Tire

Abstract

To provide a tire which improves wet performance while keeping stability on a dry road surface.SOLUTION: A tire includes a tread part 2. The tread part 2 includes a first shoulder circumferential groove 5 and a first shoulder land part 11. The shoulder land part 11 includes a plurality of first shoulder lateral grooves 20. At least one of the first shoulder lateral grooves 20 includes: an inner end 20i which is communicated with the first shoulder circumferential groove 5; a maximum groove width part 21; and an outside part 22. The maximum groove width part 21 is positioned approximately at the center of a ground plane of the first shoulder land part 11 in a tire axial direction. A groove width of the inner end 20i and a groove width of the first shoulder lateral groove 20 at a first tread end T1 are each smaller than the maximum groove width. In the outside part 22, a groove width becomes smaller toward outside in the tire axial direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a tire.

Background Art

[0002] Patent Document 1 below proposes a pneumatic tire provided with a plurality of outer shoulder transverse grooves crossing an outer shoulder land portion. The pneumatic tire expects improvement in drainage performance and snow performance by the outer shoulder transverse grooves.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, there has been a demand for further improvement in wet performance of tires. On the other hand, the handling stability on a dry road surface should not be impaired by improving the wet performance.

[0005] The present disclosure has been devised in view of the above actual situation, and the main problem is to provide a tire that improves wet performance while maintaining handling stability on a dry road surface.

Means for Solving the Problems

[0006] The present disclosure relates to a tire having a tread portion, the tread portion including a plurality of circumferential grooves continuously extending in the tire circumferential direction between a first tread end and a second tread end, and a plurality of land portions divided by the plurality of circumferential grooves. The plurality of circumferential grooves include a first shoulder circumferential groove disposed closest to the first tread end side. The plurality of land portions include the first tread end and a first shoulder land portion divided by the first shoulder circumferential groove. A plurality of first shoulder transverse grooves extending from the first shoulder circumferential groove to a position beyond the first tread end are provided in the first shoulder land portion. At least one of the first shoulder transverse grooves includes an inner end communicating with the first shoulder circumferential groove, a maximum groove width portion forming a maximum groove width of the first shoulder transverse groove within the ground contact surface of the first shoulder land portion, and an outer portion on the outer side in the tire axial direction relative to the first tread end. The groove width at the inner end and the groove width of the first shoulder transverse groove on the first tread end are each smaller than the maximum groove width, and the outer portion has a groove width that decreases toward the outer side in the tire axial direction.

Advantages of the Invention

[0007] By adopting the above configuration, the tire of the present disclosure can improve wet performance while maintaining handling stability on a dry road surface.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a developed view of a tread portion 2 of a tire 1 showing an embodiment of the present disclosure. The tire 1 of the present embodiment is suitably used, for example, as a pneumatic tire for a passenger car. However, the present disclosure is not limited to such a mode, and may be applied to a pneumatic tire for heavy loads or a non-pneumatic tire in which the inside of the tire is not filled with pressurized air.

[0010] As shown in FIG. 1, the tread portion 2 of the present disclosure includes a plurality of circumferential grooves 3 that continuously extend in the tire circumferential direction between a first tread end T1 and a second tread end T2, and a plurality of land portions 4 divided by the plurality of circumferential grooves 3. The tire 1 of the present embodiment is configured as a so-called 5-rib tire in which the tread portion 2 is divided into five land portions 4 by four circumferential grooves 3. However, the present disclosure is not limited to such a mode.

[0011] In the present embodiment, the direction of mounting the tread portion 2 on the vehicle is specified, for example. As a result, the first tread end T1 is located on the outside of the vehicle when mounted on the vehicle. The second tread end T2 is located on the inside of the vehicle when mounted on the vehicle. The direction of mounting on the vehicle is indicated, for example, by letters or symbols on a sidewall portion (not shown). However, the tire 1 of the present disclosure is not limited to such a mode, and the direction of mounting on the vehicle may not be specified.

[0012] The first tread end T1 and the second tread end T2 respectively correspond to the outermost ground contact positions in the tire axial direction when 70% of the normal load is applied to the tire 1 in the normal state and the camber angle is 0° and it contacts the plane.

[0013] The "normal state" means that in the case of a pneumatic tire with various specifications defined, the tire is mounted on a normal rim and filled with the normal internal pressure, and moreover, it is in an unloaded state. In the case of a tire without various defined specifications or a non-pneumatic tire, the "normal state" means a standard usage state according to the purpose of use of the tire, and it means a state where the tire is not mounted on a vehicle and is unloaded. In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in the above-mentioned normal state.

[0014] The "normal rim" is the rim defined for each tire in a specification system including the specifications on which the tire is based. For example, in the case of JATMA, it is the "standard rim", in the case of TRA, it is the "Design Rim", and in the case of ETRTO, it is the "Measuring Rim".

[0015] The "normal internal pressure" is the air pressure defined for each tire in a specification system including the specifications on which the tire is based. In the case of JATMA, it is the "maximum air pressure", in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is the "INFLATION PRESSURE".

[0016] The "normal load" means that in the case of a pneumatic tire with various specifications defined, it is the load defined for each tire in a specification system including the specifications on which the tire is based. In the case of JATMA, it is the "maximum load capacity", in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is the "LOAD CAPACITY". Also, in the case of a tire without various defined specifications or a non-pneumatic tire, the "normal load" refers to the load acting on one tire in the standard mounting state of the tire. The above-mentioned "standard mounting state" means a state where the tire is mounted on a standard vehicle according to the purpose of use of the tire, and the vehicle is stationary on a flat road surface in a state where it can run.

[0017] The plurality of circumferential grooves 3 includes a first shoulder circumferential groove 5 disposed closest to the first tread end T1 side. Further, the plurality of circumferential grooves 3 of the present embodiment includes a second shoulder circumferential groove 6, a first crown circumferential groove 7, and a second crown circumferential groove 8. The second shoulder circumferential groove 6 is disposed closest to the second tread end T2 side. The first crown circumferential groove 7 is disposed between the first shoulder circumferential groove 5 and the tire equator C. The second crown circumferential groove 8 is disposed between the second shoulder circumferential groove 6 and the tire equator C.

[0018] The tire 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 tire axial distance L2 from the tire equator C to the groove center line of the first crown circumferential groove 7 or the second crown circumferential groove 8 is preferably, for example, 5% to 15% of the tread width TW. Note that the tread width TW is the tire axial distance from the first tread end T1 to the second tread end T2 in the normal state.

[0019] Each circumferential groove 3 of the present embodiment extends linearly, for example, parallel to the tire circumferential direction. Each circumferential groove 3 may extend in a wavy shape, for example.

[0020] The groove width W1 of each circumferential groove 3 is desirably at least 3 mm or more. Also, the groove width W1 of each circumferential groove 3 is preferably, for example, 4.0% to 8.5% of the tread width TW. Note that in this specification, the groove width is the distance between two edges of the groove in the normal state. Also, the two edges are the boundaries between the opening of the groove and the ground surface when 70% of the normal load is applied to the tire 1 in the normal state and the outer surface of the tread portion 2 is grounded flat with a camber angle of 0°.

[0021] In this embodiment, the first shoulder circumferential groove 5 has the smallest groove width among the plurality of circumferential grooves 3. However, the present disclosure is not limited to such a mode. In the case of a pneumatic tire for a passenger car, the depth of each circumferential groove 3 is preferably, for example, 5 to 10 mm.

[0022] The plurality of land portions 4 of the present disclosure include a first shoulder land portion 11. The first shoulder land portion 11 includes a first tread end T1 and is divided on the outer side in the tire axial direction of the first shoulder circumferential groove 5.

[0023] Furthermore, the land portion 4 of the present disclosure includes a second shoulder land portion 12, a first middle land portion 13, a second middle land portion 14, and a crown land portion 15. The second shoulder land portion 12 includes a second tread end T2 and is divided on the outer side in the tire axial direction of the second shoulder circumferential groove 6. 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 crown land portion 15 is divided between the first crown circumferential groove 7 and the second crown circumferential groove 8.

[0024] FIG. 2 shows an enlarged view of the first shoulder land portion 11. As shown in FIG. 2, a plurality of first shoulder transverse grooves 20 are provided in the first shoulder land portion 11. The first shoulder transverse grooves 20 extend from the first shoulder circumferential groove 5 to a position beyond the first tread end T1.

[0025] At least one of the first shoulder transverse grooves 20 includes an inner end 20i communicating with the first shoulder circumferential groove 5, a maximum groove width portion 21 forming the maximum groove width W2 of the first shoulder transverse groove 20 within the ground contact surface of the first shoulder land portion 11, and an outer portion 22 on the outer side in the tire axial direction than the first tread end T1. Note that the maximum groove width portion 21 includes not only the portion forming the maximum groove width W2 but also the portion constituting a groove width of 95% or more of the maximum groove width W2.

[0026] The groove width W3 at the inner end 20i of the first shoulder transverse groove 20 and the groove width W4 on the first tread end T1 of the first shoulder transverse groove 20 are each smaller than the maximum groove width W2. Also, the outer portion 22 of the first shoulder transverse groove 20 has a groove width that decreases toward the outer side in the tire axial direction. By adopting the above configuration, the present disclosure can improve wet performance while maintaining the handling stability on a dry road surface (hereinafter, may be simply referred to as "handling stability"). The reason is presumed to be the following mechanism.

[0027] In the present disclosure, the maximum groove width portion 21 of the first shoulder transverse groove 20 disposed within the ground contact surface of the first shoulder land portion 11 can exhibit excellent drainage performance, and the wet performance is significantly improved.

[0028] Also, in the present disclosure, since the groove width W3 at the inner end 20i of the first shoulder transverse groove 20 and the groove width W4 on the first tread end T1 are smaller than the maximum groove width W2, the first shoulder transverse groove 20 is less likely to open even when a ground contact pressure acts on the first shoulder land portion 11, and the pattern rigidity of the first shoulder land portion 11 is maintained. Therefore, the handling stability on a dry road surface is effectively maintained.

[0029] Furthermore, in the present disclosure, regarding the outer portion 22 of the first shoulder transverse groove 20, since the groove width decreases toward the outer side in the tire axial direction, the region outside the first tread end T1 of the first shoulder land portion 11 has high rigidity. Thus, for example, in the outer tire during turning, when the ground contact end moves outward in the tire axial direction as the ground contact pressure increases, the high-rigidity region comes into contact with the ground, and the handling stability is more reliably maintained. It is presumed that the tire of the present disclosure can improve wet performance while maintaining the handling stability on a dry road surface by the above mechanism.

[0030] Hereinafter, a more detailed configuration of the present embodiment will be described. Each configuration described below shows a specific aspect of the present embodiment. Therefore, it goes without saying that the present disclosure can exhibit the above-described effects even if it does not have the configurations described below. Further, even if any one of the configurations described below is applied alone to the tire of the present disclosure having the above-described features, an improvement in performance corresponding to each configuration can be expected. Furthermore, when some of the configurations described below are applied in combination, a combined improvement in performance corresponding to each configuration can be expected.

[0031] In the first shoulder land portion 11 of the present embodiment, only a plurality of first shoulder lateral grooves 20 are arranged, and no other grooves or recesses are arranged. Further, in the present embodiment, each of the plurality of first shoulder lateral grooves 20 is configured to have substantially the same shape. The pitch length P1 in the tire circumferential direction between two adjacent first shoulder lateral grooves 20 in the tire circumferential direction is, for example, 100% to 120% of the width W5 in the tire axial direction of the ground contact surface of the first shoulder land portion 11. However, the present disclosure is not limited to such an aspect. Note that the one pitch length is the distance in the tire circumferential direction between the groove center lines of two adjacent first shoulder lateral grooves 20 in the tire circumferential direction. Further, when the distance in the tire circumferential direction changes in the tire axial direction, the central value thereof is adopted.

[0032] The groove width W3 of the inner end 20i of the first shoulder lateral groove 20 is, for example, 50% to 90% of the maximum groove width W2, and preferably 70% to 80%. The first shoulder lateral groove 20 having such an inner end 20i helps to enhance the handling stability and wet performance in a well-balanced manner.

[0033] Figure 3 shows an enlarged view of the first shoulder transverse groove 20. As shown in Figure 3, the first shoulder transverse groove 20 of the present embodiment includes, for example, an inner portion 23 that extends outward in the tire axial direction from the inner end 20i with a constant groove width. The length L4 of the inner portion 23 in the tire axial direction is, for example, 10% to 30% of the width W5 of the ground contact surface of the first shoulder land portion 11 (shown in Figure 2 and the same hereinafter), preferably 15% to 25%. Such an inner portion 23 helps to improve the handling stability and wet performance in a well-balanced manner. Note that the configuration such as the length of the groove in this specification is defined as being measured along the groove center line.

[0034] The first shoulder transverse groove 20 includes, for example, a main body portion 25 between the inner portion 23 and the outer portion 22. The main body portion 25 includes the maximum groove width portion 21 described above. In the present embodiment, the maximum groove width portion 21 is continuous with the outer side of the inner portion 23 in the tire axial direction. Specifically, the edge 23a on one side in the tire circumferential direction of the inner portion 23 (the upper side in Figure 3) and the edge 21a on the one side in the tire circumferential direction of the maximum groove width portion 21 are directly and linearly continuous. Also, the edge 23b on the other side in the tire circumferential direction of the inner portion 23 (the lower side in Figure 3) and the edge 21b on the other side in the tire circumferential direction of the maximum groove width portion 21 are continuous via a longitudinal edge 24 that extends at an angle of 20 to 40° with respect to the tire circumferential direction. Thereby, the groove width of the first shoulder transverse groove 20 expands stepwise at the inner portion 23 and the maximum groove width portion 21.

[0035] As a result of various experiments, the developers found that the drainage performance of the first shoulder transverse groove 20 is significantly contributed by the drainage (groove volume) at approximately the center in the tire axial direction of the grounding surface of the first shoulder land portion 11. Therefore, as a desirable aspect, the maximum groove width portion 21 of the present embodiment is located approximately at the center in the tire axial direction of the grounding surface of the first shoulder land portion 11. Thereby, the maximum groove width portion 21 can exhibit higher drainage performance. Note that this configuration includes at least an aspect in which the maximum groove width portion 21 crosses the center position in the tire axial direction of the grounding surface of the first shoulder land portion 11. Further, the above configuration includes an aspect in which even when the maximum groove width portion 21 does not cross the center position, the distance between the maximum groove width portion 21 and the center position is 5% or less of the width W5 in the tire axial direction of the grounding surface of the first shoulder land portion 11.

[0036] As shown in FIG. 2, the maximum groove width W2 is, for example, 20% to 35% of the one pitch length P1 of the first shoulder transverse groove 20. The length L5 in the tire axial direction of the maximum groove width portion 21 is, for example, 25% to 45% of the width W5 in the tire axial direction of the grounding surface of the first shoulder land portion 11, and preferably 30% to 40%. The first shoulder transverse groove 20 having such a maximum groove width portion 21 can exhibit excellent wet performance while maintaining steering stability.

[0037] As shown in FIG. 3, the main body portion 25 includes, for example, a groove width reduction portion 26 in which the groove width becomes smaller from the maximum groove width portion 21 to the first tread end T1. One edge of the groove width reduction portion 26 in the tire circumferential direction is continuous with the edge 21a of the maximum groove width portion 21, and includes a portion 26a1 that extends at an angle larger than the edge of the maximum groove width portion 21 with respect to the tire axial direction, and a portion 26a2 that extends to the first tread end T1 at the same angle as the edge of the maximum groove width portion 21 with respect to the tire axial direction. Further, the other edge of the groove width reduction portion 26 in the tire circumferential direction includes a portion 26b1 that is directly and linearly continuous with the edge of the maximum groove width portion 21, and a portion 26b2 that extends to the first tread end T1 at an angle larger than the edge 21b of the maximum groove width portion 21 with respect to the tire axial direction. Such a groove width reduction portion 26 is less likely to generate a turbulent flow when water moves inside the groove, and can reduce the groove width near the first tread end T1 while maintaining the drainage performance of the first shoulder cross groove 20.

[0038] As shown in FIG. 2, the groove width W4 at the first tread end T1 of the first shoulder cross groove 20 is, for example, 45% to 70% of the maximum groove width W2, preferably 50% to 65%. Such a first shoulder cross groove 20 can reduce the pitch noise during dry road surface driving while exhibiting the above-described effects.

[0039] Preferably, in the outer portion 22 of the present embodiment, the groove width continuously decreases from the first tread end T1 toward the outer side in the tire axial direction. Thereby, uneven wear around the outer portion 22 is suppressed. However, the present disclosure is not limited to such a mode, and the outer portion 22 may include, for example, a portion that extends with a constant groove width.

[0040] The outer portion 22 includes, for example, a first portion 27 on the side of the first tread end T1 and a second portion 28 on the outer side of the first portion 27 in the tire axial direction. The groove width of the first portion 27 decreases toward the outer side in the tire axial direction at a first reduction rate. The groove width of the second portion 28 decreases toward the outer side in the tire axial direction at a second reduction rate that is smaller than the first reduction rate. Such an outer portion 22 can exhibit excellent handling stability even in a high-load state where a large load acts on the tread portion. The high-load state means a state in which a larger load acts on the tread portion than during normal running, such as the front wheels during braking or the outer wheels during turning, and the outer portion 22 (particularly the second portion 28) is in contact with the ground.

[0041] The first reduction rate and the second reduction rate are each defined as the ratio of the maximum groove width of each portion to the minimum groove width of that portion. The first reduction rate of the first portion 27 is, for example, 200% to 300%. The second reduction rate of the second portion 28 is, for example, 130% to 200%. Also, the angle between the two edges of the first portion 27 is, for example, 10 to 25°. The angle between the two edges of the second portion 28 is smaller than the above angle of the first portion 27 and is, for example, less than 10°.

[0042] The length L6 of the outer portion 22 in the tire axial direction is, for example, equal to or less than the width W5 of the ground contact surface of the first shoulder land portion 11 in the tire axial direction. Specifically, the length L6 is 70% to 90% of the width W5, preferably 75% to 85%. Also, as shown in FIG. 3, the length L7 of the first portion 27 in the tire axial direction is 20% to 50% of the length L6 of the outer portion 22 in the tire axial direction. The length L8 of the second portion 28 in the tire axial direction is 50% to 80% of the length L6 of the outer portion 22 in the tire axial direction (shown in FIG. 2 and the same hereinafter). Such an outer portion 22 can improve the handling stability and wet performance in the high-load state in a well-balanced manner.

[0043] From the perspective of sufficiently enhancing the handling stability in the high-load state, it is desirable that the length L8 of the second portion 28 is, for example, greater than the length L4 of the inner portion 23 in the tire axial direction. Also, from the perspective of ensuring sufficient lengths of the first portion 27 and the main body portion 25, it is desirable that the length L8 of the second portion 28 is, for example, smaller than the length L9 of the portion excluding the second portion 28 and the inner portion 23 in the tire axial direction from the first shoulder cross groove 20.

[0044] As shown in FIG. 2, the groove width W6 at the boundary between the first portion 27 and the second portion 28 is, for example, 25% to 35% of the maximum groove width W2. Also, the groove width W7 at the outer end in the tire axial direction of the first shoulder cross groove 20 is, for example, 10% to 30% of the maximum groove width W2, desirably 15% to 25%. The groove width at the outer end means the groove width at the tire axial ends of the two edges extending along the groove length direction.

[0045] The first shoulder cross groove 20 has, for example, the maximum depth in the main body portion 25. The maximum depth of the first shoulder cross groove 20 is, for example, 60% to 90% of the maximum depth of the first shoulder circumferential groove 5, desirably 70% to 80%.

[0046] The inner portion 23 has a smaller depth than the main body portion 25. The maximum depth of the inner portion 23 is, for example, 45% to 65% of the maximum depth of the first shoulder cross groove 20, desirably 50% to 60%.

[0047] The outer portion 22 becomes shallower, for example, toward the outer side in the tire axial direction. The depth at the outer end of the first shoulder cross groove 20 is, for example, 5% to 25% of the maximum depth of the first shoulder cross groove 20, desirably 10% to 20%. Such an outer portion 22 helps to improve the handling stability and wet performance in a well-balanced manner.

[0048] FIG. 4 shows a cross-sectional view taken along line A-A of the first shoulder transverse groove 20 in FIG. 2. As shown in FIG. 4, for the first shoulder transverse groove 20, it is desirable that, for example, a chamfered portion 30 is continuous with at least a part of the edge. The chamfered portion 30 includes an inclined surface 30a extending obliquely from the edge. The inclined surface 30a extends inclinedly between the grounding surface of the first shoulder land portion 11 and the groove wall of the first shoulder transverse groove 20. The angle of this inclined surface 30a with respect to the tire radial direction is, for example, 30 to 60°. The width of the inclined surface 30a in the tread plan view is, for example, 2 mm or less, preferably 0.5 to 1.5 mm. Also, the depth of the inclined surface 30a is, for example, 2 mm or less, preferably 0.5 to 1.5 mm. Such a chamfered portion 30 helps to suppress uneven wear of the first shoulder land portion 11. Note that even when a chamfered portion is continuous with the edge of the groove, the groove width of the groove in this specification is the distance between the two edges of the groove in the normal state. Also, as described above, the two edges are the boundaries between the opening of the groove and the grounding surface when 70% of the normal load is applied to the tire 1 in the normal state and the outer surface of the tread portion 2 is grounded flat with a camber angle of 0°.

[0049] In FIG. 3, dots are provided on the inclined surface 30a of the chamfered portion 30. As shown in FIG. 3, one edge in the tire circumferential direction (the upper edge in FIG. 3) and the other edge in the tire circumferential direction (the lower edge in FIG. 3) of the first shoulder transverse groove 20 of the present embodiment each include both a region where the chamfered portion 30 is continuous and a region where the chamfered portion 30 is not continuous (hereinafter, such a region is referred to as a non-chamfered portion 31). Note that the non-chamfered portion 31 refers to a location where the grounding surface of the first shoulder land portion 11 and the groove wall of the first shoulder transverse groove 20 are continuous and form a substantially right-angled corner portion.

[0050] The chamfered portion 30 continuous with the edge on one side preferably extends from the inner end 20i of the first shoulder transverse groove 20 to in front of the first tread end T1. That is, on the first tread end T1, the edge on one side is configured as an unchamfered portion 31. The distance between the end of the chamfered portion 30 and the first tread end T1 is, for example, 3 to 15 mm, preferably 5 to 10 mm. Further, the edge on one side extends linearly from the inner end 20i of the first shoulder transverse groove 20 to the maximum groove width portion 21. Further, the chamfered portion 30 continuous with the edge on one side extends with a constant width from the inner end 20i of the first shoulder transverse groove 20 to the maximum groove width portion 21. Thereby, uneven wear of the first shoulder land portion 11 is suppressed.

[0051] The chamfered portion 30 continuous with the edge on the other side is arranged at least in the inner portion 23 and the maximum groove width portion 21 of the first shoulder transverse groove 20. In the present embodiment, the chamfered portion 30 continuous with the edge on the other side extends from the maximum groove width portion 21 to a position beyond the first tread end T1. That is, on the first tread end T1, the chamfered portion 30 is continuous with the edge on the other side. The distance from the tire axial direction end of the chamfered portion 30 continuous with the edge on the other side to the first tread end T1 is, for example, 5 mm or less.

[0052] As described above, in the present embodiment, on the first tread end T1, the edge on one side of the first shoulder transverse groove 20 is configured as the unchamfered portion 31, and the chamfered portion 30 is continuous with the edge on the other side of the first shoulder transverse groove 20. Such an arrangement of the chamfered portion 30 can suppress uneven wear in the vicinity of the first tread end T1 of the first shoulder transverse groove 20 while ensuring the frictional force by the edge in the vicinity of the first tread end T1.

[0053] The inner part 23 and the maximum groove width part 21 of the first shoulder transverse groove 20 are configured such that chamfered parts 30 are continuous with the edges on both sides, excluding the longitudinal edge 24. Also, one edge 22a in the tire circumferential direction of the outer part 22 is entirely configured as a non-chamfered part 31. Further, for the other edge 22b in the tire circumferential direction of the outer part 22, the chamfered part 30 is continuous only at the end part on the first tread end T1 side, and the other parts are configured as non-chamfered parts 31. For this reason, at least the second part 28 has non-chamfered parts 31 forming the edges on both sides. Thereby, uneven wear of the first shoulder land part 11 is suppressed, and when the outer part 22 comes into contact with the ground, the non-chamfered part 31 can provide a large frictional force.

[0054] From the same perspective, for one edge 25a in the tire circumferential direction of the main body part 25, the chamfered part 30 is continuous at the part continuous with the maximum groove width part 21, and at the end part on the first tread end T1 side, it is configured as a non-chamfered part 31. The other edge 25b in the tire circumferential direction of the main body part 25 is configured such that the chamfered part 30 is continuous throughout.

[0055] Fig. 5 shows an enlarged view of the second shoulder land part 12. As shown in Fig. 5, a plurality of second shoulder transverse grooves 35 are provided in the second shoulder land part 12. The second shoulder transverse groove 35 of the present embodiment includes, for example, a main body part 36 extending from a position away from the second shoulder circumferential groove 6 to the second tread end T2, and an outer part 37 on the outer side in the tire axial direction from the second tread end T2. The configuration of the outer part 22 (shown in Figs. 2 and 3) of the first shoulder transverse groove 20 described above can be applied to the outer part 37 of the second shoulder transverse groove 35. Also, the configuration of the main body part 25 of the first shoulder transverse groove 20 can be applied to the main body part 36 of the second shoulder transverse groove 35, excluding the configuration described below.

[0056] The tire axial distance L10 from the main body portion 36 of the second shoulder transverse groove 35 to the second shoulder circumferential groove 6 is, for example, 5% to 15% of the tire axial width W8 of the contact surface of the second shoulder land portion 12. The second shoulder transverse groove 35 including such a main body portion 36 can enhance the wet performance while maintaining the rigidity of the second shoulder land portion 12.

[0057] The main body portion 36 of the second shoulder transverse groove 35 includes an inclined edge 35a that extends obliquely in the tire circumferential direction at the inner end in the tire axial direction. The angle of the inclined edge 35a with respect to the tire circumferential direction is, for example, 20 to 40°. Such an inclined edge 35a also provides frictional force in the tire axial direction and improves the turning performance on a wet road surface.

[0058] The second shoulder transverse groove 35 of the present embodiment includes a standard type second shoulder transverse groove 35A and a second shoulder transverse groove 35B with a shallow groove. Also, in the present embodiment, the standard type second shoulder transverse groove 35A and the second shoulder transverse groove 35B with a shallow groove are alternately provided in the tire circumferential direction.

[0059] There is no groove arranged between the main body portion 36 of the standard type second shoulder transverse groove 35A and the second shoulder circumferential groove 6. The second shoulder transverse groove 35B with a shallow groove includes a shallow groove portion 38 that extends from its main body portion 36 to the second shoulder circumferential groove 6. The groove width and depth of the shallow groove portion 38 are, for example, 0.3 to 1.5 mm, preferably 0.5 to 1.0 mm. Such a shallow groove portion 38 can supplement the frictional force in the tire axial direction on a wet road surface.

[0060] FIG. 6 shows an enlarged view of the first middle land portion 13, the second middle land portion 14, and the crown land portion 15. As shown in FIG. 6, a plurality of first middle transverse grooves 41 and a plurality of first middle interrupted grooves 42 are provided in the first middle land portion 13. It is desirable that the first middle transverse grooves 41 and the first middle interrupted grooves 42 are alternately provided in the tire circumferential direction.

[0061] The first middle transverse groove 41 includes, for example, a main body portion 43 extending in the tire axial direction from the first shoulder circumferential groove 5, and a shallow groove portion 44 extending from the main body portion 43 to the first crown circumferential groove 7.

[0062] The main body portion 43 preferably communicates with the first shoulder circumferential groove 5 at a position different from the inner portion 23 of the first shoulder transverse groove 20 in the tire circumferential direction. Thereby, the pitch sounds of the respective transverse grooves are suppressed from overlapping, and uneven wear of each land portion is suppressed.

[0063] The main body portion 43 of the first middle transverse groove 41 is arranged, for example, at an angle of 10° or less with respect to the tire axial direction. The length L11 of the main body portion 43 in the tire axial direction is, for example, 40% to 60% of the width W9 of the ground contact surface of the first middle land portion 13 in the tire axial direction. In a more preferable aspect, the length L11 of the main body portion 43 of the first middle transverse groove 41 in the tire axial direction is larger than the length of the inner portion 23 (shown in FIG. 2) of the first shoulder transverse groove 20 in the tire axial direction and smaller than the length of the main body portion 43 (shown in FIG. 2) of the first shoulder transverse groove 20 in the tire axial direction. The first middle transverse groove 41 having such a main body portion 43 helps to enhance the handling stability and wet performance in a well-balanced manner.

[0064] The maximum groove width of the main body portion 43 is preferably smaller than the maximum groove width W2 (shown in FIG. 2) of the first shoulder transverse groove 20 and preferably smaller than the groove width W3 (shown in FIG. 2) at the inner end 20i of the first shoulder transverse groove 20. The maximum groove width of the main body portion 43 is 35% to 50% of the maximum groove width W2 of the first shoulder transverse groove 20. The first middle transverse groove 41 including such a main body portion 43 can enhance the handling stability and wet performance in cooperation with the first shoulder transverse groove 20.

[0065] The main body portion 43 includes, for example, a wide portion 43a continuous with the first shoulder circumferential groove 5 and a narrow portion 43b having a groove width smaller than that of the wide portion 43a. The groove width of the narrow portion 43b is 60% to 90% of the groove width of the wide portion 43a.

[0066] FIG. 7 shows a cross-sectional view taken along line B-B of FIG. 6. As shown in FIG. 7, it is desirable that a chamfered portion 45 is continuous with the edge of the main body portion 43 of the first middle transverse groove 41. Further, a narrow groove portion 46 having a width of 0.5 to 1.5 mm is continuous with the inner side in the tire radial direction of the chamfered portion 45. The depth of the main body portion 43 including the chamfered portion 45 and the narrow groove portion 46 is, for example, 40% to 60% of the maximum depth of the first shoulder circumferential groove 5. The first middle transverse groove 41 having such a main body portion 43 can maintain the rigidity of the first middle land portion 13 and improve the handling stability.

[0067] As shown in FIG. 6, the groove width and depth of the shallow groove portion 44 of the first middle transverse groove 41 are, for example, 0.3 to 1.5 mm, preferably 0.5 to 1.0 mm. Further, the shallow groove portion 44 is arranged, for example, at an angle larger than that of the main body portion 43 with respect to the tire axial direction. The angle of the shallow groove portion 44 with respect to the tire axial direction is, for example, 50 to 70°. Such a shallow groove portion 44 can provide frictional force in the tire axial direction by its edge and improve the turning performance on a wet road surface.

[0068] The first middle interrupted groove 42 extends, for example, from the first shoulder circumferential groove 5 and is interrupted within the first middle land portion 13. The tire axial length L12 of the first middle interrupted groove 42 is, for example, smaller than the tire axial length of the main body portion 43 of the first middle transverse groove 41. Specifically, the length L12 of the first middle interrupted groove 42 is 20% to 30% of the tire axial width W9 of the contact surface of the first middle land portion 13. Such a first middle interrupted groove 42 can improve the wet performance while maintaining the rigidity of the first middle land portion 13.

[0069] The cross-section of the first middle interrupted groove 42 is substantially the same as the cross-section of the main body portion 43 of the first middle transverse groove 41 shown in FIG. 7. Therefore, the configuration of the cross-section of the first middle transverse groove 41 can be applied to the cross-section of the first middle interrupted groove 42.

[0070] As shown in FIG. 6, a plurality of second middle land grooves 50 are provided in the second middle land portion 14. The second middle land groove 50 includes a main body portion 51 extending from the second shoulder circumferential groove 6 and a shallow groove portion 52 extending from the main body portion 51 to the second crown circumferential groove 8. The configuration of the main body portion 43 and the shallow groove portion 44 of the first middle land groove 41 described above can be applied to the main body portion 51 and the shallow groove portion 52 of the second middle land groove 50, except for the matters described below.

[0071] The main body portion 51 of the second middle land groove 50 is interrupted, for example, without crossing the center position in the tire axial direction of the ground contact surface of the second middle land portion 14. The length L13 in the tire axial direction of the main body portion 51 of the second middle land groove 50 is 30% to 50% of the width W10 in the tire axial direction of the ground contact surface of the second middle land portion 14. In a more desirable embodiment, the length L13 in the tire axial direction of the main body portion 51 of the second middle land groove 50 is smaller than the length L11 in the tire axial direction of the main body portion 43 of the first middle land groove 41. The second middle land groove 50 having such a main body portion 51 can enhance the wet performance while moderately maintaining the rigidity of the second middle land portion 14.

[0072] A plurality of first crown land grooves 56 and a plurality of second crown land grooves 57 are provided in the crown land portion 15.

[0073] The first crown land groove 56 extends from the first crown circumferential groove 7 and is interrupted within the crown land portion 15 without reaching the second crown circumferential groove 8. The length L14 in the tire axial direction of the first crown land groove 56 is, for example, 10% to 30% of the width W11 in the tire axial direction of the ground contact surface of the crown land portion 15. In a desirable embodiment, the length L14 of the first crown land groove 56 is smaller than any of the length L11 in the tire axial direction of the main body portion 43 of the first middle land groove 41, the length L12 in the tire axial direction of the first middle interrupted groove 42, and the length L13 in the tire axial direction of the main body portion 51 of the second middle land groove 50. Such a first crown land groove 56 can surely maintain the rigidity of the crown land portion 15 while compensating for the wet performance and can enhance the handling stability.

[0074] The second crown transverse groove 57 includes, for example, a main body portion 58 that extends in the tire axial direction from the second crown circumferential groove 8, and a shallow groove portion 59 that extends from the main body portion 58 and terminates without reaching the first crown circumferential groove 7.

[0075] The main body portion 58 of the second crown transverse groove 57 extends from the second crown circumferential groove 8 and terminates within the crown land portion 15 without reaching the first crown circumferential groove 7. The axial length L15 of the main body portion 58 of the second crown transverse groove 57 is, for example, 45% to 60% of the axial width W11 of the contact surface of the crown land portion 15. In a preferred embodiment, the length L15 of the main body portion 58 of the second crown transverse groove 57 is preferably smaller than the axial length L11 of the main body portion 43 of the first middle transverse groove 41 and larger than the axial length L13 of the main body portion 51 of the second middle transverse groove 50. The second crown transverse groove 57 including such a main body portion 58 helps to enhance the handling stability and wet performance in a well-balanced manner.

[0076] The groove width and depth of the shallow groove portion 59 of the second crown transverse groove 57 are, for example, 0.3 to 1.5 mm, preferably 0.5 to 1.0 mm. The shallow groove portion 59 of the second crown transverse groove 57 extends, for example, at an angle larger than that of the main body portion 58 with respect to the tire axial direction. Also, the shallow groove portion 59 of the second crown transverse groove 57 is inclined in the same direction as the shallow groove portion 44 of the first middle transverse groove 41. The angle of the shallow groove portion 59 of the second crown transverse groove 57 with respect to the tire axial direction is, for example, 50 to 70°. The second crown transverse groove 57 including such a shallow groove portion 59 helps to enhance the turning performance during wet driving.

[0077] As described above, the tire according to an embodiment of the present disclosure has been described in detail. However, the present disclosure is not limited to the above specific embodiments and can be implemented with various modifications.

Example

[0078] A tire of size 225 / 50R17 having the basic pattern of FIG. 1 was prototyped based on the specifications in Tables 1 to 3. Also, as a comparative example, a tire having the tread portion shown in FIG. 8 was prototyped. The shoulder lateral grooves a of the tires in the comparative examples all extend in the tire axial direction with a constant groove width. The tires in the comparative examples are substantially the same as those shown in FIG. 1 except for the above matters. The handling stability and wet performance of each test tire were tested. The common specifications and test methods of each test tire are as follows. Mounting rim: 17×7.5J Tire internal pressure: 220 kPa for the front wheels and 240 kPa for the rear wheels Test vehicle: A vehicle with a displacement of 2000 cc and rear-wheel drive Tire mounting position: All wheels

[0079] <Handling stability> The handling stability when the above test vehicle was driven on a dry road surface was evaluated by the driver's sensory feeling. The result is a score with the handling stability of the comparative example being 100, and the larger the numerical value, the better the handling stability.

[0080] <Wet performance> The wet performance when the above test vehicle was driven on a wet road surface was evaluated by the driver's sensory feeling. The result is a score with the wet performance of the comparative example being 100, and the larger the numerical value, the better the wet performance. The test results are shown in Tables 1 to 3.

[0081]

Table 1

[0082]

Table 2

[0083]

Table 3

[0084] As shown in Tables 1 to 3, it can be understood that the tires of the examples have significantly improved handling stability and wet performance compared to the comparative examples. That is, it was confirmed that the tires of the present disclosure improve wet performance while maintaining handling stability on dry road surfaces.

[0085] [Appendix] The present disclosure includes the following aspects.

[0086] [Disclosure 1] A tire having a tread portion, The tread portion includes a plurality of circumferential grooves continuously extending in the tire circumferential direction between a first tread end and a second tread end, and a plurality of land portions divided by the plurality of circumferential grooves, The plurality of circumferential grooves include a first shoulder circumferential groove disposed on the side closest to the first tread end, The plurality of land portions include the first tread end and a first shoulder land portion divided by the first shoulder circumferential groove, A plurality of first shoulder transverse grooves extending from the first shoulder circumferential groove to a position beyond the first tread end are provided in the first shoulder land portion, At least one of the first shoulder transverse grooves includes an inner end communicating with the first shoulder circumferential groove, a maximum groove width portion forming the maximum groove width of the first shoulder transverse groove within the ground contact surface of the first shoulder land portion, and an outer portion on the outer side in the tire axial direction of the first tread end, The groove width at the inner end and the groove width of the first shoulder transverse groove on the first tread end are each smaller than the maximum groove width, The outer portion has a groove width that decreases toward the outer side in the tire axial direction. Tire. [Disclosure 2] The tire according to Disclosure 1, wherein the groove width at the inner end is 50% to 70% of the maximum groove width. [Disclosure 3] The first shoulder transverse groove includes an outer end in the tire axial direction, The tire according to Disclosure 1 or 2, wherein the groove width at the outer end is 10% to 30% of the maximum groove width. [Disclosure 4] The outer portion includes a first portion and a second portion axially outside the first portion in the tire axial direction. The groove width of the first portion decreases toward the outside in the tire axial direction at a first reduction rate. The tire according to any one of Disclosures 1 to 3, wherein the groove width of the second portion decreases toward the outside in the tire axial direction at a second reduction rate smaller than the first reduction rate. [Disclosure 5] The first shoulder cross groove further includes an inner portion extending axially outside from the inner end with a constant groove width. The tire according to Disclosure 4, wherein the axial length of the second portion in the tire axial direction is larger than the axial length of the inner portion in the tire axial direction. [Disclosure 6] The tire according to Disclosure 4 or 5, wherein the axial length of the second portion in the tire axial direction is smaller than the axial length of the portion excluding the second portion and the inner portion from the first shoulder cross groove in the tire axial direction. [Disclosure 7] The first shoulder cross groove includes an edge on one side in the tire circumferential direction and an edge on the other side in the tire circumferential direction. Chamfered portions are continuously provided on the one-side edge and the other-side edge, respectively. The tire according to any one of Disclosures 1 to 6, wherein the chamfered portion includes an inclined surface extending obliquely from the edge. [Disclosure 8] The tire according to Disclosure 7, wherein the chamfered portion continuous with the one-side edge extends from the inner end of the first shoulder cross groove to before the first tread end. [Disclosure 9] The one-side edge extends linearly from the inner end to the maximum groove width portion. The tire according to Disclosure 7 or 8, wherein the chamfered portion continuous with the one-side edge extends with a constant width from the inner end to the maximum groove width portion. [Disclosure 10] The first shoulder transverse groove further includes an inner portion that extends outward in the tire axial direction from the inner end with a constant groove width. The chamfered portion connected to the other edge is arranged at least in the inner portion and the maximum groove width portion. The tire according to any one of Disclosures 7 to 9 of the present disclosure. [Disclosure 11 of the present disclosure] The chamfered portion connected to the other edge extends from the maximum groove width portion to a position beyond the first tread end. The tire according to any one of Disclosures 7 to 10 of the present disclosure.

Explanation of reference numerals

[0087] 2 Tread portion 3 Circumferential grooves 4 Land portion 5 First shoulder circumferential groove 11 First shoulder land portion 20 First shoulder transverse groove 20i Inner end 21 Maximum groove width portion 22 Outer portion T1 First tread end T2 Second tread end

Claims

1. A tire having a tread portion, wherein the tread portion includes a plurality of circumferential grooves continuously extending in the tire circumferential direction between a first tread edge and a second tread edge, and a plurality of land portions partitioned by the plurality of circumferential grooves, the plurality of circumferential grooves including a first shoulder circumferential groove disposed closest to the first tread edge side, the plurality of land portions including the first tread edge and a first shoulder land portion partitioned by the first shoulder circumferential groove, only a plurality of first shoulder lateral grooves extending from the first shoulder circumferential groove to a position beyond the first tread edge are provided in the first shoulder land portion, each of the first shoulder lateral grooves includes an inner end communicating with the first shoulder circumferential groove, a maximum groove width portion forming a maximum groove width of the first shoulder lateral groove within the ground contact surface of the first shoulder land portion, and an outer portion on the outer side in the tire axial direction than the first tread edge, the groove width at the inner end and the groove width of the first shoulder lateral groove on the first tread edge are each smaller than the maximum groove width, the outer portion has a groove width that decreases toward the outer side in the tire axial direction, a tire.

2. A tire having a tread portion, wherein the tread portion includes a plurality of circumferential grooves continuously extending in the tire circumferential direction between a first tread edge and a second tread edge, and a plurality of land portions partitioned by the plurality of circumferential grooves, the plurality of circumferential grooves including a first shoulder circumferential groove disposed closest to the first tread edge side, the plurality of land portions including the first tread edge and a first shoulder land portion partitioned by the first shoulder circumferential groove, a plurality of first shoulder lateral grooves extending from the first shoulder circumferential groove to a position beyond the first tread edge are provided in the first shoulder land portion, at least one of the first shoulder lateral grooves includes an inner end communicating with the first shoulder circumferential groove, a maximum groove width portion forming a maximum groove width of the first shoulder lateral groove within the ground contact surface of the first shoulder land portion, and an outer portion on the outer side in the tire axial direction than the first tread edge, the groove width at the inner end and the groove width of the first shoulder lateral groove on the first tread edge are each smaller than the maximum groove width, the outer portion has a groove width that decreases toward the outer side in the tire axial direction, the outer portion includes a first portion and a second portion on the outer side in the tire axial direction of the first portion. The groove width of the first part decreases toward the outside in the tire axial direction at a first reduction rate, the groove width of the second part decreases toward the outside in the tire axial direction at a second reduction rate smaller than the first reduction rate, a tire.

3. The first shoulder lateral groove further includes an inner part extending outward in the tire axial direction with a constant groove width from the inner end, The length of the second part in the tire axial direction is greater than the length of the inner part in the tire axial direction. The tire according to claim 2.

4. The first shoulder lateral groove further includes an inner part extending outward in the tire axial direction with a constant groove width from the inner end, The length of the second part in the tire axial direction is smaller than the length of the part excluding the second part and the inner part from the first shoulder lateral groove in the tire axial direction. The tire according to claim 2 or 3.

5. A tire having a tread part, The tread part includes a plurality of circumferential grooves continuously extending in the tire circumferential direction between a first tread end and a second tread end, and a plurality of land parts divided by the plurality of circumferential grooves, The plurality of circumferential grooves includes a first shoulder circumferential groove arranged closest to the first tread end side, The plurality of land parts includes the first tread end and a first shoulder land part divided by the first shoulder circumferential groove, A plurality of first shoulder lateral grooves extending from the first shoulder circumferential groove to a position beyond the first tread end are provided in the first shoulder land part, At least one of the first shoulder lateral grooves includes an inner end communicating with the first shoulder circumferential groove, a maximum groove width part forming the maximum groove width of the first shoulder lateral groove within the ground contact surface of the first shoulder land part, and an outer part outside the first tread end in the tire axial direction, The groove width at the inner end and the groove width of the first shoulder lateral groove on the first tread end are each smaller than the maximum groove width, The outer part has a groove width that decreases toward the outside in the tire axial direction, The first shoulder lateral groove includes an edge on one side in the tire circumferential direction and an edge on the other side in the tire circumferential direction, Chamfered parts are respectively continuous with the one-side edge and the other-side edge, The chamfered part includes an inclined surface obliquely extending from the edge, The chamfered part continuous with the one-side edge extends from the inner end of the first shoulder lateral groove to before the first tread end. a tire. **Claim 6**: A tire having a tread portion, wherein the tread portion includes a plurality of circumferential grooves continuously extending in the tire circumferential direction between a first tread end and a second tread end, and a plurality of land portions divided by the plurality of circumferential grooves; the plurality of circumferential grooves includes a first shoulder circumferential groove disposed closest to the first tread end side; the plurality of land portions includes the first tread end and a first shoulder land portion divided by the first shoulder circumferential groove; a plurality of first shoulder transverse grooves extending from the first shoulder circumferential groove to a position beyond the first tread end are provided in the first shoulder land portion; at least one of the first shoulder transverse grooves includes an inner end communicating with the first shoulder circumferential groove, a maximum groove width portion forming a maximum groove width of the first shoulder transverse groove within the ground contact surface of the first shoulder land portion, and an outer portion outside the tire axial direction relative to the first tread end; the groove width at the inner end and the groove width of the first shoulder transverse groove on the first tread end are each smaller than the maximum groove width; the outer portion has a groove width that decreases toward the outside in the tire axial direction; the first shoulder transverse groove includes an edge on one side in the tire circumferential direction and an edge on the other side in the tire circumferential direction; chamfered portions are respectively continuous with the one-side edge and the other-side edge; the chamfered portion includes an inclined surface obliquely extending from the edge; the one-side edge linearly extends from the inner end to the maximum groove width portion; the chamfered portion continuous with the one-side edge extends with a constant width from the inner end to the maximum groove width portion; a tire. **Claim 7**: The tire according to claim 5 or 6, wherein the first shoulder transverse groove further includes an inner portion extending outward in the tire axial direction with a constant groove width from the inner end. The chamfered portion continuous with the other-side edge is disposed at least in the inner portion and the maximum groove width portion. **Claim 8**: The tire according to any one of claims 5 to 7, wherein the chamfered portion continuous with the other-side edge extends from the maximum groove width portion to a position beyond the first tread end. **Claim 9**: The tire according to any one of claims 1 to 8, wherein the groove width at the inner end is 50% to 70% of the maximum groove width. **Claim 10**: The first shoulder transverse groove includes an outer end in the tire axial direction. The groove width at the outer end is 10% to 30% of the maximum groove width, the tire according to any one of claims 1 to 9.

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