JP6880971B2 - tire - Google Patents

Description

The present invention provides a tire capable of exhibiting excellent on-snow performance while maintaining steering stability on a dry road surface.

For example, Patent Document 1 below proposes a tire for winter. The tread portion of the tire of Patent Document 1 is provided with a plurality of inclined grooves extending obliquely from the tread end toward the equator side of the tire, and a plurality of inclined land portions divided between the inclined grooves. The inclined land portion is provided with a plurality of joint grooves communicating between the inclined grooves. In the tire of Patent Document 1, the joint groove includes an inner joint groove arranged most on the equator side of the tire and an intermediate joint groove adjacent thereto.

Since a large contact pressure acts on the inner joint groove when traveling on snow, it tends to contribute significantly to traction on snow. However, in the tire of Patent Document 1, the inner joint groove extends along the tire circumferential direction, and there is a tendency that improvement in traction on snow due to the inner joint groove cannot be expected so much.

On the other hand, in a tire having an inclined groove and an inclined land portion as in Patent Document 1, when the angle of the joint groove with respect to the tire circumferential direction becomes large, the lateral rigidity of the block divided into the inclined groove and the joint groove decreases, and the dry road surface There was a problem that the steering stability was impaired.

Japanese Unexamined Patent Publication No. 2016-000578

The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a tire capable of exhibiting excellent on-snow performance while maintaining steering stability on a dry road surface.

The present invention is a tire having a tread portion, and the tread portion has a plurality of inclined grooves extending diagonally from a first tread end on one side in the tire axial direction toward the tire equatorial side, and in the tire circumferential direction. A plurality of inclined land portions divided between the adjacent inclined grooves are provided, and the inclined land portion is provided with a plurality of joint grooves communicating between the inclined grooves, and the joint groove is the most. An inner joint groove arranged on the equatorial side of the tire and at least one intermediate joint groove arranged adjacent to the first tread end side of the inner joint groove are included, and the intermediate joint groove is the inner joint groove. The angle with respect to the tire circumferential direction is smaller than the groove.

In the tire of the present invention, it is desirable that the inclined groove is curved so that the angle with respect to the tire axial direction gradually increases toward the tire equatorial side.

In the tire of the present invention, it is desirable that the intermediate joint groove has at least one bent portion.

In the tire of the present invention, it is desirable that the bent portion includes two that are convex in opposite directions to each other.

In the tire of the present invention, the joint groove includes an outer joint groove different from the intermediate joint groove arranged on the end side of the first tread, and the outer joint groove is more peripheral to the tire than the intermediate joint groove. It is desirable that the angle with respect to the direction is large.

In the tire of the present invention, it is desirable that the outer joint groove has a smaller angle with respect to the tire circumferential direction than the inner joint groove.

In the tire of the present invention, it is desirable that two intermediate joint grooves are provided between the inner joint groove and the outer joint groove.

In the tire of the present invention, it is desirable that the intermediate joint groove and the outer joint groove are inclined in the opposite direction to the inclined groove.

In the tire of the present invention, it is desirable that an outer lug groove extending from one of the adjacent inclined grooves and interrupted in the inclined land portion is provided between the outer joint groove and the first tread end.

In the tire of the present invention, it is desirable that the inclined groove is interrupted without crossing the tire equator, and is provided with a central lateral groove that branches off from the inclined groove and extends in the tire axial direction and crosses the tire equator.

In the tire of the present invention, it is desirable that the central lateral groove extends smoothly through the inclined groove so as to be smoothly continuous with the inner joint groove.

The tread portion of the tire of the present invention is divided between a plurality of inclined grooves extending diagonally from the first tread end on one side in the tire axial direction toward the tire equatorial side and the inclined grooves adjacent to each other in the tire circumferential direction. There are a plurality of sloping land areas. When traveling on snow, the inclined groove forms a long snow column extending diagonally with respect to the tire axial direction, and by shearing this, a large snow traction can be obtained.

The inclined land portion of the tire of the present invention is provided with a plurality of joint grooves communicating between the inclined grooves. The joint includes an inner joint most arranged on the equator side of the tire and at least one intermediate joint arranged adjacent to the first tread end side of the inner joint. The intermediate joint groove is formed so that the angle with respect to the tire circumferential direction is smaller than that of the inner joint groove.

Since a large contact pressure acts on the inner joint groove arranged on the equator side of the tire when traveling straight on snow, it contributes greatly to traction on snow. Therefore, by increasing the angle of the inner joint groove with respect to the tire circumferential direction, the inner joint groove can form a hard snow column together with the inclined groove, and thus can further enhance the traction on snow.

On the other hand, since the intermediate joint groove is provided on the first tread end side of the inner joint groove, a larger contact pressure than the inner joint groove acts on the intermediate joint groove when the tire is turning. In the present invention, paying attention to such a difference in contact pressure, the angle of the intermediate joint groove with respect to the tire circumferential direction is set small. As a result, while obtaining the snow column shearing force in the intermediate joint groove, the lateral rigidity of the blocks divided on both sides of the intermediate joint groove can be increased, and the steering stability on a dry road surface can be maintained.

As described above, the tire of the present invention can exhibit excellent on-snow performance while maintaining steering stability on a dry road surface.

It is a development view of the tread part of the tire of one Embodiment of this invention. It is an enlarged view of the 1st tread part of FIG. It is an enlarged view of the outline of the 1st intermediate joint groove. FIG. 2 is a sectional view taken along line AA of FIG. It is an enlarged view of the contour of the inclined groove, the central lateral groove and the joint groove. It is an enlarged view of the inclined land part. FIG. 6 is a cross-sectional view taken along the line BB of FIG. It is a development view of the tread part of the tire of another embodiment of this invention. It is a development view of the tread part of the tire of another embodiment of this invention. It is a development view of the tread part of the tire of the comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a developed view of the tread portion 2 of the tire 1 of the present embodiment. As shown in FIG. 1, the tire 1 of the present embodiment is suitably used as, for example, a winter pneumatic tire for a passenger car. In another aspect of the present invention, the tire 1 can be used, for example, as a pneumatic tire for heavy loads, a non-pneumatic tire in which pressurized air is not filled inside the tire, and the like.

The tire 1 of the present embodiment includes, for example, a directional pattern in which the rotation direction R is specified. The rotation direction R is indicated by characters or symbols on the sidewall portion (not shown), for example.

The tire 1 of the present embodiment has a tread portion 2 between a first tread end Te1 and a second tread end Te2. The tread portion 2 includes a first tread portion 2A between the tire equator C and the first tread end Te1 and a second tread portion 2B between the tire equator C and the second tread end Te2.

In the case of a pneumatic tire, the first tread end Te1 and the second tread end Te2 are at the most outer contact positions in the tire axial direction when a normal load is applied to the tire 1 in a normal state and the tire 1 touches a plane at a camber angle of 0 °. is there. The normal state is a state in which the tire is rim-assembled on the normal rim, the normal internal pressure is applied, and there is no load. In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in a normal state.

A "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, "standard rim" for JATMA, "Design Rim" for TRA, and ETRTO. If there is, it is "Measuring Rim".

"Regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum air pressure", for TRA, the table "TIRE LOAD LIMITS AT" The maximum value described in "VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

"Regular load" is the load defined for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum load capacity", for TRA, the table "TIRE LOAD LIMITS" The maximum value described in "AT VARIOUS COLD INFLATION PRESSURES", or "LOAD CAPACITY" for ETRTO.

The tread portion 2 is provided with a plurality of inclined grooves 10.

The inclined groove 10 includes, for example, a first inclined groove 10A provided in the first tread portion 2A and a second inclined groove 10B provided in the second tread portion 2B. The first inclined groove 10A extends obliquely from the first tread end Te1 toward the tire equator C side. The second inclined groove 10B extends obliquely from the second tread end Te2 toward the tire equator C side. The second inclined groove 10B has substantially the same configuration as the first inclined groove 10A. Therefore, unless otherwise specified, the configuration of the first inclined groove 10A can be applied to the second inclined groove 10B. When traveling on snow, each inclined groove 10 forms a long snow pillar extending diagonally with respect to the tire axial direction, and by shearing this, a large snow traction can be obtained.

In a desirable embodiment, the inclined grooves 10A and 10B are inclined from the tread ends Te1 and Te2 toward the tire equator C side toward the first-come-first-served side in the rotation direction R. However, the present invention is not limited to such an aspect.

FIG. 2 shows an enlarged view of the first tread portion 2A. As shown in FIG. 2, it is desirable that the inclined groove 10 is curved so that, for example, the angle θ1 with respect to the tire axial direction gradually increases toward the tire equator C side. The angle θ1 is preferably, for example, 0 to 80 °. Such an inclined groove 10 can exert a snow column shearing force also in the tire axial direction when traveling on snow.

The inclined groove 10 is interrupted without crossing the tire equator C, for example. The distance L1 in the tire axial direction from the inner end of the inclined groove 10 (meaning the inner end of the groove center line in the tire axial direction, and the same applies hereinafter) to the tire equatorial line is, for example, 2.0 of the tread width TW. It is preferably% to 7.0%. The tread width TW is the distance in the tire axial direction from the first tread end Te1 to the second tread end Te2 in the normal state.

It is desirable that the groove width of the inclined groove 10 gradually increases toward, for example, the first tread end Te1 side. The maximum groove width W1 of the inclined groove 10 is preferably, for example, 3.0% to 5.0% of the tread width TW. In the case of winter tires for passenger cars, the depth of the inclined groove 10 is, for example, 6.0 to 12.0 mm, preferably 8.1 to 9.1 mm.

The tread portion 2 of the present embodiment is provided with a central lateral groove 12. The central lateral groove 12 branches from the inclined groove 10 and extends in the tire axial direction and crosses the tire equator, for example. More specifically, the central lateral groove 12 includes a first central lateral groove 12A and a second central lateral groove 12B. The first central lateral groove 12A is inclined in the same direction as the first inclined groove 10A. The first central lateral groove 12A branches from the first inclined groove 10A, extends in the tire axial direction, and is connected to the second inclined groove 10B. The second central lateral groove 12B is inclined in the same direction as the second inclined groove 10B. The second central lateral groove 12B branches from the second inclined groove 10B, extends in the tire axial direction, and is connected to the first inclined groove 10A. The first central lateral groove 12A and the second central lateral groove 12B are alternately provided in the tire circumferential direction.

It is desirable that the central lateral groove 12 is arranged at an angle θ2 of 10 to 20 ° with respect to the tire axial direction, for example.

The tread portion 2 is provided with an inclined land portion 13. The inclined land portion 13 is divided between the inclined grooves 10 adjacent to each other in the tire circumferential direction. The inclined land portion 13 of the present embodiment includes, for example, a region divided between the first central lateral groove 12A and the second central lateral groove 12B.

As shown in FIG. 1, the inclined land portion 13 is divided between, for example, a first inclined land portion 13A divided among a plurality of first inclined grooves 10A and a plurality of second inclined grooves 10B. Includes the second inclined land portion 13B. The second inclined land portion 13B has substantially the same configuration as the first inclined land portion 13A. Therefore, unless otherwise specified, the configuration of the first inclined land portion 13A can be applied to the second inclined land portion 13B.

As shown in FIG. 2, the inclined land portion 13 is provided with a plurality of joint grooves 15 communicating between the inclined grooves 10.

The joint groove 15 includes an inner joint groove 16, at least one intermediate joint groove 17, and an outer joint groove 18 different from the intermediate joint groove 17 arranged on the side of the first tread end Te.

The inner joint groove 16 is arranged on the tire equator C side most among the plurality of joint grooves 15. The inner joint groove 16 is located, for example, on the tire equator C side of the center position (not shown) of the first tread portion 2A in the tire axial direction. In the inner joint groove 16 of the present embodiment, for example, the distance L2 from the outer end in the tire axial direction (meaning the outer end in the tire axial direction of the groove center line, and the same applies hereinafter) to the tire equatorial line C is a tread. It is desirable that the width is 0.10 to 0.14 times the width TW.

The inner joint groove 16 extends linearly, for example. The inner joint groove 16 is arranged at an angle θ3 of 80 to 90 ° with respect to the tire circumferential direction, for example. Such an inner joint groove 16 is useful for enhancing traction on snow. When the inner joint groove 16 is inclined with respect to the tire axial direction, it is desirable that the inner joint groove 16 is inclined in the opposite direction to the inclined groove 10.

The intermediate joint groove 17 is arranged adjacent to the first tread end Te1 side of the inner joint groove 16. In the present embodiment, two intermediate joint grooves 17 are provided between the inner joint groove 16 and the outer joint groove 18. The intermediate joint groove 17 includes a first intermediate joint groove 17A on the tire equator C side and a second intermediate joint groove 17B on the first tread end Te1 side. It is desirable that each intermediate joint groove 17 is inclined in the direction opposite to that of the inclined groove 10, for example.

It is desirable that the first intermediate joint groove 17A and the second intermediate joint groove 17B are located on the tire equator C side, for example, with respect to the center position of the first tread portion 2A in the tire axial direction. In the present embodiment, it is desirable that the distance L3 from the outer end in the tire axial direction to the tire equator C of the first intermediate joint groove 17A is, for example, 0.14 to 0.18 times the tread width TW. In the second intermediate joint groove 17B, for example, it is desirable that the distance L4 from the outer end in the tire axial direction to the first tread end Te1 is 0.20 to 0.30 times the tread width TW. A relatively large contact pressure acts on the first intermediate joint groove 17A and the second intermediate joint groove 17B of the present embodiment when traveling on snow, so that a hard snow column can be formed.

The intermediate joint groove 17 is formed so that the angle θ4 with respect to the tire circumferential direction is smaller than that of the inner joint groove 16. When the intermediate joint groove 17 is bent, the angle θ4 is an angle of a virtual straight line connecting both ends of the groove center line with respect to the tire circumferential direction.

Since a large contact pressure acts on the inner joint groove 16 arranged on the equator C side of the tire most when traveling straight on snow, it contributes greatly to traction on snow. Therefore, by relatively increasing the angle of the inner joint groove 16 with respect to the tire circumferential direction, the inner joint groove 16 can form a hard snow column together with the inclined groove 10, and thus can further enhance the traction on snow.

On the other hand, since the intermediate joint groove 17 is provided on the first tread end Te1 side of the inner joint groove 16, a larger contact pressure than the inner joint groove 16 acts on the intermediate joint groove 17 when the tire is turning. To do. In the present invention, paying attention to such a difference in contact pressure, the angle of the intermediate joint groove 17 with respect to the tire circumferential direction is set small. As a result, while obtaining the snow column shearing force in the intermediate joint groove 17, the lateral rigidity of the blocks divided on both sides of the intermediate joint groove 17 can be increased, and the steering stability on a dry road surface can be maintained.

In order to further exert the above-mentioned effect, the angle θ4 is preferably 45 ° or more, more preferably 50 ° or more, preferably 60 ° or less, and more preferably 55 ° or less.

FIG. 3 shows an enlarged view of the outline of the first intermediate joint groove 17A as a diagram for explaining the intermediate joint groove 17. As shown in FIG. 3, it is desirable that the intermediate joint groove 17 of the present embodiment has, for example, at least one bent portion 20. In a more preferred embodiment, the bent portion 20 includes two that are convex in opposite directions to each other. Such an intermediate joint groove 17 is useful for forming a hard snow column, and thus the performance on snow is enhanced.

The intermediate joint groove 17 has, for example, a pair of main inclined portions 21 and an auxiliary inclined portion 22 between them. The main inclined portion 21 extends from the inclined groove 10 at an angle θ5 of 45 to 55 ° with respect to the tire circumferential direction, for example.

The sub-tilted portion 22 has, for example, a length smaller than that of the main inclined portion 21. The sub-inclined portion 22 is inclined in the opposite direction to the main inclined portion 21, for example. The angle θ6 of the sub-inclined portion 22 with respect to the tire circumferential direction is preferably, for example, 65 to 80 °.

As shown in FIG. 2, the outer joint groove 18 is located, for example, on the first tread end Te1 side of the center position of the first tread portion 2A in the tire axial direction. For the outer joint groove 18, for example, it is desirable that the distance L5 from the outer end in the tire axial direction to the first tread end Te1 is 0.10 to 0.20 times the tread width TW.

It is desirable that the outer joint groove 18 is inclined in the direction opposite to that of the inclined groove 10, for example. In other words, it is desirable that the outer joint groove 18 is inclined in the same direction as the intermediate joint groove 17 and extends linearly. It is desirable that the outer joint groove 18 has a larger angle θ7 with respect to the tire circumferential direction than the intermediate joint groove 17, for example. More specifically, the angle θ7 of the outer joint groove 18 is at least larger than the angle θ5 (shown in FIG. 3) of the main inclined portion 21 of the intermediate joint groove 17. In a preferred embodiment, the angle θ7 of the outer joint groove 18 is larger than the angle θ4 of the virtual straight line connecting both ends of the groove center line of the intermediate joint groove 17. As a result, the block divided by the outer joint groove 18 is easily deformed appropriately in the tire circumferential direction. Therefore, when traveling on snow, the snow in the inclined groove 10 is further compacted, and excellent on-snow performance can be obtained. In particular, in the present embodiment, a larger effect can be expected in combination with the fact that the groove width of the inclined groove 10 gradually increases toward the first tread end Te1 side.

In a more desirable embodiment, the outer joint groove 18 has a smaller angle with respect to the tire circumferential direction than the inner joint groove 16 in order to exert the above effect while maintaining steering stability on a dry road surface. The angle θ7 of the outer joint groove 18 is preferably, for example, 60 to 70 °.

It is desirable that each of the above-mentioned joint grooves 16 to 18 has, for example, a groove width W2 that is 0.20 to 0.30 times the maximum groove width W1 of the inclined groove 10. Each of these joint grooves 16 to 18 can improve steering stability on a dry road surface and performance on snow in a well-balanced manner.

FIG. 4 shows a cross-sectional view taken along the line AA of the outer joint groove 18 as a diagram showing the cross-sectional shape of the joint groove 15. As shown in FIG. 4, it is desirable that the joint groove 15 has a maximum depth d2 that is 0.55 to 0.70 times the depth d1 of the inclined groove 10, for example.

In a desirable embodiment, it is desirable that the joint groove 15 has a raised bottom surface at both end portions 15a in the tire axial direction. It is desirable that the depth d3 of the end portion 15a is, for example, 0.65 to 0.80 times the maximum depth d2 of the joint groove 15. Such a joint groove 15 can further improve steering stability on a dry road surface.

A more detailed configuration of each groove will be described. FIG. 5 shows an enlarged view of the contours of the inclined groove 10, the central lateral groove 12, and the joint groove 15. As shown in FIG. 5, the intersection of the groove center line of the inclined groove 10 and the extension line of the groove center line of the outer joint groove 18 connected to the first-come-first-served side in the rotation direction R of the inclined groove 10 is the first intersection 26. It is said that. In order to improve steering stability on dry road surface and performance on snow in a well-balanced manner, the first distance L6 in the tire axial direction between the first tread end Te1 and the first intersection 26 is set to, for example, 0. It is desirable that it is 24 to 0.30 times.

The intersection of the groove center line of the inclined groove 10 and the extension line of the groove center line of the first intermediate joint groove 17A connected to the first-come-first-served side of the inclined groove 10 in the rotation direction R is defined as the second intersection 27. The second distance L7 in the tire axial direction between the first intersection 26 and the second intersection 27 is preferably, for example, 0.10 to 0.17 times the tread width TW.

The intersection of the extension line of the groove center line of the first central lateral groove 12A and the groove center line of the second inclined groove 10B is defined as the third intersection point 28. The third distance L8 in the tire axial direction between the second intersection 27 and the third intersection 28 is preferably, for example, 0.12 to 0.19 times the tread width TW.

The first straight line 31 extending from the intersection 10e between the first tread end Te1 and the groove center line of the inclined groove 10 to the first intersection 26 is inclined at an angle θ8 of, for example, 5 to 25 ° with respect to the tire axial direction. Is desirable. As a result, the inclined groove 10 can form a long snow column in the tire axial direction, especially in the vicinity of the first tread end Te1, and thus a large snow traction can be obtained.

It is desirable that the second straight line 32 extending from the second intersection 27 to the third intersection 28 is inclined at an angle θ9 of 32 to 52 ° with respect to the tire axial direction, for example.

The intersection of the groove center line of the inclined groove 10 and the extension line of the groove center line of the central lateral groove 12 which is connected to the tire equator C side of the inclined groove 10 is defined as the fourth intersection 29. It is desirable that the third straight line 33 extending from the second intersection 27 to the fourth intersection 29 is inclined at an angle θ10 of 51 to 71 ° with respect to the tire axial direction, for example.

In a more desirable embodiment, it is desirable that the central lateral groove 12 extends smoothly through the inclined groove 10 so as to be smoothly continuous with the inner joint groove 16. Such a central lateral groove 12 can form a long snow column in the tire axial direction together with the inner joint groove 16 when traveling on snow, which is useful for enhancing traction on snow.

FIG. 6 shows an enlarged view of the inclined land portion 13. As shown in FIG. 6, the inclined land portion 13 is divided into, for example, a crown block 35, a plurality of middle blocks 36, and a shoulder block 37.

The crown block 35 includes, for example, a region divided by the inner joint groove 16 and the inclined grooves 10 on both sides, and a region divided between the first central lateral groove 12A and the second central lateral groove 12B. The crown block 35 of the present embodiment has, for example, a tread surface surrounded by a first edge 35a, a second edge 35b, and a third edge 35c. The first edge 35a has, for example, a rotation direction. It is convex on the first-come-first-served side of R. The second end edge 35b is arranged on the rear arrival side in the rotation direction R with respect to the first end edge 35a, for example, and is recessed on the first arrival side. The third edge 35c connects the first edge 35a and the second edge 35b. As a result, the crown block 35 has a substantially U-shaped tread surface.

It is desirable that the crown block 35 is provided with, for example, at least one crown lug sipe 38. The crown lug sipe 38 has, for example, one end communicating with one of the grooves and the other end interrupted within the block. Such a crown lug sipe 38 can provide frictional force on, for example, a compacted snow-packed road surface while maintaining the rigidity of the crown block 35. In addition, in this specification, a sipe means a notch having a width of less than 1.5 mm.

The middle block 36 includes, for example, a first middle block 36A, a second middle block 36B, and a third middle block 36C. The first middle block 36A is divided between, for example, the inner joint groove 16 and the first intermediate joint groove 17A. The second middle block 36B is divided between, for example, the first intermediate joint groove 17A and the second intermediate joint groove 17B. The third middle block 36C is divided between, for example, the second intermediate joint groove 17B and the outer joint groove 18.

It is desirable that each middle block 36 be provided with, for example, a middle sipe 39 that completely crosses the block.

The shoulder block 37 is divided between, for example, the outer joint groove 18 and the first tread end Te1. The shoulder block 37 is provided with, for example, an outer lug groove 40 and a plurality of shoulder sipes 41.

The outer lug groove 40 extends from one of the adjacent inclined grooves 10 and is interrupted in the inclined land portion 13, for example. Such an outer lug groove 40 can improve the performance on snow while maintaining the rigidity of the shoulder block 37.

The outer lug groove 40 is inclined in the same direction as the outer joint groove 18 and extends linearly, for example. The outer lug groove 40 of the present embodiment extends along, for example, the outer joint groove 18. Such an outer lug groove 40 helps to make the rigidity distribution of the shoulder block 37 uniform and maintain steering stability on a dry road surface.

It is desirable that the outer lug groove 40 overlaps with the outer joint groove 18 in the tire axial direction, for example. This further enhances snow traction.

FIG. 7 shows a sectional view taken along line CC of the outer lug groove 40. As shown in FIG. 7, the outer lug groove 40 has, for example, a maximum depth d4 that is 0.50 to 0.65 times the depth d1 of the inclined groove 10.

It is desirable that the bottom surface of the outer lug groove 40 is raised, for example, at the end portion 40a connected to the inclined groove 10. It is desirable that the depth d5 of the end portion 40a is, for example, 0.65 to 0.75 times the maximum depth d4. Such an outer lug groove 40 can maintain the rigidity of the shoulder block 37 and thus improve the steering stability on a dry road surface.

As shown in FIG. 6, the shoulder sipe 41 includes, for example, a first shoulder sipe 41A and a second shoulder sipe 41B. The first shoulder sipe 41A is provided, for example, between the outer joint groove 18 and the outer lug groove 40 and completely crosses the block.

The second shoulder sipe 41B has, for example, one end connected to the inclined groove 10 and the other end extending to the first tread end Te1. Such a second shoulder sipe 41B can appropriately relax the rigidity of the shoulder block 37 and enhance the wandering performance.

It is desirable that the second shoulder sipe 41B includes, for example, an inclined sipe portion 43 and a lateral sipe portion 44. The inclined sipe portion 43 extends obliquely from, for example, the inclined groove 10. The inclined sipe portion 43 is inclined in the same direction as the outer lug groove 40, for example, and extends along the outer lug groove 40 in the present embodiment. It is desirable that the inclined sipe portion 43 extends in a zigzag shape, for example. The inclined sipe portion 43 can maintain the apparent rigidity of the shoulder block 37 by engaging the sipe walls with each other when the tire is running.

The lateral sipe portion 44 is connected to the outside of the inclined sipe portion 43 in the tire axial direction, and extends along the tire axial direction to the first tread end Te1. The lateral sipe portion 44 extends, for example, in a straight line. The second shoulder sipe 41B allows the lateral sipe portion 44 to undergo shear deformation in the tire axial direction of the shoulder block 37 even if the sipe walls come into contact with each other. Therefore, when traveling on snow, snow is likely to be discharged from the inclined groove 10.

In the present embodiment, it is desirable that the sipes provided in each block are formed in a zigzag shape except for the lateral sipe portion 44 of the second shoulder sipe 41B. Such sipes can maintain the apparent rigidity of each block, which in turn can improve steering stability on dry road surfaces.

In a preferred embodiment, the sipe preferably has, for example, a so-called Miura-folded sipe wall. In other words, in the sipe, the opening edge shape opened at the tread of the block has a zigzag-shaped portion, and the zigzag-shaped portion is a sipe while substantially maintaining the opening edge shape in the depth direction. Is displaced in the length direction of. Moreover, the displacement of the zigzag-shaped portion changes its direction at the corner portion. In such a sipe, the sipe walls can mesh with each other more strongly, and the rigidity of the block can be maintained.

As shown in FIG. 1, the land ratio Lr of the tread portion 2 of the present embodiment is preferably 60% or more, more preferably 65% or more, preferably 80% or less, and more preferably 75% or less. .. As a result, steering stability on dry roads and performance on ice and snow can be improved in a well-balanced manner. In the present specification, the “land ratio” is the ratio Sb / Sa of the actual total ground contact area Sb to the total area Sa of the virtual ground contact patch in which each groove and sipe are completely filled.

From the same viewpoint, the rubber hardness Ht of the tread rubber forming the tread portion 2 is preferably 45 ° or more, more preferably 55 ° or more, preferably 70 ° or less, and more preferably 65 ° or less. In the present specification, the "rubber hardness" is the hardness according to durometer type A in an environment of 23 ° C. in accordance with JIS-K6253.

8 and 9 show a development view of the tread portion 2 of the tire 1 according to another embodiment of the present invention. In FIGS. 8 and 9, the elements common to the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted here.

In the embodiment shown in FIG. 8, each joint groove 15 extends linearly. In such an embodiment, since each joint groove 15 exhibits excellent drainage property, for example, excellent performance can be exhibited on a road surface in which snow and water are mixed.

In the embodiment shown in FIG. 9, not only the intermediate joint groove 17, but also the inner joint groove 16 and the outer joint groove 18 have two bent portions that are convex in opposite directions to each other. Such an inner joint groove 16 and an outer joint groove 18 are useful for forming a hard snow column, and thus the performance on snow is enhanced.

Although the tire of one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and may be modified to various embodiments.

A size 205 / 55R16 pneumatic tire with the basic tread pattern of FIG. 1 was prototyped based on the specifications in Table 1. As a comparative example, as shown in FIG. 10, a tire having an inner joint groove formed at a smaller angle with respect to the tire circumferential direction than the intermediate joint groove was prototyped. The steering stability and snow performance of each test tire on dry roads were tested. The common specifications and test methods for each test tire are as follows.
Tread ground contact width: 160 mm
Groove depth of inclined groove: 8.6 mm
Land ratio: 70%
Rubber hardness of tread rubber Ht: 65
Rim: 16 x 6.5
Tire internal pressure: 200kPa
Test vehicle: Displacement 2000cc, front-wheel drive vehicle Test tire mounting position: All wheels

<Maneuvering stability on dry roads>
The driving stability of the test vehicle when traveling on a dry road surface circuit course was evaluated by the driver's sensuality. The result is a score of 100 in the comparative example, and the larger the value, the better the steering stability on the dry road surface.

<Performance on snow>
The driving performance of the test vehicle when traveling on a snowy road was evaluated by the driver's sensuality. The result is a score with a comparative example of 100, and the larger the value, the better the performance on snow.
The test results are shown in Table 1.

As a result of the test, it was confirmed that the pneumatic tire of the example exhibited excellent on-snow performance while maintaining steering stability on a dry road surface.

2 Tread part 10 Inclined groove 13 Inclined land part 15 Joint groove 16 Inner joint groove 17 Intermediate joint groove Te1 1st tread end

Claims (10)

A tire with a tread
The tread portion includes a plurality of inclined grooves extending diagonally from the first tread end on one side in the tire axial direction toward the tire equator side, and a plurality of inclined grooves partitioned between the inclined grooves adjacent to each other in the tire circumferential direction. A sloping land area is provided,
The inclined land portion is provided with a plurality of joint grooves communicating between the inclined grooves.
The joints include an inner joint groove most arranged on the equator side of the tire, at least one intermediate joint groove arranged adjacent to the first tread end side of the inner joint groove, and the first tread. Including an outer joint groove different from the intermediate joint groove arranged on the end side,
The intermediate connecting grooves, the angle is rather small with respect to the tire circumferential direction than the inner connecting grooves,
The outer joint groove is a tire having a larger angle with respect to the tire circumferential direction than the intermediate joint groove. The tire according to claim 1, wherein the inclined groove is curved so that the angle with respect to the tire axial direction gradually increases toward the equator side of the tire. The tire according to claim 1 or 2, wherein the intermediate joint groove has at least one bent portion. The tire according to claim 3, wherein the bent portion includes two tires that are convex in opposite directions. The tire according to any one of claims 1 to 4, wherein the outer joint groove has a smaller angle with respect to the tire circumferential direction than the inner joint groove. The tire according to any one of claims 1 to 5, wherein two intermediate joint grooves are provided between the inner joint groove and the outer joint groove. The tire according to any one of claims 1 to 6, wherein the intermediate joint groove and the outer joint groove are inclined in the direction opposite to the inclined groove. The invention according to any one of claims 1 to 7, wherein an outer lug groove extending from one of the adjacent inclined grooves and interrupted in the inclined land portion is provided between the outer joint groove and the first tread end. tire. The sloping groove breaks without crossing the tire equator,
The tire according to any one of claims 1 to 8, wherein a central lateral groove that branches from the inclined groove and extends in the tire axial direction and crosses the tire equator is provided. The tire according to claim 9, wherein the central lateral groove extends smoothly through the inclined groove so as to be smoothly continuous with the inner joint groove.

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