tire

Abstract

To provide a tire that can exert excellent noise performance, while maintaining wet performance.SOLUTION: A tire has a tread part. The tread part includes at least one circumferential groove continuously extending in a tire circumferential direction. In a groove bottom part 7d of a circumferential groove 7, are formed a plurality of protrusion parts 20 protruding in a tire radial direction. Each of the plurality of protrusion parts 20 is formed in a vertical-long shape which has a width in a tire axial direction and a length in the tire circumferential direction larger than the width. The plurality of protrusion parts 20 each include taper parts 23 whose widths gradually become smaller toward one side in the tire circumferential direction.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] This disclosure relates to tires.

Background Art

[0002] In Patent Document 1 below, a tire has been proposed in which a plurality of protrusions are formed on the bottom of a main groove that extends continuously in the tire circumferential direction. This tire is expected to improve traction performance and braking performance on snow by forming a snow column in the main groove and causing the protrusions to bite into the snow column when driving on snow.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] With the recent quieting of vehicles, there is also a demand for improving the noise performance of tires. On the other hand, it is also necessary to fully consider the wet performance of tires.

[0005] This disclosure has been devised in view of the above actual situation, and the main problem is to provide a tire that can exhibit excellent noise performance while maintaining wet performance.

Means for Solving the Problems

[0006] The present disclosure relates to a tire having a tread portion, wherein the tread portion includes at least one circumferential groove extending continuously in the circumferential direction of the tire, and a plurality of projections projecting in the radial direction of the tire are formed at the bottom of the circumferential groove, each of the plurality of projections being elongated having a width in the axial direction of the tire and a length in the circumferential direction of the tire that is greater than the width, and each of the plurality of projections includes a tapered portion in which the width decreases toward one side in the circumferential direction of the tire. [Effects of the Invention]

[0007] By adopting the above configuration, the tire disclosed herein can exhibit excellent noise performance while maintaining wet performance. [Brief explanation of the drawing]

[0008] [Figure 1] This is an exploded view of the tread portion showing one embodiment of the present disclosure. [Figure 2] Figure 1 shows an enlarged view of the crown land area, the first middle land area, and the first crown circumferential groove. [Figure 3] This is an enlarged perspective view of the circumferential groove of the first crown. [Figure 4] This is a magnified cross-sectional view of the protruding part. [Figure 5] Figure 2 shows enlarged views of the first, second, third, and fourth crown sipes. [Figure 6] This is a cross-sectional view along line AA in Figure 5. [Figure 7] Figure 2 is a cross-sectional view along line BB. [Figure 8] Figure 2 is a cross-sectional view along the CC line. [Modes for carrying out the invention]

[0009] Hereinafter, one embodiment of the present disclosure will be described with reference to the drawings. Figure 1 is an exploded view of the tread portion 2 of a tire 1 showing one 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 a passenger car. However, the present disclosure is not limited to this embodiment and may also be applied to pneumatic tires for heavy loads or non-pneumatic tires in which pressurized air is not filled inside the tire.

[0010] As shown in Figure 1, the tread portion 2 of the present disclosure includes a first tread end T1, a second tread end T2, a plurality of circumferential grooves 3 extending continuously in the circumferential direction of the tire between the first tread end T1 and the second tread end T2, and a plurality of land portions 4 divided by these circumferential grooves 3. In a preferred embodiment, the tire 1 of this embodiment is configured as a so-called five-rib tire in which the tread portion 2 is composed of four circumferential grooves 3 and five land portions 4.

[0011] In this embodiment, the tread portion 2 has a specified orientation for mounting to a vehicle. This ensures that the first tread end T1 is positioned on the outside of the vehicle when mounted, and the second tread end T2 is positioned on the inside of the vehicle when mounted. The mounting orientation is indicated, for example, by letters or symbols on the sidewall portion (not shown). However, the tire 1 of this disclosure is not limited to this configuration, and may not have a specified mounting orientation.

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

[0013] "Normal condition" refers to the state in the case of pneumatic tires for which various standards are defined, where the tire is mounted on a normal rim, filled to the normal internal pressure, and under no load. For tires for which various standards are not defined, or for non-pneumatic tires, the normal condition refers to the standard operating condition according to the intended use of the tire, and is under no load. Unless otherwise specified in this specification, the dimensions of each part of the tire are values ​​measured under normal condition. Furthermore, unless otherwise specified in this specification, known methods may be appropriately applied to the measurement methods of the aforementioned dimensions and material composition.

[0014] A "standard rim" is the rim defined for each tire within the standards system that the tire is based on. For example, it is the "standard rim" for JATMA, the "Design Rim" for TRA, and the "Measuring Rim" for ETRTO.

[0015] "Regular internal pressure" refers to the air pressure specified for each tire by each standard within the tire 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] "Regular load" refers to the load specified for each tire within the standard system, including the standard on which the tire is based, in the case of pneumatic tires for which various standards are defined. For example, it is the "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO. For tires for which no various standards are defined, "regular load" refers to the maximum load that can be applied when using the tire, in accordance with the above standards.

[0017] The circumferential groove 3 includes, for example, the first crown circumferential groove 7. The first crown circumferential groove 7 is provided on the first tread end T1 side of the tire equator C. Further, the circumferential groove 3 of the present embodiment includes 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 end 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 end T1. The second shoulder circumferential groove 6 is provided between the second crown circumferential groove 8 and the first tread end T1.

[0018] The distance L1 in the tire axial direction 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 distance L2 in the tire axial direction 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 distance in the tire axial direction from the first tread end T1 to the second tread end T2 in the normal state.

[0019] In the present embodiment, the first crown circumferential groove 7, the second crown circumferential groove 8, and the second shoulder circumferential groove 6 extend linearly in parallel with the tire circumferential direction. On the other hand, the groove edge on the tire equator C side of the first shoulder circumferential groove 5 extends in a zigzag shape. However, each circumferential groove 3 is not limited to such a shape.

[0020] The groove width W1 of each circumferential groove 3 is preferably at least 3 mm or more. Also, 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 this embodiment includes, for example, 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 in this embodiment is provided on the tire equator C. As a result, the first crown circumferential groove 7 is adjacent to the first tread end 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 end T1 and is divided on the tire axial side outward of the first shoulder circumferential groove 5. The second shoulder land portion 12 includes the second tread end T2 and is separated from the tire axial side of the second shoulder circumferential groove 6.

[0022] Figure 2 shows an enlarged view of the crown land portion 15, the first middle land portion 13, and the first crown circumferential groove 7. Figure 3 shows an enlarged perspective view of the groove bottom 7d of the first crown circumferential groove 7. As shown in Figures 2 and 3, the groove bottom 7d of the first crown circumferential groove 7 has a plurality of protrusions 20 that project in the radial direction of the tire. In Figure 2, the contours of the protrusions 20 that can be observed in a plan view of the tread are conceptually shown with solid lines, but these are omitted in Figure 1. In a preferred embodiment, the protrusions 20 are provided only in the first crown circumferential groove 7, but this disclosure is not limited to this embodiment, and the protrusions 20 may be provided in other circumferential grooves 3.

[0023] The tire 1 of this disclosure can exert a large reaction force by engaging the projection 20 with the snow columns formed in the circumferential groove 3 when driving on snow, and can exhibit excellent traction and braking performance on snow.

[0024] As shown in Figure 3, each of the multiple protrusions 20 is elongated in shape, having a width in the tire axial direction and a length in the tire circumferential direction that is greater than the width. Furthermore, each of the multiple protrusions 20 includes a tapered portion 23 in which the width decreases toward one side in the tire circumferential direction. By adopting the above configuration, the tire 1 of this disclosure can exhibit excellent noise performance while maintaining wet performance. The following mechanism is presumed to be the reason for this.

[0025] In the tire disclosed herein, since projections 20 are formed at the bottom of the circumferential grooves (in this embodiment, the first crown circumferential grooves 7), when driving on a dry road surface, the air passing through the circumferential grooves is easily disturbed by colliding with the projections 20. Furthermore, the speed of the disturbed air changes significantly when it passes near the tapered portion 23. Specifically, when the width of the tapered portion 23 is larger in the direction of air travel, the speed of the air decreases, and when the width of the tapered portion 23 is smaller in the direction of air travel, the speed of the air increases. This effect further promotes air disturbance within the circumferential grooves, thereby suppressing the generation of standing waves within the circumferential grooves and reducing air column resonance noise.

[0026] Furthermore, the tapered portion 23 can suppress the reduction in groove volume of the circumferential groove caused by the projection portion 20, thereby maintaining wet performance. Through this mechanism, the tire 1 of this disclosure can improve noise performance while maintaining wet performance.

[0027] 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 this disclosure can achieve the above-described effects even without the configurations described below. Furthermore, even if any one of the configurations described below is applied individually to a tire of this disclosure having the above-described features, an improvement in performance corresponding to each configuration can be expected. Moreover, if several of the configurations described below are applied in combination, a combined improvement in performance corresponding to each configuration can be expected.

[0028] As shown in Figure 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 projection 20 includes a first projection 21 arranged on the first groove wall 7a side and a second projection 22 arranged on the second groove wall 7b side. The first projection 21 and the second projection 22 have the same configuration except that their orientations are different. The multiple first projections 21 are arranged at a constant pitch in the circumferential direction of the tire. Similarly, the multiple second projections 22 are arranged at a constant pitch in the circumferential direction of the tire.

[0029] The maximum width W3 of one projection 20 in the tire axial direction is, for example, 30% to 70% of the maximum groove width W2 of the first crown circumferential groove 7. In this embodiment, when the first projection 21 and the second projection 22 are configured within the first crown circumferential groove 7, the width W3 of one projection 20 is 30% to 50% of the groove width W2, preferably 40% to 50%.

[0030] The length L3 of one projection 20 is, for example, 40% to 60% of the pitch P1 of the projection 20 in the tire circumferential direction. Also, the length L3 of one projection 20 in the tire circumferential direction is, for example, 2.0 to 4.0 times the width W3 of the projection 20. Such projections 20 have sufficient rigidity in the tire circumferential direction and can provide a large reaction force when shearing snow columns in the first crown circumferential groove 7 when driving on snow. However, the projections 20 are not limited to this configuration.

[0031] Figure 4 shows an enlarged cross-sectional view of the projection 20 along the longitudinal direction of the first crown circumferential groove 7. As shown in Figure 4, the maximum height h1 of the projection 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 preferably 10% to 20% of the depth d1. Such a projection 20 can exert the above-mentioned effects while maintaining the drainage performance of the first crown circumferential groove 7.

[0032] The projection 20 includes a first surface 31 that extends radially toward the tire and faces one side in the tire circumferential direction, and a second surface 32 positioned on the opposite side from 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, for example, connected to the first surface 31 via a ridge 35, and extends gently inclined from the ridge 35 toward the groove bottom 7d of the first crown circumferential groove 7. In this embodiment, the second surface 32 is, for example, slightly curved in a direction that is convex toward the outward radial direction of the tire, but it may also be configured as a flat surface. In this specification, "ridge" means a connecting portion formed by the connection of two surfaces with different extending directions, and having a longitudinal direction. In this specification, "ridge" also includes those that constitute a minute curved surface in its cross-section and have a substantial width.

[0033] The second surface 32 has a larger angle with respect to the tire radius than the first surface 31. The angle θ2 of the second surface 32 with respect to the tire radius at the outer end of the second surface 32 on the groove bottom 7d side is, for example, 70° or more, preferably 78-86°. The projection 20 including the first surface 31 and the second surface 32 can exert a large reaction force when the first surface 31 pushes back snow columns during driving on snow.

[0034] As shown in Figure 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 than the first side surface 33 with respect to the tire circumferential direction. The first side surface 33 and the second side surface 34 are connected to the second surface 32, for example, via a ridge, and extend from the ridge in the tire radial direction. Furthermore, the first side surface 33 and the second side surface 34 are connected to the first surface 31 via a ridge 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. As a result, the region of the first surface 31 on the groove centerline side is less likely to deform in the tire circumferential direction, and the above-mentioned effects can be further improved.

[0035] 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, help to improve not only snow performance but also wet performance and noise performance in a balanced manner. The angle θ3 is defined, for example, as the maximum angle between the ridge line formed between the first side surface 33 and the second surface 32 and the ridge line formed between the second side surface 34 and the second surface 32.

[0036] As shown in Figure 3, the first projection 21 and the second projection 22 are oriented in opposite directions in the tire circumferential direction. As a result, the width of each tapered portion 23 of the multiple first projections 21 decreases toward the first side R1 in the tire circumferential direction. Therefore, the first surface 31 of the first projection 21 faces the second side R2, which is opposite to the first side R1 in the tire circumferential direction. The second surface 32 of the first projection 21 is connected to the first side R1 of the first surface 31.

[0037] On the other hand, the width of each tapered portion 23 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 connected to the second side R2 of the first surface 31. With this arrangement of the first protrusions 21 and second protrusions 22, when driving on snow, if the protrusions 20 shear the snow columns compacted in the first crown circumferential groove 7 in the tire circumferential direction, the first protrusions 21 can provide a large reaction force on one side in the tire circumferential direction, and the second protrusions 22 can provide a large reaction force on the other side in the tire circumferential direction. Therefore, traction performance and braking performance on snow are improved in a well-balanced manner.

[0038] In a desirable embodiment, it is desirable that the first projection 21 and the second projection 22 are offset in the circumferential direction of the tire. Specifically, as shown in Figure 2, in a plan view of the tread, the overlapping length between the virtual region extending the first projection 21 parallel to the tire axis direction and the second projection 22 is 20% or less, more preferably 10% or less, of the circumferential length of the second projection 22, and in an even more desirable embodiment, it is desirable that the virtual region and the second projection 22 do not overlap. Such an arrangement of projections 20 can suppress snow from accumulating in the circumferential grooves 7 of the first crown when driving on snow, and helps to maintain excellent snow performance.

[0039] In this embodiment, the projection 20 is provided only in the first crown circumferential groove 7. That is, it is desirable that the bottom of the second crown circumferential groove 8 (shown in Figure 1) be flat and without the projection 20. Similarly, it is desirable that the bottom of the first shoulder circumferential groove 5 and the second shoulder circumferential groove 6 (shown in Figure 1) be flat and without the projection 20. This can improve wet performance. However, this disclosure is not limited to this embodiment, and from the viewpoint of further improving snow performance, the projection 20 may also be provided in the circumferential grooves 3 other than the first crown circumferential groove 7.

[0040] As shown in Figure 2, the crown land portion 15 does not have drainage grooves. A drainage groove is a groove that can provide substantial drainage, and means a groove in which the opening width on the tread surface exceeds 2.0 mm and the depth (length in the tire radial direction) of the region where the distance between two groove walls exceeds 2.0 mm exceeds 2.0 mm. On the other hand, the crown land portion 15 is provided with sipes 25.

[0041] In this specification, "sipe" means a groove-like body having a small width (a recess having a longitudinal direction, including grooves and sipes), wherein the width between the two inner walls in its main body is 1.5 mm or less. The main body also means the portion where the two inner walls extend substantially parallel to each other in the tire radial direction. In a preferred embodiment, the width of the main body of the sipe is, for example, 0.5 to 1.0 mm. As will be described later, the sipe may include a chamfered portion. The sipe may also have a so-called flask bottom with an increased width at the bottom.

[0042] In this embodiment, the crown land portion 15 has high rigidity because it does not have drainage grooves. Furthermore, because the crown land portion 15 is adjacent to the circumferential grooves provided with projections 20, the snow around the projections 20 can be compressed more strongly when driving on snow, and the projections 20 can provide a greater reaction force. On the other hand, the crown land portion 15 is provided with sipes 25, which improve snow performance.

[0043] The sipes 25 provided on the crown land section 15 (hereinafter sometimes referred to as crown sipes 25) include, for example, a first crown sipe 26, a second crown sipe 27, a third crown sipe 28, and a fourth crown sipe 29.

[0044] Figure 5 shows enlarged views of the first crown sipe 26, second crown sipe 27, third crown sipe 28, and fourth crown sipe 29 shown in Figure 2. As shown in Figure 5, the first crown sipe 26 and second crown sipe 27 communicate with the first crown circumferential groove 7 (shown in Figure 2) and have interrupted ends within the tread surface of the crown base 15. The third crown sipe 28 and fourth crown sipe 29 communicate with, for example, the second crown circumferential groove 8 (shown in Figure 2) and have interrupted ends within the tread surface of the crown base 15. Such crown sipes 25 can provide friction on snowy surfaces while maintaining the rigidity of the crown base 15. Therefore, handling stability and snow performance are improved in a balanced manner.

[0045] Figure 5 shows a cross-sectional view of the crown sipe 25, specifically the cross-sectional view along line AA in Figure 5. As shown in Figure 5, the crown sipe 25 has a chamfered portion 38 formed on it, opening 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 in a direction that is convex outward in the radial direction of the tire. The inclined surface 38s may also be, for example, flat. Such a chamfered portion 38 helps to equalize the ground pressure acting on the tread surface on land, improving handling stability and resistance to uneven wear.

[0046] As shown in Figure 5, it is desirable that the chamfer width of the chamfered portion 38 of the first crown sipe 26 decreases toward the interrupted end 26a. Similarly, it is desirable that the chamfer width of the chamfered portion 38 of the third crown sipe 28 decreases toward the interrupted end 28a. Such first and third crown sipes 26 and 28 can secure sufficient contact area in the central part of the crown land area 15 and reliably maintain steering stability. In this embodiment, the chamfered portion of the first crown sipe 26 is substantially gone at the interrupted end 26a, but the embodiment is not limited to this, 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 the direction perpendicular to the longitudinal direction of the sipe.

[0047] It is desirable that the second crown sipe 27 and the fourth crown sipe 29 have chamfered edges formed over the entire opening. It is desirable that the chamfer width of the chamfered edge 38 of the second crown sipe 27 be constant in the longitudinal direction of the second crown sipe 27. Similarly, it is desirable that the chamfer width of the chamfered edge 38 of the fourth crown sipe 29 be constant in the longitudinal direction of the fourth crown sipe 29. Furthermore, the chamfer width of the chamfered edge 38 of the fourth crown sipe 29 is 80% to 120% of the chamfer width of the chamfered edge 38 of the second crown sipe 27, and in this embodiment, these are substantially the same. Such second crown sipes 27 and fourth crown sipes 29 help to suppress uneven wear of the crown surface 15.

[0048] As shown in Figure 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 with at least a portion of the region 36 (in Figure 2, dots are shown) that extends parallel to the tire axis direction from the end of the first crown sipe 26 on the first crown circumferential groove 7 side. In a more desirable embodiment, in a plan view of the tread, the first protrusion 21 overlaps so as to straddle the region 36. This allows the first protrusion 21 to increase the rigidity around the first crown sipe 26, thereby improving handling stability.

[0049] From a similar viewpoint, in a plan view of the tread, it is desirable that at least one of the protrusions 20 (which is the second protrusion 22 in this embodiment) overlaps with at least a portion of the region 37 (indicated by dots in Figure 2) that is extended parallel to the tire axis direction from the end of the second crown sipe 27 on the first crown circumferential groove 7 side.

[0050] In this embodiment, the first projection 21 and the second projection 22 are offset in the circumferential direction of the tire. As a plan view of the tread, region 36 overlaps with the first projection 21 but does not overlap with the second projection 22. Similarly, region 37 overlaps with the second projection 22 but does not overlap with the first projection 21. This allows for improved handling stability while maintaining wet performance.

[0051] As shown in Figure 5, these crown sipes 25 are inclined in the same direction with respect to the tire axis. The angle of the crown sipes 25 with respect to the tire axis is, for example, 10 to 50°, preferably 20 to 40°. In this specification, the angle and length of the sipes are measured at the center line of the sipe.

[0052] The axial length L4 of the first crown sipe 26 is smaller than the length L7 of the fourth crown sipe 29 and smaller than the length L5 of the second crown sipe 27. Furthermore, the cut end 26a of the first crown sipe 26 is located on the side of the first crown circumferential groove 7 (left side in Figure 6) than the cut end 28a of the third crown sipe 28. In a more desirable embodiment, the cut end 26a of the first crown sipe 26 is located on the side of the second crown circumferential groove 8 (right side in Figure 6) than the cut end 29a of the fourth crown sipe 29. The length L4 of the first crown sipe 26 is 25% to 45% of the axial width W4 of the tread surface 15s of the crown land portion 15. Such a first crown sipe 26 helps to balance handling stability with snow performance and wet performance.

[0053] The axial length L5 of the second crown sipe 27 is, for example, 40% to 60% of the axial width W4 of the tread surface 15s of the crown land portion 15.

[0054] The axial length L6 of the third crown sipe 28 is, for example, smaller than the length L7 of the fourth crown sipe 29 and smaller than the length L5 of the second crown sipe 27. Specifically, the length L6 of the third crown sipe 28 is 25% to 45% of the width W4 of the tread surface 15s of the crown land portion 15.

[0055] The fourth crown sipe 29 is preferably positioned across the axial center of the tread surface 15s of the crown land area 15. The interrupted end 29a of the fourth crown sipe 29 is located closer to the first crown circumferential groove 7 than the interrupted end 27a of the second crown sipe 27. The axial length L7 of the fourth crown sipe 29 is preferably greater than the axial length L5 of the second crown sipe 27. Specifically, the length L7 of the fourth crown sipe 29 is 65% to 85% of the width W4 of the tread surface 15s of the crown land area 15. Such a fourth crown sipe 29 can improve snow performance and wet performance while maintaining handling stability.

[0056] As shown in Figure 2, the radial distance L9 from the center position in the tire axial direction of the first surface 31 of the first projection 21 to the interrupted end 29a of the fourth crown sipe 29 (shown in Figure 5) is 15% to 30% of the pitch P1 of the multiple projections 20. This arrangement of the fourth crown sipe 29 makes the land area around the first surface 31 more easily deformable. As a result, snow is less likely to accumulate around the first surface 31, and excellent snow performance is maintained over time.

[0057] Multiple middle lateral grooves 40 are provided in the first middle land section 13. The middle lateral grooves 40, for example, completely traverse the first middle land section 13 in the direction of the tire axis.

[0058] 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 with the region obtained by extending the end 40a of the middle lateral groove 40 on the first crown circumferential groove 7 side parallel to the tire axis direction. Due to this positional relationship between the protrusions 20 and the middle lateral groove 40, air whose flow is obstructed by the protrusions 20 is more likely to flow towards the middle lateral groove 40. This effect helps to reduce the air column resonance noise of the first crown circumferential groove 7 and improve noise performance.

[0059] It is desirable that the end portion 40a of the middle lateral groove 40 and the first surface 31 of the second projection 22 be located relatively close to each other. Specifically, the tire circumferential distance L10 from the groove center of the end portion 40a to the center of the tire axial direction of the first surface 31 is, for example, 30% or less of the pitch P1 of the projection 20, and preferably 15% or less. This suppresses uneven wear near the middle lateral groove 40. On the other hand, from the viewpoint of ensuring drainage of the middle lateral groove 40, it is desirable that the distance L10 is 30% or more of the groove width at the end portion 40a of the middle lateral groove 40.

[0060] The middle lateral groove 40 includes a first groove 46, a second groove 47, and a longitudinal groove 48. The first groove 46 extends from the first shoulder circumferential groove 5 in the tire axial direction. The second groove 47 extends from the first crown circumferential groove 7 in the tire axial direction. The angles of the first groove 46 and the second groove 47 with respect to the tire axial direction are 10 to 50°, preferably 20 to 40°, respectively. The longitudinal groove 48 communicates with the first groove 46 and the second groove 47 and extends in the tire circumferential direction. The angle of the longitudinal groove 48 with respect to the tire circumferential direction is, for example, 10° or less, preferably 5° or less. Such a middle lateral groove 40 helps to improve traction and cornering performance on snow.

[0061] In this embodiment, the cross-sectional shape of the first groove 46 and the cross-sectional shape of the second groove 47 are different. Figure 7 shows the cross-sectional view of the first groove 46, which is the cross-sectional view along line BB in Figure 2. Figure 8 shows the cross-sectional view of the second groove 47, which is the cross-sectional view along line CC in Figure 2. As shown in Figures 7 and 8, it is desirable that the first groove 46 and the second groove 47 each have a chamfered portion 50 formed and open. The chamfered portion 50 includes an inclined surface 50s cut out between the tread surface and the groove wall. In this embodiment, the inclined surface 50s is slightly curved in a direction that is convex outward in the radial direction of the tire. The inclined surface 50s may also be, for example, flat. Such a chamfered portion 50 helps to equalize the contact pressure acting on the tread surface 13s and improve resistance to uneven wear.

[0062] The depth d2 of the first groove 46 (the depth excluding the groove bottom sipe 55, which will be described later) is 40% to 60% of the maximum depth of the first crown circumferential groove 7. The depth d3 of the second groove 47 is, for example, 60% to 80% of the maximum depth of the first crown circumferential groove 7. A middle lateral groove 40 having such a first groove 46 and second groove 47 helps to improve handling stability and snow performance in a balanced way.

[0063] The first groove 46 has a series of groove bottom sipes 55 that open at the groove bottom 46d and extend in the radial direction of the tire. These groove bottom sipes 55 help to open the first groove 46 appropriately, thereby improving snow performance.

[0064] As shown in Figure 2, the middle lateral groove 40 of this embodiment includes a first middle lateral groove 41 in which the first groove portion 46 and the second groove portion 47 have the shapes described above, and a second middle lateral groove 42 in which the configuration of the first groove portion 46 and the second groove portion 47 differs from that of the first middle lateral groove 41. The first groove portion 46 of the second middle lateral groove 42 is configured with the cross-sectional shape shown in Figure 8, and the second groove portion 47 of the second middle lateral groove 42 is configured with the cross-sectional shape shown in Figure 7. In addition, in this embodiment, the first middle lateral groove 41 and the second middle lateral groove 42 are alternately provided in the circumferential direction of the tire. This arrangement of the middle lateral groove 40 makes the rigidity of the first middle land portion 13 uniform, improving resistance to uneven wear.

[0065] The first middle section 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 in the axial direction of the tire from the first shoulder circumferential groove 5 and have a terminated end 51a within the tread surface of the first middle section 13. The second middle sipes 52 extend in the axial direction of the tire from the first crown circumferential groove 7 and have a terminated end 52a within the tread surface of the first middle section 13. The longitudinal sipes 53 extend from the terminated end 51a of the first middle sipe 51, across the longitudinal groove section 48 of the first middle lateral groove 41, to the terminated end 52a of the second middle sipe 52. These various sipes can improve traction and cornering performance on snow while maintaining handling stability.

[0066] The first middle sipe 51 and the second middle sipe 52 have chamfered portions 58 formed on them and open at the tread surface. It is desirable that the chamfer width of the chamfered portions 58 of the first middle sipe 51 and the second middle sipe 52 decreases toward the longitudinal sipe 53 side. This ensures a contact area in the central part of the first middle ground portion 13 and maintains steering stability.

[0067] In a plan view of the tread, it is desirable that at least one of the projections 20 (in this embodiment, the second projection 22) overlaps with at least a portion of the region obtained by extending the end of the second middle sipe 52 on the first crown circumferential groove 7 side parallel to the tire axis direction. Such arrangement of the second middle sipe 52 helps to improve handling stability and resistance to uneven wear.

[0068] 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 specific embodiment described above and can be implemented in various modified forms.

[0069] [Note] This disclosure includes the following aspects.

[0070] [Disclosure 1] A tire having a tread portion, The tread portion includes at least one circumferential groove that extends continuously in the circumferential direction of the tire. Multiple protrusions projecting in the radial direction of the tire are formed at the bottom of the circumferential groove. Each of the aforementioned multiple protrusions is elongated vertically, having a width in the tire axial direction and a length in the tire circumferential direction that is greater than the aforementioned width. Each of the aforementioned multiple protrusions includes a tapered portion whose width decreases toward one side in the circumferential direction of the tire. tire. [Disclosure 2] The circumferential groove includes a first groove wall and a second groove wall, The projection includes a plurality of first projections arranged on the first groove wall side and a plurality of second projections arranged on the second groove wall side. The width of the tapered portion of each of the plurality of first protrusions decreases toward the first side in the circumferential direction of the tire. The tire according to Disclosure 1, wherein the width of the tapered portion of each of the plurality of second protrusions decreases toward the second side opposite to the first side in the tire circumferential direction. [Disclosure 3] In a plan view of the tread, the tapered portion is formed between a first side surface extending along the tire circumferential direction and a second side surface inclined at a larger angle than the first side surface with respect to the tire circumferential direction, as described in Disclosure 2. [Disclosure 4] The tire according to disclosure 3, wherein the first side surface is provided on the groove centerline side of the circumferential groove than the second side surface. [Disclosure 5] The aforementioned multiple protrusions are arranged at a constant pitch in the circumferential direction of the tire. The tire according to any one of disclosures 1 to 4, wherein the length of each of the plurality of protrusions is 45% to 50% of the pitch. [Disclosure 6] The tire according to any one of disclosures 1 to 5, wherein the maximum height of each of the projections in the radial direction of the tire is 20% or less of the maximum depth of the circumferential groove. [Disclosure 7] In a plan view of the tread, the tapered portion is formed between a first side surface extending along the tire circumferential direction and a second side surface inclined at a larger angle than the first side surface with respect to the tire circumferential direction. The tire according to any one of claims 1 to 6 of this disclosure, wherein the angle between the first side and the second side is 30° or less. [Explanation of symbols]

[0071] 2 Tread section 3 Circumferential groove 20 Protrusion 23 Tapered section

Claims

1. A tire having a tread portion, The tread portion includes at least one circumferential groove that extends continuously in the circumferential direction of the tire. Multiple protrusions projecting in the radial direction of the tire are formed at the bottom of the circumferential groove. Each of the aforementioned multiple protrusions is elongated vertically, having a width in the tire axial direction and a length in the tire circumferential direction that is greater than the aforementioned width. Each of the aforementioned multiple protrusions includes a tapered portion whose width decreases toward one side in the circumferential direction of the tire. The circumferential groove includes a first groove wall and a second groove wall, In a plan view of the tread, the tapered portion is formed between a first side surface extending along the circumferential direction of the tire and a second side surface inclined at a larger angle than the first side surface with respect to the circumferential direction of the tire. tire.

2. The projection is A first surface that faces one side in the circumferential direction of the tire and extends in the radial direction of the tire, The tire according to claim 1, comprising a second surface that is connected to the first surface and extends inclined toward the bottom of the circumferential groove.

3. The tire according to claim 1 or 2, wherein the first side surface is provided on the groove centerline side of the circumferential groove than the second side surface.

4. The projection includes a plurality of first projections arranged on the first groove wall side and a plurality of second projections arranged on the second groove wall side, The width of the tapered portion of each of the plurality of first protrusions decreases toward the first side in the circumferential direction of the tire. The tire according to any one of claims 1 to 3, wherein the width of the tapered portion of each of the plurality of second protrusions decreases toward the second side opposite to the first side in the circumferential direction of the tire.

5. The aforementioned multiple protrusions are arranged at a constant pitch in the circumferential direction of the tire. The tire according to any one of claims 1 to 4, wherein the length of each of the plurality of protrusions is 40% to 60% of the pitch.

6. The tire according to any one of claims 1 to 5, wherein the maximum height of each of the projections in the radial direction of the tire is 20% or less of the maximum depth of the circumferential groove.

7. In a plan view of the tread, the tapered portion is formed between a first side surface extending along the tire circumferential direction and a second side surface inclined at a larger angle than the first side surface with respect to the tire circumferential direction. The tire according to any one of claims 1 to 6, wherein the angle between the first side surface and the second side surface is 30° or less.

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