallel to the tire axial direction and the second protrusions 22 is 20% or less, more desirably 10% or less, of the tire circumferential length of the second protrusions 22. In an even more preferred embodiment, the imaginary area does not overlap the second protrusions 22. Such an arrangement of the protrusions 20 can prevent snow from clogging the first crown circumferential grooves 7 when driving on snow, helping to maintain excellent on-snow performance.

[0041] In this embodiment, the above-mentioned protrusions 20 are provided only in the first crown circumferential groove 7. That is, it is desirable that the groove bottom of the second crown circumferential groove 8 (shown in FIG. 1) is flat and not provided with the above-mentioned protrusions 20. Similarly, it is desirable that the groove bottoms of the first shoulder circumferential groove 5 and the second shoulder circumferential groove 6 (shown in FIG. 1) are flat and not provided with the above-mentioned protrusions 20. This can improve wet performance. However, the present disclosure is not limited to this embodiment, and from the viewpoint of further improving on-snow performance, the above-mentioned protrusions 20 may be provided in circumferential grooves 3 other than the first crown circumferential groove 7.

[0042] As shown in FIG. 2, the sipes 25 provided in the crown land portion 15 (hereinafter sometimes referred to as crown sipes 25) include, for example, first crown sipes 26, second crown sipes 27, third crown sipes 28, and fourth crown sipes 29.

[0043] FIG. 5 shows an enlarged view of the first crown sipes 26, the second crown sipes 27, the third crown sipes 28, and the fourth crown sipes 29 in FIG. 2. As shown in FIG. 5, the first crown sipes 26 and the second crown sipes 27 communicate with the first crown circumferential groove 7 (shown in FIG. 2) and have discontinuous ends within the tread surface of the crown land portion 15. The third crown sipes 28 and the fourth crown sipes 29 communicate with, for example, the second crown circumferential groove 8 (shown in FIG. 2) and have discontinuous ends within the tread surface of the crown land portion 15. Such crown sipes 25 can provide friction on snowy roads while maintaining the rigidity of the crown land portion 15. This results in a well-balanced improvement in steering stability and on-snow performance.

[0044] figure 6 5 shows a cross section of the crown sipe 25 taken along line AA in FIG. 6 As shown in Fig. 1, the crown sipe 25 has a chamfered portion 38 formed therein and opens at the tread surface 15s. The chamfered portion 38 includes an inclined surface 38s cut out between the tread surface and the sipe wall. In this embodiment, the inclined surface 38s is slightly curved so as to be convex outward in the tire radial direction. The inclined surface 38s may be flat, for example. Such a chamfered portion 38 helps to equalize the ground pressure acting on the tread surface of the land portion, improving steering stability and uneven wear resistance.

[0045] As shown in FIG. 5 , the chamfer width of the chamfered portion 38 of the first crown sipe 26 desirably decreases toward the interrupted end 26a. Similarly, the chamfer width of the chamfered portion 38 of the third crown sipe 28 desirably decreases toward the interrupted end 28a. Such first crown sipes 26 and third crown sipes 28 can ensure a sufficient ground contact area in the center of the crown land portion 15 and reliably maintain steering stability. While the first crown sipe 26 of this embodiment has the chamfered portion substantially eliminated at the interrupted end 26a, this is not limiting, and the chamfered portion 38 may remain at the interrupted end 26a. The same applies to the third crown sipe 28. The chamfer width is the opening width of the chamfered portion in a plan view of the tread. The opening width refers to the width in a direction perpendicular to the sipe longitudinal direction.

[0046] The second crown sipes 27 and the fourth crown sipes 29 preferably have chamfered portions formed over the entire opening portion. The chamfer width of the chamfered portion 38 of the second crown sipes 27 is preferably constant in the longitudinal direction of the second crown sipes 27. Similarly, the chamfer width of the chamfered portion 38 of the fourth crown sipes 29 is preferably constant in the longitudinal direction of the fourth crown sipes 29. Furthermore, the chamfer width of the chamfered portion 38 of the fourth crown sipes 29 is 80% to 120% of the chamfer width of the chamfered portion 38 of the second crown sipes 27, and in this embodiment, these are substantially the same. Such second crown sipes 27 and fourth crown sipes 29 are useful for suppressing uneven wear of the crown land portion 15.

[0047] As shown in Fig. 2, in a plan view of the tread, it is desirable that at least one of the protrusions 20 (in this embodiment, the first protrusion 21) overlaps at least a portion of a region 36 (dotted in Fig. 2) formed by extending the end of the first crown circumferential groove 7 side of the first crown sipe 26 parallel to the tire axial direction. As a more desirable aspect, in this embodiment, in a plan view of the tread, the first protrusion 21 overlaps the region 36 so as to straddle it. This allows the first protrusion 21 to increase the rigidity around the first crown sipe 26, improving steering stability.

[0048] From a similar perspective, in a plan view of the tread, it is desirable that at least one of the protrusions 20 (in this embodiment, the second protrusion 22) overlaps with at least a portion of the region 37 (indicated by dots in Figure 2) extending parallel to the tire axial direction from the end of the second crown sipe 27 on the first crown circumferential groove 7 side.

[0049] In this embodiment, the first protrusions 21 and the second protrusions 22 are misaligned in the tire circumferential direction, so that in a plan view of the tread, the region 36 overlaps with the first protrusions 21 but does not overlap with the second protrusions 22. Similarly, the region 37 overlaps with the second protrusions 22 but does not overlap with the first protrusions 21. This is expected to improve steering stability while maintaining wet performance.

[0050] 5, these crown sipes 25 are inclined in the same direction relative to the tire axial direction. The angle of the crown sipes 25 relative to the tire axial direction is, for example, 10 to 50 degrees, and preferably 20 to 40 degrees. In this specification, the angle and length of the sipes are measured at the center line of the sipe.

[0051] The length L4 of the first crown sipe 26 in the tire axial direction is shorter than the length L7 of the fourth crown sipe 29 and is also shorter than the length L5 of the second crown sipe 27. In addition, the end 26a of the first crown sipe 26 is closer to the first crown circumferential groove 7 side (see FIG. 5 In a more preferable embodiment, the end 26a of the first crown sipe 26 is located closer to the second crown circumferential groove 8 (see FIG. 1) than the end 29a of the fourth crown sipe 29. 5 The first crown sipes 26 are positioned on the right side in the figure. The length L4 of the first crown sipes 26 is 25% to 45% of the axial width W4 of the tread surface 15s of the crown land portion 15. Such first crown sipes 26 are useful for improving steering stability, snow performance, and wet performance in a well-balanced manner.

[0052] The length L5 of the second crown sipe 27 in the tire axial direction is, for example, 40% to 60% of the width W4 of the tread surface 15s of the crown land portion 15 in the tire axial direction.

[0053] The axial length L6 of the third crown sipes 28 is, for example, shorter than the length L7 of the fourth crown sipes 29 and shorter than the length L5 of the second crown sipes 27. Specifically, the length L6 of the third crown sipes 28 is 25% to 45% of the width W4 of the tread surface 15s of the crown land portion 15.

[0054] The fourth crown sipes 29 desirably cross the axial center of the tread surface 15s of the crown land portion 15. The discontinuous ends 29a of the fourth crown sipes 29 are located closer to the first crown circumferential groove 7 than the discontinuous ends 27a of the second crown sipes 27. The axial length L7 of the fourth crown sipes 29 is desirably longer than the axial length L5 of the second crown sipes 27. Specifically, the length L7 of the fourth crown sipes 29 is 65% to 85% of the width W4 of the tread surface 15s of the crown land portion 15. Such fourth crown sipes 29 can improve on-snow performance and wet performance while maintaining driving stability.

[0055] As shown in FIG. 2, the distance from the center position of the first surface 31 of the first protrusion 21 in the tire axial direction to the end 29a of the fourth crown sipe 29 (shown in FIG. 5) Tire Circumferential Direction The distance L9 is 15% to 30% of the pitch P1 of the multiple protrusions 20. This arrangement of the fourth crown sipes 29 allows the land portion around the first surface 31 to deform appropriately. This makes it difficult for snow to become clogged around the first surface 31, thereby continuously demonstrating excellent on-snow performance.

[0056] A plurality of middle lateral grooves 40 are provided in the first middle land portion 13. For example, the middle lateral grooves 40 completely cross the first middle land portion 13 in the tire axial direction.

[0057] In a plan view of the tread, it is desirable that at least one of the protrusions 20 (the first protrusion 21 in this embodiment) overlaps with an area obtained by extending the end 40a of the middle lateral groove 40 on the first crown circumferential groove 7 side parallel to the tire axial direction. As a result, when driving on snow, snow pillars formed at the connection between the first crown circumferential groove 7 and the middle lateral groove 40 are sheared by the protrusion 20, thereby generating a large reaction force and further improving on-snow performance.

[0058] It is desirable that the end 40a of the middle lateral groove 40 and the first surface 31 of the second protrusion 22 are located relatively close to each other. Specifically, the circumferential distance L10 from the groove center of the end 40a to the axial center of the first surface 31 is, for example, 30% or less, and preferably 15% or less, of the pitch P1 of the protrusions 20. This suppresses uneven wear near the middle lateral groove 40. On the other hand, from the viewpoint of ensuring the drainage of the middle lateral groove 40, it is desirable that the distance L10 be 30% or more of the groove width of the middle lateral groove 40 at the end 40a.

[0059] The middle lateral grooves 40 include a first groove portion 46, a second groove portion 47, and a longitudinal groove portion 48. The first groove portion 46 extends axially from the shoulder first circumferential groove 5. The second groove portion 47 extends axially from the crown first circumferential groove 7. The angle of the first groove portion 46 with respect to the axial direction of the tire and the angle of the second groove portion 47 with respect to the axial direction of the tire are each 10 to 50 degrees, preferably 20 to 40 degrees. The longitudinal groove portion 48 communicates with the first groove portion 46 and the second groove portion 47 and extends circumferentially with the tire. The angle of the longitudinal groove portion 48 with respect to the circumferential direction of the tire is, for example, 10 degrees or less, preferably 5 degrees or less. Such middle lateral grooves 40 are useful for improving traction performance and cornering performance on snow.

[0060] In this embodiment, the cross-sectional shapes of the first groove portion 46 and the second groove portion 47 are different. FIG. 7 shows a cross-sectional view of the first groove portion 46 taken along line BB in FIG. 2 . FIG. 8 shows a cross-sectional view of the second groove portion 47 taken along line CC in FIG. 2 . As shown in FIGS. 7 and 8 , the first groove portion 46 and the second groove portion 47 each preferably have a chamfered portion 50 formed therein and open. The chamfered portion 50 includes an inclined surface 50s formed by cutting out between the tread surface of the land portion and the groove wall. In this embodiment, the inclined surface 50s is slightly curved so as to be convex outward in the tire radial direction. The inclined surface 50s may be flat, for example. Such a chamfered portion 50 helps to equalize the ground pressure acting on the tread surface 13s and improve uneven wear resistance.

[0061] The depth d2 of the first groove portions 46 (the depth excluding the groove bottom sipes 55 described below) is 40% to 60% of the maximum depth of the first crown circumferential groove 7. The depth d3 of the second groove portions 47 is, for example, 60% to 80% of the maximum depth of the first crown circumferential groove 7. The middle lateral grooves 40 having such first groove portions 46 and second groove portions 47 are useful for improving steering stability and on-snow performance in a balanced manner.

[0062] The first groove portion 46 is connected to groove bottom sipes 55 that open at the groove bottom 46d and extend in the tire radial direction. Such groove bottom sipes 55 make it easier for the first groove portion 46 to open appropriately, which helps improve on-snow performance.

[0063] As shown in FIG. 2 , the middle lateral grooves 40 of this embodiment include first middle lateral grooves 41, whose first groove portions 46 and second groove portions 47 have the shapes described above, and second middle lateral grooves 42, whose first groove portions 46 and second groove portions 47 have different configurations from those of the first middle lateral grooves 41. The first groove portions 46 of the second middle lateral grooves 42 have the cross-sectional shape shown in FIG. 8 , and the second groove portions 47 of the second middle lateral grooves 42 have the cross-sectional shape shown in FIG. 7 . In this embodiment, the first middle lateral grooves 41 and the second middle lateral grooves 42 are alternately arranged in the tire circumferential direction. This arrangement of the middle lateral grooves 40 uniforms the rigidity of the first middle land portion 13, improving uneven wear resistance.

[0064] As shown in FIG. 2 , the first middle land portion 13 is provided with a plurality of first middle sipes 51, a plurality of second middle sipes 52, and a plurality of longitudinal sipes 53. The first middle sipes 51 extend axially from the first shoulder circumferential groove 5 and have an end 51a in the tread surface of the first middle land portion 13. The second middle sipes 52 extend axially from the first crown circumferential groove 7 and have an end 52a in the tread surface of the first middle land portion 13. The longitudinal sipes 53 extend from the end 51a of the first middle sipe 51, across the longitudinal groove portion 48 of the first middle lateral groove 41, to the end 52a of the second middle sipe 52. These various sipes can improve traction and cornering performance on snow while maintaining steering stability.

[0065] The first middle sipes 51 and the second middle sipes 52 have chamfered portions 58 formed thereon, which are open at the tread surface. The chamfer width of the chamfered portions 58 of the first middle sipes 51 and the second middle sipes 52 desirably decreases toward the longitudinal sipe 53. This ensures a sufficient contact area in the center of the first middle land portion 13, thereby maintaining steering stability.

[0066] In a plan view of the tread, it is desirable that at least one of the protrusions 20 (in this embodiment, the second protrusion 22) overlaps with at least a part of a region formed by extending the end of the second middle sipe 52 on the first crown circumferential groove 7 side parallel to the tire axial direction. Such an arrangement of the second middle sipes 52 helps to improve steering stability and uneven wear resistance.

[0067] Although a 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 embodiment and can be modified and implemented in various aspects.

[0068] [Note] The present disclosure includes the following aspects.

[0069] [Disclosure 1] A tire having a tread portion, the tread portion includes a first tread edge, a second tread edge, a crown land portion provided between the first tread edge and the second tread edge, and a first crown circumferential groove adjacent to the first tread edge side of the crown land portion and extending continuously in the tire circumferential direction, a plurality of protrusions protruding in the tire radial direction are formed at a groove bottom of the first crown circumferential groove, The crown land portion is not provided with a drainage groove having an opening width at the tread surface exceeding 2.0 mm and a depth of an area where the distance between two groove walls exceeds 2.0 mm exceeding 2.0 mm, The crown land portion is provided with sipes. tire. [Disclosure 2] the protrusion has a vertically elongated shape having a width in the tire axial direction and a length in the tire circumferential direction that is greater than the width, The tire according to Disclosure 1, wherein the protrusion includes a tapered portion in which the width decreases toward one side in the tire circumferential direction. [Disclosure 3] the protrusions include a plurality of first protrusions aligned in the tire circumferential direction and a plurality of second protrusions aligned in the tire circumferential direction on the first tread edge side of the plurality of first protrusions, In each of the plurality of first protrusions, the width of the tapered portion decreases toward a first side in the tire circumferential direction, The tire described in Disclosure 2, wherein each of the plurality of second protrusions has the width of the tapered portion decreasing toward a second side opposite the first side in the tire circumferential direction. [Disclosure 4] the crown land portion is provided with a plurality of first crown sipes that communicate with the first crown circumferential groove and have discontinuous ends within a tread surface of the crown land portion, The tire according to any one of Disclosures 1 to 3, wherein, in a plan view of the tread, at least one of the protrusions overlaps with a region where an end portion of the first crown circumferential groove side of the first crown sipe extends parallel to the tire axial direction. [Disclosure 5] The first crown sipe has a chamfered portion formed therein, The tire described in Disclosure 4, wherein the chamfer width of the chamfered portion of the first crown sipe becomes smaller toward the discontinuous end. [Disclosure 6] the crown land portion is provided with a plurality of second crown sipes that communicate with the first crown circumferential groove and have discontinuous ends within a tread surface of the crown land portion, The second crown sipe has a chamfered portion formed therein, The tire according to any one of Disclosures 1 to 5, wherein the chamfer width of the chamfered portion of the second crown sipe is constant in the longitudinal direction of the second crown sipe. [Disclosure 7] The tire according to any one of Disclosures 1 to 6, wherein the crown land portion is provided on the tire equator. [Disclosure 8] the tread portion includes a second crown circumferential groove that is adjacent to the second tread end side of the crown land portion and extends continuously in the tire circumferential direction, The tire according to any one of Present Disclosures 1 to 7, wherein the groove bottom of the second crown circumferential groove is flat and not provided with the protrusion. [Disclosure 9] The tread portion has a specified orientation for installation on a vehicle, The tire according to any one of Disclosures 1 to 8, wherein the first tread edge is located on an outer side of the vehicle when mounted on the vehicle. [Disclosure 10] the tread portion includes a first middle land portion adjacent to the crown land portion via the first crown circumferential groove, The first middle land portion is provided with a plurality of middle lateral grooves communicating with the first crown circumferential groove, A tire described in any one of disclosures 1 to 9, wherein, in a plan view of the tread, at least one of the protrusions overlaps with a region where the end of the middle lateral groove on the first crown circumferential groove side extends parallel to the tire axial direction. [Explanation of symbols]

[0070] 2 Tread section 15 Crown Land Division 7 First crown circumferential groove 20 Protrusion 25 sipes T1 First tread edge T2 Second tread edge

Claims

1. A tire having a tread portion, the tread portion includes a first tread edge, a second tread edge, a crown land portion provided between the first tread edge and the second tread edge, and a first crown circumferential groove adjacent to the first tread edge side of the crown land portion and extending continuously in the tire circumferential direction, a plurality of protrusions protruding in the tire radial direction are formed at a groove bottom of the first crown circumferential groove, The crown land portion is not provided with a drainage groove having an opening width at the tread surface exceeding 2.0 mm and a depth of a region where the distance between two groove walls exceeds 2.0 mm exceeding 2.0 mm, The crown land portion is provided with a sipe, the protrusion has a vertically elongated shape having a width in the tire axial direction and a length in the tire circumferential direction that is greater than the width, The protrusion includes a tapered portion in which the width decreases toward one side in the tire circumferential direction. tire.

2. The protrusions include a plurality of first protrusions arranged in the tire circumferential direction, and a plurality of second protrusions arranged in the tire circumferential direction closer to the first tread end than the plurality of first protrusions, In each of the plurality of first protrusions, the width of the tapered portion decreases toward a first side in the tire circumferential direction, The tire according to claim 1 , wherein in each of the plurality of second protrusions, the width of the tapered portion decreases toward a second side opposite the first side in the tire circumferential direction.

3. A tire having a tread portion, the tread portion includes a first tread edge, a second tread edge, a crown land portion provided between the first tread edge and the second tread edge, a first crown circumferential groove adjacent to the first tread edge side of the crown land portion and extending continuously in the tire circumferential direction, and a second crown circumferential groove adjacent to the second tread edge side of the crown land portion and extending continuously in the tire circumferential direction, a plurality of protrusions protruding in the tire radial direction are formed at a groove bottom of the first crown circumferential groove, a groove bottom portion of the second crown circumferential groove is flat and is not provided with the protrusion portion, The crown land portion is not provided with a drainage groove having an opening width at the tread surface exceeding 2.0 mm and a depth of a region where the distance between two groove walls exceeds 2.0 mm exceeding 2.0 mm, The crown land portion is provided with sipes. tire.

4. A tire having a tread portion, the tread portion includes a first tread edge, a second tread edge, a crown land portion provided between the first tread edge and the second tread edge, a first crown circumferential groove adjacent to the first tread edge side of the crown land portion and extending continuously in the tire circumferential direction, and a first middle land portion adjacent to the crown land portion via the first crown circumferential groove, a plurality of protrusions protruding in the tire radial direction are formed at a groove bottom of the first crown circumferential groove, The crown land portion is not provided with a drainage groove having an opening width at the tread surface exceeding 2.0 mm and a depth of a region where the distance between two groove walls exceeds 2.0 mm exceeding 2.0 mm, The crown land portion is provided with a sipe, a plurality of middle lateral grooves communicating with the first crown circumferential groove are provided in the first middle land portion; In a tread plan view, at least one of the protrusions overlaps with a region of the middle lateral groove that extends parallel to the tire axial direction from an end portion of the middle lateral groove on the first crown circumferential groove side. tire.

5. The crown land portion is provided with a plurality of first crown sipes that communicate with the first crown circumferential groove and have discontinuous ends within the tread surface of the crown land portion, 5. The tire according to claim 1, wherein, in a tread plan view, at least one of the protrusions overlaps with a region formed by extending an end portion of the first crown circumferential groove side of the first crown sipe in a direction parallel to the tire axial direction.

6. The first crown sipe has a chamfered portion formed therein, The tire according to claim 5 , wherein a chamfer width of the chamfered portion of the first crown sipe decreases toward the discontinuous end.

7. The crown land portion is provided with a plurality of second crown sipes that communicate with the first crown circumferential groove and have discontinuous ends within the tread surface of the crown land portion, The second crown sipe has a chamfered portion formed therein, The tire according to claim 1 , wherein a chamfer width of the chamfered portion of the second crown sipe is constant in the longitudinal direction of the second crown sipe.

8. A tire described in any one of claims 1 to 7, wherein the crown land portion is located on the tire equator.

9. 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.

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