JP5957415B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which ice road performance, uneven wear resistance performance and drainage performance are improved in a well-balanced manner.

  In recent years, in winter pneumatic tires, opportunities to travel on wet roads as well as ice roads are increasing. Therefore, in such a pneumatic tire for winter, it is required to improve not only the icy road performance but also the drainage performance at a high level in a well-balanced manner.

  For example, in order to improve drainage performance, it has been proposed to increase the width of main grooves and lateral grooves in order to smoothly drain the water film between the land portion of the tread portion and the road surface. .

  However, in the pneumatic tire as described above, since the contact area of the land portion is small, there is a problem that the frictional force and the pattern rigidity are lowered, and the ice road performance and the uneven wear resistance performance are deteriorated. As a related technique, there is Patent Document 1 below.

JP 2010-149599 A

  The present invention has been devised in view of the actual situation as described above, and in the center land portion, provided with a center notch extending from the center main groove, and defining the shape of the center notch, The main purpose is to provide a pneumatic tire with improved icy road performance, uneven wear resistance and drainage performance in a well-balanced manner.

According to the first aspect of the present invention, the tread portion has a pair of center main grooves extending continuously in the tire circumferential direction on both sides in the tire axial direction of the tire equator, and a tire axial direction outer side of the center main groove on the tire A pair of shoulder main grooves extending continuously in the circumferential direction, a plurality of middle lateral grooves connecting between the center main groove and the shoulder main grooves, and a plurality of connecting between the shoulder main grooves and the grounding end By providing the shoulder lateral groove, one center land portion divided by the pair of center main grooves, the middle block divided by the center main groove, the shoulder main groove, and the middle lateral groove are arranged in the tire circumferential direction. A pair of middle block rows that are spaced apart and a shoulder block that is partitioned by the shoulder main groove, the ground contact end, and the shoulder lateral groove are spaced apart in the tire circumferential direction. A pneumatic tire comprising a shoulder block row of pairs, the center main groove includes a plurality of center long side portion inclined to one side with respect to the tire circumferential direction, the Center adjacent in the tire circumferential direction A plurality of center short side portions arranged between the side portions and having a length in the tire circumferential direction smaller than the center long side portion are alternately arranged, and the center land portion is arranged on the tire equator side from the center main groove. A center notch portion extending in the center land portion is provided, and the center notch portion has a maximum length in the tire axial direction of 10-15% of the maximum length in the tire axial direction of the center land portion, 10-15% of the tire circumferential direction of the length of the opening edge one pitch of the shoulder block row, and a depth of 55 to 65% of the groove depth of the center main groove, and, with the center long side portion the Center The shoulder main groove is provided so as to include an intersection with a side portion, and the shoulder main groove is connected between a plurality of shoulder long side portions inclined to one side with respect to the tire circumferential direction and a shoulder long side portion adjacent to the tire circumferential direction. And a zigzag shape in which a shoulder short side portion having a smaller length in the tire circumferential direction than the shoulder long side portion is alternately arranged, and the middle block extends from the shoulder main groove to the tire equator side. the middle can outer middle notch terminating in a block is provided, the outer middle notch is characterized Rukoto provided in the shoulder short side.

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the center notch has a polygonal shape having four or more sides in plan view.

In the invention according to claim 3, the middle block is provided with an inner middle notch extending from the center main groove outward in the tire axial direction and terminating in the middle block.
3. The pneumatic tire according to claim 1 , wherein the inner middle notch portion is provided at the center short side portion .

  According to a fourth aspect of the present invention, the land ratio, which is the ratio of the total surface area of the tread portion and the virtual surface area of the virtual tread surface obtained by filling all the grooves of the tread portion, is 68 to 72%. A pneumatic tire according to any one of claims 1 to 3.

According to a fifth aspect of the present invention, the middle outer block edge of the middle block extending in the tire axial direction outer side and in the tire circumferential direction has a middle outer short side inclined to the other side opposite to one side with respect to the tire circumferential direction. And a pair of middle outer long edges that are inclined from both ends of the middle outer short edge to the opposite side of the middle outer short edge and are longer in the tire circumferential direction than the middle outer short edge 5. The pneumatic tire according to claim 1, wherein the outer middle notch has a notched edge that smoothly extends the middle outer long edge.

In the invention according to claim 6, the shoulder block row includes a plurality of shoulder long edges extending with the tire equator side inclined toward one side with respect to the tire circumferential direction, and the shoulder long edges adjacent in the tire circumferential direction. A plurality of shoulder short edges that are smaller in length in the tire circumferential direction than the shoulder long edge, and the shoulder lateral groove has a groove bottom at a position shallower than the shoulder main groove, and the shoulder a pneumatic tire according to any one of claims 1 to 5 that are open at the short edges.

In the invention according to claim 7, the land portion edge extending in the tire circumferential direction of the center land portion is the center long edge portion extending along the center long side portion, and the center long edge portion adjacent in the tire circumferential direction. A middle inner block edge extending in the tire axial direction inside and in the tire circumferential direction of the middle block is inclined to the other side opposite to one side with respect to the tire circumferential direction. A middle inner short edge portion and a pair of middle inclining from both ends of the middle inner short edge portion to the opposite side of the middle inner short edge portion and having a longer length in the tire circumferential direction than the middle inner short edge portion An inner long edge portion, and the center short edge portion is provided with an overlapping portion that overlaps with the middle inner short edge portion in the tire circumferential direction, and an arrangement pitch of the center short edge portion and the middle inner short edge portion The arrangement pitch is the same That is a pneumatic tire according to any one of claims 1 to 6.

In the invention according to claim 8, the middle block is provided with an inner middle notch extending from the center main groove outward in the tire axial direction and terminating in the middle block, and the inner middle notch is The pneumatic tire according to claim 7, further comprising a notched edge that smoothly extends the middle inner long edge portion .

  In the pneumatic tire of the present invention, the tread portion has a pair of center main grooves extending continuously in the tire circumferential direction on both sides in the tire axial direction of the tire equator, and the tire axial direction outer side of the center main groove is continuous in the tire circumferential direction. A pair of extending shoulder main grooves, a plurality of middle horizontal grooves that connect between the center main groove and the shoulder main grooves, and a plurality of shoulder horizontal grooves that connect between the shoulder main groove and the grounding end are provided. Thus, a pair of center land portions divided by a pair of center main grooves, middle blocks divided by a center main groove, a shoulder main groove, and a middle lateral groove are provided in the tread portion in the tire circumferential direction. And a pair of shoulder block rows in which a shoulder block divided by a shoulder main groove, a ground contact end, and a shoulder lateral groove is spaced apart in the tire circumferential direction.

  The center land portion is provided with a center cutout portion extending from the center main groove to the tire equator side and terminating in the center land portion. The center notch portion has a maximum length in the tire axial direction of 10 to 15% of a maximum length in the tire axial direction of the center land portion, and a length in the tire circumferential direction of the opening edge is 10 to 10% of one pitch of the shoulder block row. 15% and the depth is 55 to 65% of the groove depth of the center main groove. Such a center notch has edge components in the tire axial direction and the tire circumferential direction. Further, the center cutout portion maintains the rigidity of the center land portion high. Further, the center notch smoothly drains the water film between the center land and the road surface. Therefore, in the pneumatic tire of the present invention, ice road performance, uneven wear resistance performance and drainage performance are improved in a well-balanced manner.

It is an expanded view of the tread part which shows one Embodiment of this invention. It is an enlarged view of the left half of the tread part of FIG. It is sectional drawing of the XX part of FIG. FIG. 3 is an enlarged view of the vicinity of the middle block in the tread portion of FIG. 2. It is an expanded view of the tread part of other embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the pneumatic tire of this embodiment (hereinafter simply referred to as “tire”) can be suitably used as, for example, a winter tire, and the tread portion 2 includes a tire equator C. A pair of center main grooves 3A extending continuously in the tire circumferential direction on both sides in the tire axial direction and a pair of shoulder main grooves 3B extending continuously in the tire circumferential direction on the outer side in the tire axial direction of the center main groove 3A are provided. It is done. In the present embodiment, the tread portion 2 has a plurality of middle lateral grooves 4A that connect between the center main groove 3A and the shoulder main groove 3B, and a plurality of connections that connect between the shoulder main groove 3B and the grounding end Te. Shoulder lateral groove 4B is provided.

  As a result, the tread portion 2 of the present embodiment includes a center land portion 5 divided by a pair of center main grooves 3A, 3A, a plurality of portions divided by the center main groove 3A, the shoulder main groove 3B, and the middle lateral groove 4A. The middle block 6 is a pair of middle block rows 6R spaced apart in the tire circumferential direction, and a plurality of shoulder blocks 7 divided by the shoulder main groove 3B, the ground contact Te and the shoulder lateral groove 4B are arranged in the tire circumferential direction. A pair of spaced shoulder block rows 7R are arranged.

  The tread pattern of the present embodiment is formed in a substantially point-symmetric pattern except for a variable pitch with an arbitrary point on the tire equator C as the center.

  The “grounding end” Te is applied to a flat tire with a camber angle of 0 ° by applying a normal load to an unloaded normal tire that is assembled to a normal rim (not shown) and filled with a normal internal pressure. Is defined as the contact position on the outermost side in the tire axial direction. The distance in the tire axial direction between the ground contact Te and Te is determined as the tread ground contact width TW. When there is no notice in particular, the dimension of each part of a tire is the value measured in the said normal state.

  The “regular rim” is a rim defined for each tire in the standard system including the standard on which the tire is based. “Standard Rim” for JATMA, “Design Rim” for TRA For ETRTO, "Measuring Rim". In addition, the “regular internal pressure” is an air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum value described in TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES is "INFLATION PRESSURE" for ETRTO, but 180 kPa for tires for passenger cars.

  The “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. “Maximum load capacity” for JATMA, “Table for TRA” The maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is “LOAD CAPACITY” if it is ETRTO, but if the tire is for a passenger car, the load is equivalent to 88% of the above load.

  The center main groove 3A of the present embodiment includes a plurality of center long side portions 8A inclined to one side with respect to the tire circumferential direction (inclined to the left in FIG. 1), and a center long side portion adjacent to the tire circumferential direction. It is formed in a zigzag shape in which the center short side portions 8B, which are connected between 8A and 8A and are smaller in the tire circumferential direction than the center long side portion 8A, are alternately arranged. Since the center main groove 3A includes an edge component in the tire axial direction, the driving force and the braking force are increased. Therefore, ice road performance is improved.

  The angle of the center main groove 3A is obtained as the angle of the groove center line 10. The center long side portion 8A of the present embodiment has a groove center line 10a that is inclined to one side with respect to the tire circumferential direction (inclined to the left in FIG. 1). Moreover, the center short side part 8B of this embodiment has the groove center line 10b which inclines on the other side with respect to a tire circumferential direction (in FIG. 1, it inclines rightward).

  FIG. 2 shows an enlarged view of the left half of the tread portion 2 of FIG. As shown in FIG. 2, the groove center line 10 of the center main groove 3A has an innermost point a1 in the tire axial direction of the inner groove edge 10x on the inner side in the tire axial direction of the center main groove 3A and the center main groove 3A. An intermediate point s1 of the outer groove edge 10y on the outer side in the tire axial direction with the innermost point a2 in the tire axial direction, and an outermost point a3 of the inner groove edge 10x in the tire axial direction and the outer groove edge 10y in the tire axial direction. It is formed by a straight line that alternately connects intermediate points s2 with the outermost point a4 (note that the groove center line 14 of the shoulder main groove 3B is defined in the same manner). In FIG. 2, an intersection position 8e between the center long side portion 8A and the center short side portion 8B is indicated by a virtual line. In the present specification, the inner groove edge 10x and the outer groove edge 10y of the center main groove 3A are defined by the boundary between the center main groove 3A and the center land portion 5, and have a depth smaller than the groove depth of the center main groove 3A. For example, an opening edge on the center main groove 3A side such as a notch or a lug groove is included.

  As shown in FIG. 1, when the angle α1 of the center long side portion 8A with respect to the tire circumferential direction is small, the edge component in the tire axial direction may be reduced. When the angle α1 of the center long side portion 8A is large, the drainage resistance of the center main groove 3A is increased, and the drainage performance may be deteriorated. For this reason, the angle α1 of the center long side portion 8A is preferably 5 ° or more, more preferably 7 ° or more, preferably 20 ° or less, more preferably 18 ° or less.

  Although not particularly limited, the angle α2 of the center short side portion 8B with respect to the tire circumferential direction is preferably 30 ° or more, more preferably 35 ° or more, preferably 60 ° or less, more preferably 55 ° or less. It is. When the angle α2 of the center short side 8B is large, the drainage performance may be deteriorated. When the angle α2 of the center short side portion 8B is small, there is a possibility that the ice road performance is deteriorated.

  The shoulder main groove 3B of the present embodiment also has a plurality of shoulder long side portions 11A inclined to one side with respect to the tire circumferential direction (inclined to the left in FIG. 1), and a shoulder long side portion adjacent to the tire circumferential direction. 11A, 11A is formed in a zigzag shape in which shoulder short side portions 11B having a smaller length in the tire circumferential direction than the shoulder long side portion 11A are alternately arranged. Similar to the center main groove 3A, such a shoulder main groove 3B also includes an edge component in the tire axial direction, and improves ice road performance.

  From the viewpoint of improving icy road performance and drainage performance in a well-balanced manner, the angle α3 of the shoulder long side portion 11A with respect to the tire circumferential direction is preferably 5 ° or more, more preferably 7 ° or more, and preferably 20 ° or less. More preferably, it is 18 ° or less. The angle α4 of the shoulder short side portion 11B with respect to the tire circumferential direction is preferably 30 ° or more, more preferably 35 ° or more, preferably 60 ° or less, more preferably 55 ° or less.

  The groove width of each main groove 3A, 3B (the groove width measured in the direction perpendicular to the groove center line, hereinafter the same applies to other grooves) W1, W2 and groove depths D1, D2 (in FIG. 3) (Shown) can be variously determined in accordance with common practice. However, when these groove widths or groove depths are reduced, drainage performance may be deteriorated. On the contrary, when these groove widths or groove depths are increased, the rigidity of the land portion 5 and each of the blocks 6 and 7 is decreased, and the uneven wear resistance performance may be deteriorated. For this reason, the groove widths W1 and W2 of the main grooves 3A and 3B are preferably 2 to 6% of the tread ground contact width TW, for example. As for groove depth D1, D2 of each main groove 3A, 3B, 10-15 mm is desirable, for example.

  The tire axial distance L1 between the center main groove 3A and the tire equator C is 5 to 13% of the tread ground contact width TW in order to ensure a good balance of the rigidity in the tire axial direction of the land portion 5 and the blocks 6 and 7. Is desirable. The tire axial distance L2 between the shoulder main groove 3B and the tire equator C is preferably 24 to 32% of the tread contact width TW. Note that the positions of the main grooves 3A and 3B are as follows. When the main grooves 3A and 3B are zigzag non-linear as in the present embodiment, the center lines G1 and G2 having the amplitude of the groove center lines 10 and 14 are Used.

  The middle lateral groove 4A includes a pair of middle outer portions 12a that are linearly inclined on both sides in the longitudinal direction at a certain angle with respect to the tire axial direction (inclined to the left in FIG. 1), the pair of middle outer portions 12a, A crank shape is formed including the middle inner portion 12b that connects between the two outer portions 12a and is inclined at a larger angle than the middle outer portion 12a. Such a middle lateral groove 4A has a large edge component in the tire circumferential direction, and improves ice road performance.

  When the angle α5 of the middle outer portion 12a with respect to the tire axial direction is large, the edge component of the middle block 6 in the tire axial direction becomes small, and the driving and braking force may be reduced. When the angle α5 of the middle outer portion 12a is small, the edge component in the tire circumferential direction may not be effectively increased. For this reason, the angle α5 of the middle outer portion 12a is preferably 3 ° or more, more preferably 4 ° or more, preferably 10 ° or less, and more preferably 9 ° or less.

  When the angle α6 of the middle inner portion 12b with respect to the tire axial direction is large, the rigidity of the middle block 6 in the tire axial direction is reduced, and the uneven wear resistance may be deteriorated. When the angle α6 is small, the edge component in the tire circumferential direction may not be effectively increased. For this reason, the angle α6 of the middle inner portion 12b is preferably 45 ° or more, more preferably 55 ° or more, preferably 75 ° or less, and more preferably 70 ° or less.

  When the groove width W3 and the groove depth D3 (shown in FIG. 3) of the middle lateral groove 4A are large, the rigidity of the middle block 6 may be reduced. When the groove width W3 and the groove depth D3 of the middle lateral groove 4A are small, the drainage performance may be deteriorated. For this reason, the groove width W3 of the middle lateral groove 4A is preferably 1.5 mm or more, more preferably 2.0 mm or more, and preferably 3.5 mm or less, more preferably 3.0 mm or less. The groove depth D3 of the middle lateral groove 4A is preferably 6.5 mm or more, more preferably 7.0 mm or more, preferably 10.0 mm or less, more preferably 9.5 mm or less. The middle lateral groove 4A of the present embodiment has a uniform width.

  In the present embodiment, the shoulder lateral groove 4B has an inclined portion 13a inclined from the shoulder main groove 3B toward the grounding end Te toward one side (inclined upward in FIG. 1), the inclined portion 13a and the grounding end Te. And an axial portion 13b extending along the tire axial direction. The inclined part 13a and the axial direction part 13b of this embodiment extend linearly. Thereby, the drainage resistance of the shoulder lateral groove 4B becomes small. Moreover, the rigidity of the shoulder block 7 is ensured and the turning performance is improved.

  Although not particularly limited, the angle α7 of the inclined portion 13a with respect to the tire axial direction is preferably 10 ° or more, more preferably 12 ° or more, preferably 20 ° or less, more preferably 18 ° or less. .

  The groove width W4 of the inclined portion 13a is preferably 6% or more, more preferably 8% or more, preferably 16% or less, more preferably 14% or less, of one pitch P1 of the shoulder block row 7R. When the groove width W4 of the inclined portion 13a is large, the rigidity of the shoulder block 7 may be reduced. When the groove width W4 of the inclined portion 13a is small, the drainage performance may be deteriorated.

  In this embodiment, the groove width W5 of the axial part 13b is formed larger than the groove width W4 of the inclined part 13a. Thereby, the water from the inclined part 13a is smoothly discharged to the grounding end Te side. In order to ensure the rigidity of the shoulder block 7 while exhibiting the above-described action, the groove width W5 of the axial portion 13b is preferably 1.2 times or more, more preferably 1.3 times the groove width W4 of the inclined portion 13a. It is more than twice, preferably less than 2.4 times, more preferably less than 2.3 times.

  As shown in FIG. 3, the groove depth D4 of the inclined portion 13a is preferably 5.0 mm or more, more preferably 5.5 mm or more, preferably 8.0 mm or less, more preferably 7.5 mm or less. is there. In the present embodiment, the groove depth D5 in the axial direction portion is made larger than the groove depth D4 in the inclined portion, and the drainage in the shoulder lateral groove 4B is smoothly discharged to the ground contact Te. For this reason, the groove depth D5 of the axial direction portion 13b is preferably 1.2 times or more, more preferably 1.3 times or more, preferably 1.8 times or less, preferably the groove depth D4 of the inclined portion 13a. More preferably, it is 1.7 times or less.

  As shown in FIG. 2, the center land portion 5 is provided with a center notch portion 17 extending from the center main groove 3 </ b> A to the tire equator C side and terminating in the center land portion 5. Since such a center notch 17 has an edge component, it improves ice road performance. The center cutout portions 17 of the present embodiment are arranged so as to be alternately displaced in both sides of the center land portion 5 in the tire axial direction and in the tire circumferential direction. The depth D6 (shown in FIG. 3) of the center notch portion 17 is smaller than the groove depth D1 (shown in FIG. 3) of the center main groove 3A. Thereby, the rigidity of the tire land direction of the center land part 5 is ensured highly.

  The center notch portion 17 has a maximum length L3 in the tire axial direction of 10 to 15% of a maximum length Wc (shown in FIG. 1) of the center land portion 5 in the tire axial direction, and the length of the opening edge in the tire circumferential direction. L4 is 10 to 15% of one pitch P1 (shown in FIG. 1) of the shoulder block row 7R, and the depth D6 (shown in FIG. 3) is 55 to 65% of the groove depth D1 of the center main groove 3A. .

  When the maximum length L3 of the center notch portion 17 in the tire axial direction is less than 10% of the maximum length Wc of the center land portion 5, the drainage performance cannot be improved. Further, a large edge component of the center notch portion 17 cannot be ensured, and ice road performance cannot be improved. When the maximum length L3 of the center notch portion 17 in the tire axial direction exceeds 15% of the maximum length Wc of the center land portion 5, the rigidity of the center land portion 5 is deteriorated. For this reason, the maximum length L3 of the center notch portion 17 is preferably 11% or more and preferably 14% or less of the maximum length Wc of the center land portion 5.

  Similarly, when the length L4 in the tire circumferential direction of the opening edge of the center notch portion 17 is less than 10% of one pitch P1 of the shoulder block row 7R, the drainage performance cannot be improved. When the length L4 in the tire circumferential direction of the opening edge exceeds 15% of the shoulder block row 7R, the surface area of the tread surface of the center land portion 5 becomes small, and the rigidity of the center land portion 5 deteriorates. For this reason, the length L4 in the tire circumferential direction of the opening edge is preferably 11% or more, and preferably 14% or less of one pitch P1 of the shoulder block row 7R.

  When the depth D6 of the center notch portion 17 exceeds 65% of the groove depth D1 of the center main groove 3A, the rigidity of the center land portion 5 is lowered. When the depth D6 of the center cutout portion 17 is less than 55% of the groove depth D1 of the center main groove 3A, the drainage performance cannot be sufficiently improved. For this reason, the depth D6 of the center notch portion 17 is preferably 57% or more and preferably 63% or less of the groove depth D1 of the center main groove 3A.

  Thus, by defining the maximum length L3 in the tire axial direction of the center notch portion 17, the length L4 in the tire circumferential direction of the opening edge, and the depth D6, ice road performance, uneven wear resistance performance and Drainage performance is improved in a well-balanced manner.

  The shape of the center notch 17 in plan view is not particularly limited. However, when the center notch portion 17 has a triangular shape, ice scraped by the edge of the center notch portion 17 may enter the center notch portion 17 and the ice road performance may be degraded. For this reason, the shape of the center notch 17 is preferably a polygon having four or more sides. If the center notch 17 has a polygonal shape with 6 or more sides, drainage resistance may increase. In addition, such a notch is difficult to manufacture, and productivity may be deteriorated. For this reason, the center cutout portion 17 is preferably a polygonal shape having sides of 5 or less. The “side” is a part of the inner groove edge 10x of the center main groove 3A (that is, the opening edge of the center notch portion 17) and the center notch portion 17 extending in the center land portion 5 in plan view. An edge.

  In order to enhance the edge effect while suppressing the entrance of ice into the center cutout portion 17, the inner angle θ () of each side excluding the inner groove edge 10x forming the center cutout portion 17 in plan view. 4) is preferably 60 ° or more, more preferably 65 ° or more, preferably 120 ° or less, more preferably 115 ° or less.

  The center cutout portion 17 is provided including an intersection 8k between the center long side portion 8A and the center short side portion 8B. The intersection 8k in the present embodiment is a bent corner on the protruding corner side that is convex and bent on the side opposite to the groove center line 10 of the center main groove 3A. Such a center cutout portion 17 ensures a high rigidity at the intersection 8k where the ground contact pressure is highest in the center land portion 5, and thus improves uneven wear resistance.

  FIG. 4 shows a further enlarged view of the vicinity of the center main groove 3A in FIG. As shown in FIG. 4, the center land portion 5 has a pair of land portion edges 15 extending on both sides in the tire axial direction and in the tire circumferential direction (FIG. 4 shows a land portion edge 15 on the left side of the center land portion 5. Have). The land portion edge 15 includes a center long edge portion 15A extending along the center long side portion 8A and a center short edge portion 15B disposed between the center long edge portions 15A and 15A adjacent in the tire circumferential direction. The center long edge portion 15A of the present embodiment is a land portion edge that inclines to one side (inclined to the left in FIG. 1). The center short edge portion 15B is a land portion edge that is inclined to the other side opposite to the center long edge portion 15A (inclined upward in FIG. 1).

  The center cutout portion 17 has a cutout edge 17a that is smoothly connected to the center short edge portion 15B. Such a notch edge 17a further reduces the contact pressure at the intersection 8k. Further, the water in the center notch 17 is smoothly guided to the center main groove 3A. In the present embodiment, the center short edge portion 15B and the cutout edge 17a are formed in a straight line.

  The middle block 6 has a middle inner block edge 19 extending in the tire axial direction and in the tire circumferential direction, and a middle outer block edge 20 extending in the tire axial direction and in the tire circumferential direction.

  The middle inner block edge 19 has a middle inner short edge portion 19A inclined to one side with respect to the tire circumferential direction (inclined to the right in FIG. 4), and a middle inner short edge from both ends of the middle inner short edge portion 19A. It includes a pair of middle inner long edges 19B, 19B that are inclined to the opposite side of the portion 19A (inclined to the left in FIG. 4) and have a length in the tire circumferential direction larger than the middle inner short edge 19A. The middle outer block edge 20 has a middle outer short edge portion 20A inclined to one side with respect to the tire circumferential direction (inclined to the right in FIG. 4), and a middle outer short edge from both ends of the middle outer short edge portion 20A. It includes a pair of middle outer long edge portions 20B and 20B that are inclined to the opposite side of the portion 20A (inclined to the left in FIG. 4) and have a longer tire circumferential length than the middle outer short edge portion 20A. In the present embodiment, the arrangement pitch of the center short edge portion 15B and the arrangement pitch of the middle inner short edge portion 19A are the same.

  The center short edge portion 15B is provided with an overlapping portion 21 overlapping the middle inner short edge portion 19A in the tire circumferential direction. Such an overlapping portion 21 ensures a small drainage resistance of the center main groove 3A. Moreover, the rigidity of the center land part 5 and the middle block 6 between the overlapping parts 21 and 21 adjacent to a tire peripheral direction is ensured highly. The length Lk of the overlapping portion 21 in the tire circumferential direction is preferably 6.5% or more, more preferably 7.0% or more, and preferably 10.5% of one pitch P2 of the middle block row 6R. Hereinafter, it is more preferably 10.0% or less.

  The middle block 6 extends from the center main groove 3A outward in the tire axial direction and ends in the middle block 6, and extends from the shoulder main groove 3B to the tire equator C side and ends in the middle block 6. An outer middle notch 24 is provided. The depth D7 (shown in FIG. 3) of the inner middle notch 23 is smaller than the groove depth D1 (shown in FIG. 3) of the center main groove 3A. The depth D8 (shown in FIG. 3) of the outer middle notch 24 is smaller than the groove depth D2 (shown in FIG. 3) of the shoulder main groove 3B. Since the notches 23 and 24 smoothly drain the water film between the middle block 6 and the road surface to the center main groove 3A or the shoulder main groove 3B, the drainage performance is improved. Since each notch part 23 and 24 has an edge component, it improves ice road performance. Further, the notches 23 and 24 ensure a high rigidity of the middle block 6.

  The inner middle notch portion 23 is provided in the center short side portion 8B, and the outer middle notch portion 24 is provided in the shoulder short side portion 11B. Thus, since each notch part 23 and 24 is provided in the center short side part 8B and shoulder short side part 11B with large drainage resistance, the drainage resistance of the center main groove 3A and the shoulder main groove 3B is reduced, and drainage performance Is further improved.

  In the present embodiment, the opening edge of the inner middle notch 23 is formed over the entire length of the middle inner short edge 19A. Similarly, the opening edge of the outer middle notch portion 24 of the present embodiment is formed over the entire length of the middle outer short edge portion 20A. Thereby, the water in the notches 23 and 24 can be smoothly discharged to the center long side 8A or the shoulder long side 11A. Accordingly, the drainage performance is further improved.

  The inner middle notch portion 23 of the present embodiment has a notch edge 23a that smoothly extends the middle inner long edge portion 19B. Such a notch edge 23a can smoothly guide the water in the inner middle notch 23 to the center main groove 3A while increasing the rigidity of the intersection of the middle inner long edge 19B and the middle inner short edge 19A. it can. The outer middle notch portion 24 of the present embodiment has a notch edge 24a that smoothly extends the middle outer long edge portion 20B. The notch edge 24a can smoothly guide the water in the outer middle notch 24 to the shoulder main groove 3B while increasing the rigidity of the intersection of the middle outer long edge 20B and the middle outer short edge 20A. In the present embodiment, the middle inner long edge portion 19B and the cutout edge 23a are formed in a straight line shape. Further, the middle outer long edge portion 20B and the cutout edge 24a are formed in a straight line shape.

  When the maximum length L5 of the inner middle notch 23 in the tire axial direction is large, the rigidity of the middle block 6 is reduced, and the uneven wear resistance may be deteriorated. When the maximum length L5 of the inner middle notch 23 in the tire axial direction is small, the edge component of the inner middle notch 23 becomes smaller. For this reason, the maximum length L5 in the tire axial direction of the inner middle notch 23 is preferably 10% or more, more preferably 11% or more of the maximum length Wm of the middle block 6 in the tire axial direction, preferably It is 15% or less, more preferably 14% or less. From the same viewpoint, the maximum length L7 of the outer middle notch 24 in the tire axial direction is preferably 10% or more, more preferably 11% or more of the maximum length Wm of the middle block 6 in the tire axial direction. Preferably it is 15% or less, More preferably, it is 14% or less.

  When the length L6 in the tire circumferential direction of the opening edge of the inner middle notch portion 23 is large, the rigidity of the middle block 6 is reduced, and the uneven wear resistance may be deteriorated. When the length L6 in the tire circumferential direction of the opening edge of the inner middle notch 23 is small, the drainage performance may be deteriorated. For this reason, the length L6 in the tire circumferential direction of the opening edge is preferably 10% or more, more preferably 11% or more, and preferably 15% or less of one pitch P1 (shown in FIG. 1) of the shoulder block row 7R. More preferably, it is 14% or less. Similarly, the length L8 in the tire circumferential direction of the opening edge of the outer middle notch 24 is preferably 10% or more, more preferably 11% or more, and preferably 15% of one pitch P1 of the shoulder block row 7R. Below, more preferably 14% or less.

  As shown in FIG. 3, the depth D7 of the inner middle notch 23 is preferably 55% or more, more preferably 57% or more, preferably 65% or less of the groove depth D1 of the center main groove 3A. More preferably, it is 63% or less. That is, when the depth D7 of the inner middle notch 23 is large, the rigidity of the middle block 6 is reduced, and the uneven wear resistance may be deteriorated. When the depth D7 of the inner middle notch 23 is small, the drainage performance may not be improved. From the same viewpoint, the depth D8 of the outer middle notch 24 is preferably 55% or more, more preferably 57% or more, preferably 65% or less of the groove depth D2 of the shoulder main groove 3B. Is 63% or less.

  As shown in FIG. 2, the shoulder block row 7R includes a plurality of shoulder long edges 25a extending with the tire equator C side inclined to one side with respect to the tire circumferential direction (inclined to the left in FIG. 2), A plurality of shoulder short edges 25b, which are arranged between the shoulder long edges 25a, 25a adjacent to each other in the circumferential direction and are smaller in the tire circumferential direction than the shoulder long edges 25a, are configured. The shoulder short edge 25b of the present embodiment is the opening edge 4x of the shoulder lateral groove 4B. The shoulder long edge 25 a of the present embodiment is a block edge extending in the tire circumferential direction of the shoulder block 7. Thereby, the rigidity of the shoulder block 7 in the tire axial direction is largely ensured. Moreover, since the opening edge 4x of the shoulder lateral groove 4B is arranged in an area where the drainage resistance of the shoulder main groove 3B is large, the drainage in the shoulder main groove 3B is smoothly drained to the shoulder lateral groove 4B.

  As shown in FIG. 1, the shoulder block 7 is provided with a shoulder narrow groove 26 extending linearly continuously in the tire circumferential direction. Thus, the shoulder block 7 is divided into an inner block 7A disposed on the inner side in the tire axial direction than the shoulder narrow groove 26 and an outer block 7B disposed on the outer side in the tire axial direction from the inner block 7A. Such a shoulder narrow groove 26 exhibits a large edge effect in the tire circumferential direction and improves turning performance.

  When the groove width W6 of the shoulder narrow groove 26 is large, the rigidity of the inner block 7A or the outer block 7B in the tire axial direction is reduced, and the uneven wear resistance may be deteriorated. When the groove width W6 of the shoulder narrow groove 26 is small, the drainage performance may be reduced. For this reason, the groove width W6 of the shoulder narrow groove 26 is preferably 0.5 mm or more, more preferably 0.8 mm or more, and preferably 1.5 mm or less, more preferably 1.2 mm or less. From the same viewpoint, the depth D9 of the shoulder narrow groove 26 (shown in FIG. 3) is preferably 5.0 mm or more, more preferably 5.5 mm or more, and preferably 8.0 mm or less, more preferably 7.5 mm or less.

  In the present embodiment, the outer end of the inclined portion 13 a in the tire axial direction is connected to the shoulder narrow groove 26.

  As shown in FIG. 2, a siping 27 extending in the tire axial direction is provided on the center land portion 5, the middle block 6 inner block 7 </ b> A, and the outer block 7 </ b> B of the present embodiment. Such a siping 27 has an edge component in the tire axial direction, and further improves ice road performance. The siping 27 of the present embodiment has a semi-open type siping 27a having one end opened in the main groove 3A, 3B or the shoulder narrow groove 26 and the other end terminating in the center land portion 5 or each block 6, 7, and both ends. Is composed of an open-type siping 27b that opens in the center main groove 3A. In the present embodiment, the open type siping 27 b is provided only in the center land portion 5. As a result, the driving / braking force of the center land portion 5 to which a large ground pressure acts during straight traveling is increased, and in particular, straight running stability performance on an icy road is improved. In addition, the siping 27 of this embodiment is formed in linear form. As a result, the edge component in the tire axial direction is further increased, and ice road performance is further improved. The siping 27 is not limited to such a shape, and may be, for example, a wave shape.

  The siping 27 desirably has an angle α8 with respect to the tire axial direction of 0 to 30 ° in order to ensure a large driving force and braking force.

  The siping 27 provided in the center land portion 5 is not connected to the center notch portion 17 in this embodiment. Thereby, the rigidity of the center land part 5 is ensured high, and uneven wear-proof performance improves.

  The center land portion 5 and each of the blocks 6, 7 </ b> A, and 7 </ b> B are provided with a cross siping 28 that is orthogonal to the siping 27 and whose longitudinal size is smaller than that of the siping 27. Such a cross siping 28 includes an edge component in the tire circumferential direction, and improves turning performance. In the present embodiment, the cross siping 28 is provided in the center land portion 5 and each block 6, 7A, 7B in the outer region So in the tire axial direction, respectively, and the center land portion 5, each block 6, 7A, 7B. Two are arranged in each of the inner regions Si in the tire axial direction. Such a cross siping 28 equalizes the rigidity of the land portion 5 and the blocks 6, 7 </ b> A, and 7 </ b> B in the tire axial direction, and further ensures high anti-wear performance. In the present specification, for example, as shown in FIG. 4, in the middle block 6, the inner region Si is respectively located in the middle block 6 from the middle point Cp of the middle block 6 in the tire axial direction to both outer sides in the tire axial direction. The outer region So is a region on both outer sides in the tire axial direction of the inner region Si of the middle block 6 (center land portion 5, inner block 7A and In the case of the outer block 7B, it is defined by the region having the same ratio.)

  As shown in FIG. 2, although not particularly limited, the pitch Pa of the two cross sipings 28 and 28 provided in the inner region Si is set to a cross in order to effectively exhibit the above-described operation. 4 to 8% of the maximum width in the tire axial direction of the center land portion 5, the middle block 6 and the block portions 7A and 7B where the siping 28 is provided is desirable.

  In the present embodiment, as a winter tire, the total surface area Mb of all the land portions 5 and the tread surfaces of the blocks 6 and 7 and all the grooves 3A, 3B, 4A, and 4B of the tread portion 2 and the respective notches 17 and 23 24 and the sipings 27 and 28, the land ratio represented by the ratio (Mb / Ma) to the virtual surface area Ma of the virtual tread is set to 68 to 72%. Thereby, ice road performance, uneven wear resistance performance, and drainage performance are enhanced in a well-balanced manner.

  FIG. 5 shows a developed view of the tread portion 2 of another embodiment of the present invention. As shown in FIG. 5, a zigzag-shaped siping 30 is provided on the center land portion 5, the middle block 6, and the shoulder block 7. Such a siping 30 can exhibit edge effects in multiple directions and further improve the running performance on snowy roads.

  As mentioned above, although the pneumatic tire of this invention was demonstrated in detail, this invention is changed and implemented in various aspects, without being limited to said specific embodiment.

A pneumatic tire of size 195 / 80R15 having the basic pattern of FIG. 1 was prototyped based on the specifications of Table 1, and the drainage performance, ice road performance, and uneven wear resistance performance of each sample tire were tested. A pneumatic tire of size 195 / 80R15 having the basic pattern of FIG. 5 was prototyped based on the specifications in Table 2, and the drainage performance, ice road performance, and uneven wear resistance performance of each sample tire were tested. The common specifications for each tire are as follows. Except for the grooves described in Table 1 or 2, the groove width and angle of each groove are as shown in FIG. 1 or FIG.
Tread contact width TW: 162mm
<Each main groove>
Groove depth D1, D2: 12.5mm
<Horizontal groove>
Middle lateral groove depth D3: 9.0 mm
Groove depth D4 of the inclined part: 7.0 mm
Axial groove depth D5: 10.5mm
Shoulder narrow groove depth D9: 7.0 mm
<Others>
Inner middle notch depth D7: 9.0 mm
Outer middle notch depth D8: 9.0mm
Depth of each siping: 8.0mm
Depth of each cross siping: 4.0mm
Inner corners excluding sides formed by inner groove edges of the inner cutouts: Square shape: 100 °, 100 ° (Examples 1-7, Comparative Examples 1-7, Examples 1R-7R, Comparative Examples 1R-7R)
Triangular shape: 90 ° (Example 8, Example 8R)
Pentagon shape: 110 °, 110 °, 110 ° (Example 9, Example 9R)
The test method is as follows.

<Drainage performance>
Each sample tire was mounted on all wheels of a 2700cc four-wheel drive vehicle under the following conditions, and one driver took the test course on an asphalt road surface with a water depth of 2 to 5 mm. The driving characteristics at this time, such as steering response, rigidity, and grip, were evaluated by the driver's sensuality. The results are displayed with a score of 100 for Example 1 and Example 1R. The larger the value, the better. In addition, 95 or less is rejected.
Rims: 15 × 6.0J
Internal pressure: 350kPa (front wheel)
Internal pressure: 425 kPa (rear wheel)

<Ice performance>
With the above test vehicle, a driver on the icy road (ice barn) traveled with one driver, and characteristics relating to steering response, rigidity, grip, etc. were evaluated by sensory evaluation of the driver. The results are displayed with a score of 100 for Example 1 and Example 1R. The larger the value, the better. In addition, 95 or less is rejected.

<Uneven wear resistance>
In the above test vehicle, drive on a dry asphalt road for 10,000 km, and the wear amount of the land edge on both sides of the center land portion and the wear amount of the block edge on both sides of one middle block are the same in the tire circumferential direction. Measurements were made at eight locations on the tire circumference. Then, the difference between the maximum value and the minimum value of the wear amount was calculated. The results were expressed as an index with the reciprocal of the difference between Example 1 and Example 1R as 100. The larger the value, the better. In addition, 95 or less is rejected.
The test results are shown in Table 1.

  As a result of the test, in both Tables 1 and 2, it was confirmed that the tires of the examples had significantly improved drainage performance, ice road performance, and uneven wear resistance performance as compared with the comparative examples.

2 tread part 3A center main groove 5 center land part 7R shoulder block row 17 center notch part C tire equator

Claims (8)

A pair of center main grooves extending continuously in the tire circumferential direction on both sides in the tire axial direction of the tire equator on the tread portion, and a pair of shoulder main grooves extending continuously in the tire circumferential direction on the outer side in the tire axial direction of the center main groove. And a plurality of middle lateral grooves that connect between the center main groove and the shoulder main groove, and a plurality of shoulder lateral grooves that connect between the shoulder main groove and the grounding end,
A pair of middle blocks in which one center land portion divided by the pair of center main grooves, middle blocks divided by the center main grooves, the shoulder main grooves, and the middle lateral grooves are spaced apart in the tire circumferential direction. A pneumatic tire comprising a row and a pair of shoulder block rows in which the shoulder block divided by the shoulder main groove, the ground contact end and the shoulder lateral groove is spaced in the tire circumferential direction;
The center main groove is arranged between a plurality of center long side portions inclined to one side with respect to the tire circumferential direction and the center long side portions adjacent to each other in the tire circumferential direction, and is more tire than the center long side portion. A plurality of center short sides with small circumferential lengths are alternately arranged,
The center land portion is provided with a center notch portion extending from the center main groove to the tire equator side and terminating in the center land portion,
The center notch is
10-15% in the tire axial direction of the maximum length of the maximum length in the tire axial direction is the center land portion,
The length of the opening edge in the tire circumferential direction is 10 to 15% of one pitch of the shoulder block row, and
55 to 65% depth of the groove depth of the center main groove, and,
Provided including the intersection of the center long side part and the center short side part,
The shoulder main groove connects between a plurality of shoulder long sides inclined to one side with respect to the tire circumferential direction and shoulder long sides adjacent to each other in the tire circumferential direction, and the tire circumference is longer than the shoulder long sides. It is formed in a zigzag shape with alternating shoulder short sides with a small length in the direction,
The middle block is provided with an outer middle notch extending from the shoulder main groove to the tire equator side and terminating in the middle block,
Wherein the outer middle notch, the pneumatic tire according to claim Rukoto provided in the shoulder short side.   The pneumatic tire according to claim 1, wherein the center notch has a polygonal shape with four or more sides in plan view. The middle block is provided with an inner middle notch extending from the center main groove outward in the tire axial direction and terminating in the middle block,
The pneumatic tire according to claim 1 , wherein the inner middle notch portion is provided in the center short side portion .   The land ratio, which is the ratio of the total surface area of the tread surface of the tread part and the virtual surface area of the virtual tread surface obtained by filling all the grooves of the tread part, is 68 to 72%. Pneumatic tire described in 2. A middle outer block edge extending in the tire axial direction outer side and the tire circumferential direction of the middle block includes a middle outer short edge portion inclined to the other side opposite to one side with respect to the tire circumferential direction, and the middle outer short edge. A pair of middle outer long edges that are inclined from the opposite ends of the middle portion to the opposite side of the middle outer short edge and have a larger length in the tire circumferential direction than the middle outer short edge,
The pneumatic tire according to any one of claims 1 to 4, wherein the outer middle notch portion has a notch edge that smoothly extends the middle outer long edge portion.
The shoulder block row is arranged between a plurality of shoulder long edges extending from the tire equator side to one side with respect to the tire circumferential direction, and the shoulder long edges adjacent to each other in the tire circumferential direction. Including a plurality of shoulder short edges having a small length in the tire circumferential direction,
The shoulder lateral grooves, the pneumatic tire according to any one of the shoulder main grooves has a groove bottom at a position shallower than and the claims 1 to 5 that are open at the shoulder short edges. The land portion edge extending in the tire circumferential direction of the center land portion is formed between the center long edge portion extending along the center long side portion and the center long edge portion adjacent in the tire circumferential direction. Including
The middle inner block edge extending in the tire axial direction inner side and the tire circumferential direction of the middle block includes a middle inner short edge portion inclined to the other side opposite to one side with respect to the tire circumferential direction, and the middle inner short edge. A pair of middle inner long edge portions that are inclined from the opposite ends of the middle portion to the opposite side of the middle inner short edge portion and have a larger length in the tire circumferential direction than the middle inner short edge portion,
The center short edge portion is provided with an overlapping portion that overlaps the middle inner short edge portion in the tire circumferential direction,
The pneumatic tire according to any one of claims 1 to 6, wherein an arrangement pitch of the center short edge portion and an arrangement pitch of the middle inner short edge portion are the same.
The middle block is provided with an inner middle notch extending from the center main groove outward in the tire axial direction and terminating in the middle block,
The pneumatic tire according to claim 7, wherein the inner middle notch portion has a notch edge that smoothly extends the middle inner long edge portion .

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