Tire

Abstract

To provide a tire capable of improving wet braking performance while retaining drainage performance in the tread width direction.SOLUTION: A tire has a tread part 2 whose rotation direction R is designated. The tread part 2 includes a first tread end T1, a first inclined groove 3, and a first land part 5. At least one penetrating sipe 35 penetrating into the first land part 5 in the tire circumferential direction is disposed in the one first land part 5. The penetrating sipe 35 includes a sipe body part 36 extending from the tread of the first land part 5 to the inside in the tire radial direction, and a widening part 37 continuing to the inside in the tire radial direction of the sipe body part 36 and having a width larger than that of the sipe body part 36.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Patent Document 1 below proposes a tire in which a plurality of inclined grooves extending from the tread edge to near the tire equator are provided in the tread portion, and a plurality of inclined land portions divided by the inclined grooves are provided. Further, a plurality of sipes are provided in the inclined land portions.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a tire such as that of Patent Document 1, although drainage performance in the tread width direction can be expected to some extent due to the plurality of inclined grooves, the drainage performance in the tire circumferential direction tends to deteriorate. For this reason, there was room for further improvement in improving the braking performance (wet braking performance) on a wet road surface.

[0005] The present invention has been devised in view of the above actual situation, and the main object thereof is to provide a tire capable of improving wet braking performance while maintaining drainage performance in the tread width direction.

Means for Solving the Problems

[0006] The present invention relates to a tire having a tread portion with a specified rotational direction, wherein the tread portion includes a first tread end, a plurality of first inclined grooves extending obliquely in the leading side of the rotational direction from at least the first tread end to the vicinity of the tire equator, and a plurality of first land portions divided by the plurality of first inclined grooves. At least one of the plurality of first land portions is provided with at least one through sipe penetrating the first land portion in the tire circumferential direction. The through sipe includes a sipe main body portion extending radially inward of the tire from the tread surface of the first land portion, and a widened portion connected to the radially inner side of the sipe main body portion and having a width larger than that of the sipe main body portion.

Effects of the Invention

[0007] By adopting the above configuration, the tire of the present invention can improve the wet braking performance while maintaining the drainage performance in the tread width direction.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Best Mode for Carrying Out the Invention

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Although the drawings describe the features of the present invention, in order to assist in understanding the present invention, there may be exaggerated expressions or expressions different from the actual structural dimensional ratios. Also, throughout each embodiment, the same or common elements are given the same reference numerals, and duplicate explanations are omitted. FIG. 1 is a developed view of the tread portion 2 of the tire (hereinafter, may be simply referred to as "tire") 1 of the present embodiment. As shown in FIG. 1, the tire 1 of the present embodiment is a passenger car tire and is an all-season tire assuming driving not only on a dry road surface but also on a snowy road surface. However, the tire 1 of the present invention is not limited to such a mode, and for example, it may be a heavy-duty tire.

[0010] The tire 1 of the present invention has a tread portion 2 in which the rotation direction R is specified. The rotation direction R is indicated by characters or symbols on, for example, a sidewall portion (not shown).

[0011] The tread portion 2 of the tire 1 of the present embodiment includes a first tread end T1 and a second tread end T2. In each figure of this specification, the tread end on the left side of the tire equator C is taken as the first tread end T1, and the tread end on the right side of the tire equator C is taken as the second tread end T2. The tread portion 2 includes a first tread portion 2A on the first tread end T1 side of the tire equator C and a second tread portion 2B on the second tread end T2 side of the tire equator C. The first tread portion 2A and the second tread portion 2B are substantially line-symmetric with respect to the tire equator C except for the points that are displaced in the tire circumferential direction. For this reason, each configuration of the first tread portion 2A can be applied to the second tread portion 2B.

[0012] The first tread end T1 and the second tread end T2 are 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 is grounded on a plane.

[0013] The "normal state" means that in the case of a pneumatic tire with various standards defined, the tire is rim-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 for which various standards are not defined or a non-pneumatic tire, the "normal state" means a standard usage state corresponding to the usage purpose of the tire and in an unloaded state. In this specification, unless otherwise specified, the dimensions, etc. of each part of the tire are values measured in the normal state. Further, in this specification, unless otherwise specified, known methods can be appropriately applied to the method of measuring the dimensions.

[0014] The "normal rim" is the rim defined for each tire in a standard system including the standards 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 standard system including the standards 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, in the case of a pneumatic tire with various standards defined, the load defined for each tire in a standard system including the standards 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". In the case of a tire for which various standards are not defined, the "normal load" refers to the maximum load applicable in using the tire in accordance with the above-mentioned standards.

[0017] The tread portion 2 includes a plurality of first inclined grooves 3 and a plurality of second inclined grooves 4. In FIG. 1, dots are applied to these grooves and the through longitudinal grooves 30 described later. The first inclined groove 3 extends at least from the first tread end T1 toward the tire equator and is inclined toward the leading side in the rotational direction R. The second inclined groove 4 extends at least from the second tread end T2 toward the tire equator and is inclined toward the leading side in the rotational direction R. The second inclined groove 4 has substantially the same configuration as the first inclined groove 3, and the configuration of the first inclined groove 3 can be applied to the second inclined groove 4.

[0018] From the viewpoint of ensuring wet performance, the groove width W1 of the first inclined groove 3 and the groove width W2 of the second inclined groove 4 are, for example, 3 mm or more, desirably 4.0 to 7.0 mm, and more desirably 4.5 to 6.0 mm. Also, the depth of these inclined grooves is, for example, 4.0 to 8.5 mm, and desirably 5.0 to 8.0 mm.

[0019] The first inclined groove 3 of the present embodiment extends from a position outside the tire axial direction with respect to the first tread end T1 (omitted in FIG. 1). Also, the first inclined groove 3 crosses the center position in the tire axial direction between the first tread end T1 and the tire equator C and extends to the vicinity of the tire equator C. Note that this configuration means that the distance in the tire axial direction from the inner end on the tire equator C side of the first inclined groove 3 to the tire equator C is 15% or less of the tread width TW. In a desirable aspect, the said distance from the inner end of the first inclined groove 3 to the tire equator C is made 10% or less of the tread width TW. The tread width TW corresponds to the distance in the tire axial direction from the first tread end T1 to the second tread end T2 in the said normal state.

[0020] The first inclined groove 3 of the present embodiment includes, for example, a transverse first inclined groove 3A that extends to a position beyond the tire equator C and a non - transverse first inclined groove 3B that does not cross the tire equator C and is interrupted. In the present embodiment, the transverse first inclined groove 3A and the non - transverse first inclined groove 3B are alternately provided in the tire circumferential direction. However, the present invention is not limited to such an aspect.

[0021] The tread portion 2 of the present invention includes a plurality of first land portions 5 divided by a plurality of first inclined grooves 3. In FIG. 2, an enlarged view of two first inclined grooves 3 and one first land portion 5 is shown. As shown in FIGS. 1 and 2, at least one of the plurality of first land portions 5 is provided with at least one through-sipe 35 that penetrates the first land portion 5 in the tire circumferential direction. Note that "penetrating in the tire circumferential direction" means that the through-sipe 35 communicates with both of the two first inclined grooves 3 sandwiching the first land portion 5. Therefore, the through-sipe 35 may be inclined with respect to the tire circumferential direction.

[0022] In this specification, the "sipe" means a recess having a longitudinal direction and including a region where two inner walls contact each other in a state where a normal load is applied to the ground contact surface. The sipe width (the interval between the two inner walls in the normal state) in the region is, for example, less than 1.5 mm, preferably 0.4 to 1.2 mm. Note that the sipe may partially include a region where the two inner walls do not contact each other in a state where a normal load is applied. Therefore, the sipe may include a widened portion or a chamfered portion described later.

[0023] FIG. 3 shows a cross-sectional view taken along line A-A in FIG. 2. As shown in FIG. 3, the through-sipe 35 includes a sipe main body portion 36 that extends radially inward in the tire radius direction from the tread surface 5s of the first land portion 5, and a widened portion 37 that is continuous with the radially inner side of the sipe main body portion 36 and has a width larger than that of the sipe main body portion 36. By adopting the above configuration, the tire 1 of the present invention can improve the wet braking performance while maintaining the drainage performance in the tread width direction. The reason is as follows.

[0024] As shown in Fig. 1, since the tire 1 of the present invention includes a plurality of first inclined grooves 3, excellent drainage performance in the tread width direction can be exhibited. Further, as shown in Fig. 3, the through sipe 35 including the widened portion 37 can improve the drainage performance in the tire circumferential direction while maintaining the rigidity of the tread portion 2 (shown in Fig. 1), and thus can improve the wet braking performance. Further, the through sipe 35 having the widened portion 37 can maintain the water absorption performance even when the tread portion 2 is worn to some extent, and can exhibit excellent wet braking performance until the widened portion 37 appears on the ground contact surface.

[0025] 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 invention 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 invention 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.

[0026] As shown in Fig. 1, the inner end of the first inclined groove 3 on the tire equator C side communicates with the second inclined groove 4. In a desirable aspect, a pair of adjacent transverse first inclined grooves 3A and non-transverse first inclined grooves 3B in the tire circumferential direction communicate with the same second inclined groove 4. Similarly, the second inclined groove 4 communicates with the first inclined groove 3. Thereby, the drainage performance near the tire equator C is improved, and excellent wet braking performance is exhibited.

[0027] As shown in FIG. 2, the first inclined groove 3 includes an inner groove portion 3c on the tire equator C side, an outer groove portion 3a on the first tread end T1 side, and a central groove portion 3b connecting the inner groove portion 3c and the outer groove portion 3a. The inner groove portion 3c, the outer groove portion 3a, and the central groove portion 3b each extend linearly and have different angles with respect to the tire circumferential direction. In a preferred embodiment, the angle of the first inclined groove 3 with respect to the tire axial direction increases toward the tire equator C side. Such a first inclined groove 3 can provide frictional force in multiple directions and further enhance wet performance.

[0028] The outer groove portion 3a extends at least inward in the tire axial direction from the first tread end T1. The angle θ1 of the outer groove portion 3a with respect to the tire axial direction is, for example, 10° or less. The outer groove portion 3a of the present embodiment extends parallel to the tire axial direction.

[0029] The angle θ2 of the central groove portion 3b with respect to the tire axial direction is larger than the angle θ1 of the outer groove portion 3a with respect to the tire axial direction. The angle θ2 of the central groove portion 3b is, for example, 25 - 35°. Also, the angle θ3 of the inner groove portion 3c with respect to the tire axial direction is larger than the angle θ2 of the central groove portion 3b with respect to the tire axial direction. The angle θ3 of the inner groove portion 3c is, for example, 40 - 50°. The first inclined groove 3 having such an outer groove portion 3a, central groove portion 3b, and inner groove portion 3c can exhibit excellent drainage performance in the tread width direction.

[0030] As shown in FIG. 1, the distance L1 in the tire axial direction from the tire equator C to the intersection 41 of the inner groove portion 3c and the central groove portion 3b is 10% - 25% of the tread width TW (shown in FIG. 1). Note that the intersection 41 means a position where the angle of the tangent line of the groove center line of the first inclined groove 3 is the intermediate angle between the inner groove portion 3c and the central groove portion 3b.

[0031] The distance L2 in the tire axial direction from the tire equator C to the intersection 42 between the central groove portion 3b and the outer groove portion 3a is 30% to 45% of the tread width TW (shown in FIG. 1). The intersection 42 means a position where the angle of the tangent line of the groove center line of the first inclined groove 3 is the intermediate angle between the central groove portion 3b and the outer groove portion 3a. With such an arrangement of each groove portion, the wet performance and the wear resistance performance are improved in a well-balanced manner.

[0032] As shown in FIG. 1, in the present embodiment, the first land portions 5 provided with the through sipes 35 and the first land portions 5 not provided with the through sipes 35 are alternately arranged in the tire circumferential direction. However, the present invention is not limited to such an aspect, and the through sipes 35 may be arranged on each of the first land portions 5.

[0033] As shown in FIG. 2, the through sipes 35 are located on the tire equator C side rather than at the central position in the tire axial direction between the first tread end T1 and the tire equator C. As a desirable aspect, at least one end of the through sipes 35 communicates with the inner groove portion 3c of the first inclined groove 3. In a more desirable aspect, both ends of the through sipes 35 communicate with the inner groove portion 3c. Further, the through sipes 35 are not arranged on the tire equator C. Thereby, the distance between the through sipes 35 and the tire equator C becomes appropriate, and the wet performance and the wear resistance performance are improved in a well-balanced manner.

[0034] The through sipes 35 extend linearly in a tread plane view. Further, the through sipes 35 are arranged to be inclined at an angle of 30 to 50° with respect to the tire circumferential direction, for example. Thereby, the angle θ4 between the through sipes 35 and the first inclined groove 3 communicating with the leading side in the rotation direction R of the through sipes 35 is 75 to 105°. Such through sipes 35 provide frictional force in a well-balanced manner in the tire axial direction and the tire axial direction.

[0035] As shown in FIG. 1, the end of the through-sipe 35 on the tire equator C side is positioned to face the inner end of the second inclined groove 4 on the tire equator C side. Specifically, in a tread plane view, the end of the through-sipe 35 overlaps with the region where the second inclined groove 4 is virtually extended in its longitudinal direction. As a more desirable embodiment, in this embodiment, in a tread plane view, the entire through-sipe 35 overlaps with the virtually extended region. Thereby, the second inclined groove 4 and the through-sipe 35 can cooperate to enhance drainage performance, and the wet braking performance is further improved.

[0036] As shown in FIG. 3, the sipe body portion 36 of the through-sipe 35 extends linearly in parallel with the tire radial direction from the tread surface 5s of the first land portion 5 without passing through a chamfered portion or the like. The total depth d5 of the through-sipe 35 is 60% - 95% of the maximum depth of the first inclined groove 3. The length L3 of the sipe body portion 36 in the tire radial direction is 50% - 80% of the maximum depth of the first inclined groove 3. Also, the width W3 of the sipe body portion 36 is 0.4 - 0.8 mm. Such a sipe body portion 36 can enhance the wet braking performance while maintaining the rigidity of the first land portion 5.

[0037] The widened portion 37 forms the bottom of the through-sipe 35. Also, the widened portion 37 has a substantially semi-circular contour inside the communication portion with the sipe body portion 36. Also, the widened portion 37 extends in the longitudinal direction of the through-sipe 35 while maintaining the contour. The length L4 of the widened portion 37 in the tire radial direction is 10% - 25% of the maximum depth of the first inclined groove 3. The maximum width W4 of the widened portion 37 is 2.5 - 4.0 times the width W3 of the sipe body portion 36. Such a widened portion 37 can enhance the wet braking performance while suppressing vulcanization molding defects.

[0038] FIG. 4 shows an enlarged view of the first land portion 5. FIG. 5 shows a cross-sectional view taken along line B - B of FIG. 4. As shown in FIGS. 4 and 5, the first land portion 5 includes a tread surface 5s, a first side wall 11 on the leading side in the rotational direction R, and a second side wall 12 on the trailing side in the rotational direction R.

[0039] At least one of the plurality of first land portions 5 is provided with at least one recess 15 in which the first side wall 11 is locally recessed. This recess 15 opens at the tread surface 5s. Such a recess 15 can form a hard snow column by the recess 15 when the first land portion 5 contacts the ground. Further, excellent snow traction is exhibited when the snow column is sheared.

[0040] As shown in FIG. 5, in the plan view of the first land portion 5, it is desirable that the maximum recess amount da in the direction orthogonal to the longitudinal direction of the first inclined groove 3 of the recess 15 is 80% to 150% of the width W4 (shown in FIG. 3) of the widened portion 37 of the through-cavity 35. Further, the maximum recess amount da is, for example, 1.0 to 2.5 mm, and preferably 1.5 to 2.0 mm. Thereby, the wear progress between the periphery of the recess 15 and the periphery of the through-cavity 35 becomes uniform, and the uneven wear resistance performance is improved.

[0041] As shown in FIG. 4, it is desirable that a plurality of recesses 15 are provided in the first land portion 5. In the present embodiment, for each of the plurality of recesses 15 provided in one first land portion 5, the maximum recess amount da is within the above-described range. Thereby, the above-described effects are surely exhibited.

[0042] In the present embodiment, the plurality of recesses 15 provided in one first land portion 5 are composed of a first recess 16, a second recess 17, and a third recess 18. The first recess 16 is provided closest to the first tread end T1 among these plurality of recesses 15, and in the present embodiment, it is in contact with the outer groove portion 3a (shown in FIG. 2) of the first inclined groove 3. The second recess 17 is located closer to the tire equator C side than the first recess 16. The third recess 18 is located closer to the tire equator C side than the second recess 17. The second recess 17 and the third recess 18 are each in contact with the central groove portion 3b (shown in FIG. 2) of the first inclined groove 3.

[0043] The first recess 16 is preferably, for example, located at a distance of 5.0 mm or more from the first tread end T1 and the through longitudinal groove 30 described later. Further, the second recess 17 is preferably located at a distance of 5.0 mm or more from the through longitudinal groove 30. Further, the third recess 18 is preferably located at a distance of 5.0 mm or more from the second recess 17. Thereby, uneven wear of the first land portion 5 is suppressed.

[0044] Among the plurality of recesses 15 provided in one first land portion 5, the maximum length in the longitudinal direction of the recess 15 provided closest to the first tread end T1 side (in this embodiment, it is the first recess 16.) is greater than the maximum length in the longitudinal direction of the other recesses 15 (in this embodiment, they are the second recess 17 and the third recess 18). Specifically, the maximum length L5 of the first recess 16 is 150% to 250% of the maximum length L6 of the second recess 17. Further, the maximum length L6 of the second recess 17 is 80% to 120% of the maximum length L7 of the third recess 18, and in this embodiment, they are the same. Such a plurality of recesses 15 helps to enhance the handling stability and snow performance in a well-balanced manner.

[0045] Further, the maximum length L5 of the first recess 16 is, for example, 3.0 to 12.0 mm, preferably 5.0 to 10.0 mm. The maximum length L6 of the second recess 17 and the maximum length L7 of the third recess 18 are, for example, 3.0 to 8.0 mm, preferably 4.0 to 7.0 mm.

[0046] The opening shape of the recess 15 on the tread surface 5s of the first land portion 5 is, for example, trapezoidal. However, the present invention is not limited to such a shape, and the opening shape may be triangular or semi-circular.

[0047] From the same viewpoint, as shown in FIG. 5, the maximum depth d2 of the recess 15 from the tread surface 5s is 50% to 80% of the maximum depth d1 of the first inclined groove 3.

[0048] At least a part of the first land portion 5 has a chamfered portion 23 formed between the second sidewall 12 and the tread surface 5s. The chamfered portion 23 is configured as a minute inclined surface 23s arranged so that the sharp corner formed by the second sidewall 12 and the tread surface 5s is removed. In the present embodiment, since such a chamfered portion 23 is formed on the second sidewall 12 side, distortion of the tread surface during braking on a dry road surface is suppressed, the substantial contact area increases, and the braking performance on a dry road surface is improved.

[0049] The angle θ5 of the inclined surface 23s of the chamfered portion 23 with respect to the tire normal is, for example, 30 to 60°, preferably 40 to 50°. Further, the width W5 (shown in FIG. 4) of the inclined surface 23s in the plan view of the first land portion 5 is, for example, 0.5 to 2.0 mm, preferably 1.0 to 1.5 mm. Further, the depth d3 of the inclined surface 23s is, for example, 0.5 to 2.5 mm, preferably 1.0 to 2.0 mm.

[0050] As shown in FIG. 2, in the present embodiment, the above-described chamfered portion 23 is formed at a portion inside the first land portion 5 and in contact with the outer groove portion 3a and the central groove portion 3b of the first inclined groove 3. Thereby, since the chamfered portion 23 is arranged in a region where the contact pressure increases during braking, the above-described effects can be surely obtained.

[0051] In the plan view of the first land portion 5, the area of the chamfered portion 23 is 10% to 15% of the area of the tread surface 5s of one first land portion 5. Thereby, the handling stability and the snow performance are improved in a well-balanced manner.

[0052] The second sidewall 12 includes a non-chamfered portion 24 that is continuous with the tread surface 5s without passing through the chamfered portion 23. The non-chamfered portion 24 is arranged at a portion in contact with the inner groove portion 3c in the second sidewall 12. Thereby, a high edge effect can be expected in a region close to the tire equator C. For this reason, excellent snow traction can be expected.

[0053] As shown in FIG. 4, at least one inclined sipe 25 extending along the longitudinal direction of the first land portion 5 is provided on the first land portion 5. In the present embodiment, one inclined sipe 25 is provided on one first land portion 5.

[0054] The inclined sipe 25 extends along the first inclined groove 3 (shown in FIG. 2) from the first tread edge T1 to the end of the first land portion 5 on the tire equator C side. In a preferred embodiment, when the first land portion 5 is divided into three equal parts in a direction perpendicular to the longitudinal direction by two virtual lines extending along the longitudinal direction of the first inclined groove 3, the inclined sipe 25 is provided in the central region. Such an inclined sipe 25 can enhance wet performance while suppressing uneven wear of the first land portion 5.

[0055] The inclined sipe 25 includes an outer sipe portion 25a, a central sipe portion 25b, and an inner sipe portion 25c. The outer sipe portion 25a extends linearly at least from the first tread edge T1 inward in the tire axial direction. The outer sipe portion 25a of the present embodiment extends along the outer groove portion 3a (shown in FIG. 2) of the first inclined groove 3, and in a preferred embodiment, they are parallel. Also, the length of the outer sipe portion 25a is set to be 80% to 120% of the length of the outer groove portion 3a.

[0056] The central sipe portion 25b extends linearly connected to the inner side of the outer sipe portion 25a in the tire axial direction. The central sipe portion 25b extends along the central groove portion 3b (shown in FIG. 2) of the first inclined groove 3, and in a preferred embodiment, they are parallel. Also, the length of the central sipe portion 25b is set to be 80% to 120% of the length of the central groove portion 3b.

[0057] The inner side rib portion 25c extends linearly connected to the inner side in the tire axial direction of the central side rib portion 25b. The inner side rib portion 25c extends along the inner groove portion 3c (shown in FIG. 2) of the first inclined groove 3, and in a desirable embodiment, they are parallel. Also, the length of the inner side rib portion 25c is set to be 80% to 120% of the length of the inner groove portion 3c. Such an inclined side rib 25 including the outer side rib portion 25a, the central side rib portion 25b, and the inner side rib portion 25c can surely suppress uneven wear of the first land portion 5.

[0058] FIG. 6 shows a cross-sectional view taken along the line C-C of FIG. 4. As shown in FIG. 6, the inclined side rib 25 is provided with a chamfered portion 28 at the edge on the leading side in the rotational direction R. The chamfered portion 28 is configured as a minute inclined surface arranged so that the sharp corner formed by the tread surface 5s of the first land portion 5 and the side rib wall 25w is removed. The angle of this inclined surface with respect to the tire normal is, for example, 40 to 50°. Such a chamfered portion 28 can enhance the braking performance on a dry road surface.

[0059] In a desirable embodiment, the inclined side rib 25 is not provided with a chamfered portion at the edge on the trailing side in the rotational direction R. Thereby, the edge on the trailing side of the inclined side rib 25 can exhibit a large frictional force during snow driving, and snow traction is improved.

[0060] As shown in FIG. 4, the above-described chamfered portion 28 is provided on the outer side rib portion 25a and the central side rib portion 25b. On the other hand, the inner side rib portion 25c is not provided with a chamfered portion on either of the edges on both sides. Thereby, the handling stability on a dry road surface and the snow traction are improved in a well-balanced manner.

[0061] As shown in FIG. 2, at least one through longitudinal groove 30 is provided in the first land portion 5 of the present embodiment to connect two first inclined grooves 3 adjacent to each other in the tire circumferential direction. In the present embodiment, one through longitudinal groove 30 is provided in one first land portion 5. The through longitudinal groove 30 of the present embodiment connects the central groove portions 3b of the first inclined grooves 3 adjacent to each other in the tire circumferential direction. The communication position of the through longitudinal groove 30 with respect to the central groove portion 3b is on the first tread end T1 side rather than the center position in the longitudinal direction of the central groove portion 3b. Such a through longitudinal groove 30 makes it easier to appropriately deform its periphery and can prevent snow from clogging in the first inclined groove 3. Thereby, excellent snow performance is continuously exhibited.

[0062] The through longitudinal groove 30 is inclined in a direction opposite to the central groove portion 3b with respect to the tire axial direction. The angle of the through longitudinal groove 30 with respect to the tire circumferential direction is, for example, 5 to 15°. Such a through longitudinal groove 30 can exert a large snow column shearing force in the tire axial direction during snow driving.

[0063] FIG. 7 shows a cross-sectional view taken along line D-D of FIG. 4. As shown in FIG. 7, the through longitudinal groove 30 includes a groove bottom narrow groove 31 that opens at its bottom surface and extends in the tire radial direction. Such a groove bottom narrow groove 31 helps to further improve wet performance.

[0064] As shown in FIG. 1, the land ratio of the tread portion 2 of the present embodiment is, for example, 50% to 65%, preferably 55% to 60%. Thereby, the steering stability and the snow traction are improved in a well-balanced manner. In the present specification, the "land ratio" corresponds to the ratio of the actual contact area to the contact area in a state where all the grooves and sipes of the tread portion 2 are filled.

[0065] FIG. 8 shows a developed view of the tread portion 2 of the tire 1 according to another embodiment of the present invention. As shown in FIG. 8, in this embodiment, one crown circumferential groove 7 that linearly extends continuously in the tire circumferential direction is provided on the tire equator C. Further, the first inclined groove 3 and the second inclined groove 4 communicate with the crown circumferential groove 7, respectively. In this embodiment, the crown circumferential groove 7 enhances the drainage performance in the tire circumferential direction, and the wet braking performance is further improved. Note that the embodiment shown in FIG. 8 is substantially the same as the embodiment shown in FIG. 1 except for the above-described crown circumferential groove 7 and includes the above-described respective configurations.

[0066] FIG. 9 shows a developed view of the tread portion 2 of the tire 1 according to another embodiment of the present invention. This embodiment is obtained by making the following changes to the tire 1 shown in FIG. 1. As shown in FIG. 9, in this embodiment, the first land portion 5 has a first corner portion 5a, and a chamfered portion 45 is provided at the first corner portion 5a. The first corner portion 5a is a corner portion formed at a portion where the first inclined groove 3 and the second inclined groove 4 are continuous, and means a corner portion that protrudes toward one side in the tire circumferential direction (in this embodiment, the leading side in the rotation direction R).

[0067] FIG. 10 shows an enlarged cross-sectional view of the first corner portion 5a provided with the chamfered portion 45. As shown in FIG. 10, the chamfered portion 45 of the first corner portion 5a has an inclined surface 46 that is inclined at an angle θ6 of 30 to 50° with respect to the tire normal. The chamfered portion 45 can effectively suppress the uneven wear of the first land portion 5. Further, since the inclined surface 46 comes into contact with the ground during braking by forming such a chamfered portion 45 at the first corner portion 5a, the substantial contact area increases. Therefore, the braking performance on a dry road surface and a wet road surface can be improved.

[0068] As shown in FIG. 9, the maximum width W5 of the chamfered portion 45 in the tire axial direction is, for example, 3 to 5 mm. The angle of the ridge line 45a formed by the tread surface 5s of the first land portion 5 and the inclined surface 46 (shown in FIG. 10) of the chamfered portion 45 with respect to the tire circumferential direction is, for example, 80 to 90°. Also, as shown in FIG. 10, the length L8 of the inclined surface 46 of the chamfered portion 45 in the tire circumferential direction is 3 to 5 mm. Further, the length L9 of the inclined surface 46 of the chamfered portion 45 in the tire radial direction is 50% or less of the maximum depth of the first inclined groove 3. Such a chamfered portion 45 can exhibit the above-described effects while maintaining the rubber volume of the first land portion 5.

[0069] As shown in FIG. 9, the second corner portion 5b of the first land portion 5 of this embodiment does not have the above-described chamfered portion. The second corner portion 5b is a corner portion formed at the portion where the first inclined groove 3 and the second inclined groove 4 are continuous, and means a corner portion that protrudes toward the second tread end T2 side. Thereby, the second corner portion 5b can provide a large frictional force in the tire axial direction and can exhibit excellent turning performance on dry and wet road surfaces.

[0070] FIG. 11 shows a developed view of the tread portion 2 of the tire 1 according to another embodiment of the present invention. This embodiment is obtained by adding the above-described chamfered portion 45 to the first land portion 5 of the tire 1 shown in FIG. 8. Also in this embodiment, the above-described effects can be obtained by the chamfered portion.

[0071] As described above, the tire according to one embodiment of the present invention has been described in detail. However, the present invention is not limited to the above specific embodiments and can be implemented in various modes.

Example

[0072] As an example, a pneumatic tire of size 205 / 55R16 having the basic pattern of FIG. 1 was prototyped. As a comparative example, a tire composed only of a sipe body portion that extends with a constant width without a through-sipe having a widened portion was prototyped. These test tires have substantially the same configuration except for the matters described above. For each test tire (when new and at 20% wear), the drainage performance and wet braking performance on a wet road surface were tested. The common specifications and test methods for each test tire are as follows. Mounting rim: 16×6.5 Tire internal pressure: 250 kPa for all wheels Test vehicle: A front-wheel drive vehicle with a displacement of 2000 cc Tire mounting position: All wheels

[0073] <Drainage performance on a wet road surface> The test vehicle was driven on a wet road surface, and the speed at which the hydroplaning phenomenon occurred was measured. The result is the exponentiation of the speed, and the larger the numerical value, the better the drainage performance on the wet road surface.

[0074] <Wet braking performance> The test vehicle was suddenly braked on a wet road surface, and the braking distance was measured. The result is the exponentiation of the reciprocal of the braking distance, and the larger the numerical value, the better the wet braking performance. The test results are shown in Table 1.

[0075]

Table 1

[0076] As shown in Table 1, as a result of the test, it was confirmed that the tires of the example improved the drainage performance and wet braking performance on the wet road surface by 3 points compared to the tires of the comparative example. Also, it was confirmed that the tires of the example could maintain the drainage performance and wet braking performance on the wet road surface even when the tread portion was worn by 20%.

[0077] [Appendix] The present invention includes the following aspects.

[0078] [Invention 1] A tire having a tread portion with a specified rotational direction, The tread portion includes a first tread end, a plurality of first inclined grooves that extend obliquely toward the leading side in the rotational direction from at least the first tread end to the vicinity of the tire equator, and a plurality of first land portions divided by the plurality of first inclined grooves. At least one of the plurality of first land portions is provided with at least one through-sipe that penetrates the first land portion in the tire circumferential direction. The through-sipe includes a sipe main body portion that extends from the tread surface of the first land portion inward in the tire radial direction, and a widened portion that is continuous with the sipe main body portion inward in the tire radial direction and has a width larger than that of the sipe main body portion. Tire. [Invention 2] The length of the sipe main body portion in the tire radial direction is 50% to 80% of the maximum depth of the first inclined groove, the tire according to Invention 1. [Invention 3] The maximum width of the widened portion is 2.5 to 4.0 times the width of the sipe main body portion, the tire according to Invention 1 or 2. [Invention 4] The first inclined groove includes an inner groove portion on the tire equator side, an outer groove portion on the first tread end side, and a central groove portion that is continuous with the inner groove portion and the outer groove portion. The inner groove portion, the outer groove portion, and the central groove portion each extend linearly and have different angles with respect to the tire circumferential direction, the tire according to any one of Inventions 1 to 3. [Invention 5] The distance in the tire axial direction from the tire equator to the intersection of the inner groove portion and the central groove portion is 10% to 25% of the tread width, the tire according to Invention 4. [Invention 6] The distance in the tire axial direction from the tire equator to the intersection of the central groove portion and the outer groove portion is 30% to 45% of the tread width, the tire according to Invention 4 or 5. [The present invention 7] The tire according to any one of claims 4 to 6 of the present invention, wherein one end of the through groove communicates with the inner groove portion. [The present invention 8] The angle of the central groove portion with respect to the tire axis direction is larger than the angle of the outer groove portion with respect to the tire axis direction, The tire according to any one of claims 4 to 7 of the present invention, wherein the angle of the inner groove portion with respect to the tire axis direction is larger than the angle of the central groove portion with respect to the tire axis direction. [The present invention 9] The tire according to any one of claims 1 to 8 of the present invention, wherein the angle between the through groove and the first inclined groove communicating with the leading side in the rotational direction of the through groove is 75 to 105°. [The present invention 10] The tread portion further includes a second tread end and a plurality of second inclined grooves that extend obliquely toward the leading side in the rotational direction from at least the second tread end to the vicinity of the tire equator. The through groove is inclined with respect to the tire circumferential direction. The tire according to any one of claims 1 to 9 of the present invention, wherein the end portion of the through groove on the tire equator side is positioned to face the inner end on the tire equator side of the plurality of second inclined grooves. [The present invention 11] The tread portion further includes a second tread end and a plurality of second inclined grooves that extend obliquely toward the leading side in the rotational direction from at least the second tread end to the vicinity of the tire equator. The first inclined groove communicates with the second inclined groove. The first land portion has a first corner portion that protrudes toward one side in the tire circumferential direction at a portion where the first inclined groove and the second inclined groove are continuous. The first corner portion has a chamfered portion including an inclined surface inclined with respect to the tire normal. The tire according to any one of claims 1 to 10 of the present invention, wherein the first corner portion protrudes toward the leading side in the rotational direction. [The present invention 12] The maximum width of the chamfered portion in the tire axis direction is 3 to 5 mm. The length in the tire circumferential direction of the inclined surface of the chamfered portion is 3 to 5 mm, The length in the tire radial direction of the chamfered portion is 50% or less of the maximum depth of the first inclined groove. The tire according to Invention 11 of the present invention. [Invention 13] The angle with respect to the tire circumferential direction of the ridge line formed by the tread surface of the first land portion and the inclined surface of the chamfered portion is 80 to 90°. The tire according to Invention 11 or 12 of the present invention. [Invention 14] The first land portion has a second corner portion that protrudes toward the second tread end at a portion where the first inclined groove and the second inclined groove are continuous. The chamfered portion is not provided at the second corner portion. The tire according to any one of Inventions 11 to 13 of the present invention.

Explanation of reference numerals

[0079] 2 Tread portion 3 First inclined groove 5 First land portion 35 Through sip 36 Sip body portion 37 Widthening portion T1 First tread end

Claims

1. A tire having a tread portion with a specified rotational direction, wherein the tread portion includes a first tread edge, a plurality of first inclined grooves extending obliquely in the leading side in the rotational direction from at least the first tread edge to the vicinity of the tire equator, and a plurality of first land portions separated by the plurality of first inclined grooves, at least one of the plurality of first land portions is provided with at least one through-sipe penetrating the first land portion in the tire circumferential direction, the through-sipe includes a sipe main body portion extending radially inward from the tread surface of the first land portion, and a widened portion connected to the radially inner side of the sipe main body portion and having a width larger than that of the sipe main body portion, a tire.

2. The tire according to claim 1, wherein the length of the sipe main body portion in the tire radial direction is 50% to 80% of the maximum depth of the first inclined groove.

3. The tire according to claim 2, wherein the maximum width of the widened portion is 2.5 to 4.0 times the width of the sipe main body portion.

4. The first inclined groove includes an inner groove portion on the tire equator side, an outer groove portion on the first tread edge side, and a central groove portion connecting the inner groove portion and the outer groove portion, wherein the inner groove portion, the outer groove portion, and the central groove portion each extend linearly and have different angles with respect to the tire circumferential direction, the tire according to any one of claims 1 to 3.

5. The tire according to claim 4, wherein the distance in the tire axial direction from the tire equator to the intersection of the inner groove portion and the central groove portion is 10% to 25% of the tread width.

6. The tire according to claim 4, wherein the distance in the tire axial direction from the tire equator to the intersection of the central groove portion and the outer groove portion is 30% to 45% of the tread width.

7. The tire according to claim 4, wherein one end of the through-sipe communicates with the inner groove portion.

8. The angle of the central groove portion with respect to the tire axial direction is larger than the angle of the outer groove portion with respect to the tire axial direction, the angle of the inner groove portion with respect to the tire axial direction is larger than the angle of the central groove portion with respect to the tire axial direction, the tire according to claim 4.

9. The tire according to any one of claims 1 to 3, wherein the angle between the through-sipe and the first inclined groove communicating with the leading side in the rotational direction of the through-sipe is 75 to 105°.

10. The tread portion further includes a second tread edge and a plurality of second inclined grooves that are inclined and extend from at least the second tread edge to the vicinity of the tire equator on the leading side in the rotational direction. The through sipe is inclined with respect to the tire circumferential direction. The tire according to any one of claims 1 to 3, wherein an end portion of the through sipe on the tire equator side is positioned so as to face an inner end on the tire equator side of the plurality of second inclined grooves.

11. The tread portion further includes a second tread edge and a plurality of second inclined grooves that are inclined and extend from at least the second tread edge to the vicinity of the tire equator on the leading side in the rotational direction. The first inclined groove communicates with the second inclined groove. The first land portion has a first corner portion that protrudes toward one side in the tire circumferential direction at a portion where the first inclined groove and the second inclined groove are continuous. The first corner portion has a chamfered portion including an inclined surface inclined with respect to the tire normal. The tire according to any one of claims 1 to 3, wherein the first corner portion protrudes toward the leading side in the rotational direction.

12. The maximum width of the chamfered portion in the tire axial direction is 3 to 5 mm. The length of the inclined surface of the chamfered portion in the tire circumferential direction is 3 to 5 mm. The tire according to claim 11, wherein the length of the chamfered portion in the tire radial direction is 50% or less of the maximum depth of the first inclined groove.

13. The angle of the ridge line formed by the tread surface of the first land portion and the inclined surface of the chamfered portion with respect to the tire circumferential direction is 80 to 90°. The tire according to claim 11.

14. The first land portion has a second corner portion that protrudes toward the second tread edge side at a portion where the first inclined groove and the second inclined groove are continuous. The tire according to claim 11, wherein the chamfered portion is not provided at the second corner portion.

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