JP6438329B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that can achieve a high level of performance on ice, performance on snow, and steering stability on a dry road surface.

  Conventionally, in order to improve performance on ice, for example, a pneumatic tire in which a block arranged in a tread portion is divided into a plurality of block pieces by a plurality of sipings extending in the tire axial direction has been proposed (for example, See Patent Document 1 below). Such a pneumatic tire can use the edges of the block small pieces to increase the frictional force with the ice road surface, and can improve the driving force and braking force.

JP 2009-190677 A

  However, the pneumatic tire as described above has a problem in that the rigidity of each block is lowered, and therefore, on snowy roads and dry roads, the response to steering is reduced and the swaying when lane changes are likely to increase. was there.

  In order to increase the rigidity of the block, it is conceivable to reduce the number of sipings and increase the land ratio, but the problem is that the performance on ice and the performance on snow are likely to deteriorate due to a decrease in edge components and groove area. was there.

  The present invention has been devised in view of the above circumstances, and at least one of the blocks is constituted by a large block whose length in the tire circumferential direction is limited to a predetermined range, and a large block tire. On the ice, the tire circumferential direction length of the pair of outer block pieces constituting the outer side in the circumferential direction and the inner block piece arranged between the pair of outer block pieces is limited to a predetermined range. The main purpose is to provide a pneumatic tire capable of achieving a high level of performance, performance on snow, and driving stability on a dry road surface.

The invention described in claim 1 is a pneumatic tire having a plurality of main grooves extending continuously in the tire circumferential direction and a plurality of land portions divided by the main grooves in the tread portion. And
The land portion extends in a direction intersecting with the main groove and is provided with a plurality of transverse grooves that are spaced apart in the tire circumferential direction, so that blocks separated by the transverse grooves are spaced apart in the tire circumferential direction. The land ratio Sb / Sa expressed by the ratio of the total area Sb of the treads of all blocks and the total surface area Sa of the tread obtained by filling all the grooves of the tread portion is 60% to 80%. At least one of the blocks has a tire circumferential direction maximum length in the tire circumferential direction of a contact surface when a normal load is applied to a normal state tire that is assembled with a normal rim and filled with a normal internal pressure. The large block is provided with a plurality of sipings extending at an angle of 0 to 20 degrees with respect to the tire axial direction. A plurality of block pieces divided by siping are provided, and the block pieces are arranged between a pair of outer block pieces constituting both sides of the large block in the tire circumferential direction and at least a pair of the outer block pieces. A length L1 in the tire circumferential direction of the outer block piece is 5% to 12% of a maximum length in the tire circumferential direction of the ground contact surface, and the tire circumference of the inner block piece is The length L2 in the direction is 3.5 to 15.0 mm.

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the large block is provided with 4 to 11 sipings.

  According to a third aspect of the present invention, the block row is composed of at least one center block row composed of a center block disposed on the tire equator side and a shoulder block disposed on the tread grounding end side. The center block is composed of the large block, and the number of the shoulder blocks included in each shoulder block column is equal to the number of the center blocks included in each center block column. The pneumatic tire according to claim 1 or 2, which is 200% to 500%.

  The invention according to claim 4 is the pneumatic tire according to any one of claims 1 to 3, wherein a width of the lateral groove is 2.2 to 12.0 mm.

  In the invention according to claim 5, the land portion is provided with at least one narrow groove extending in the tire circumferential direction, and the large blocks are disposed on both sides of the narrow groove in the tire axial direction. The large blocks that are adjacent to each other through the narrow groove are arranged so as to be displaced in the tire circumferential direction, and the positional deviation length in the tire circumferential direction between the large blocks is the length of the large block in the tire circumferential direction. The pneumatic tire according to any one of claims 1 to 4, which is 10% to 30%.

According to a sixth aspect of the present invention, the inner block piece includes a first inner block piece disposed at a center of the block in the tire circumferential direction, and the first inner block piece and the outer block piece. Including the second inner block piece, the length L1 of the outer block piece, the length L2i in the tire circumferential direction of the first inner block piece, and the tire circumferential length of the second inner block piece. L2o is the pneumatic tire according to any one of claims 1 to 5, which satisfies a relationship of the following formula (1).
L2i <L1 <L2o (1)

  In the present specification, unless otherwise specified, the size of each part of the tire is a value specified in a normal state with no load loaded with a normal rim and filled with a normal internal pressure.

  The “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, JAMMA is a standard rim, TRA is “Design Rim”, or ETRTO. Then means "Measuring Rim".

  The “regular internal pressure” is the air pressure defined by the standard for each tire. The maximum air pressure for JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for ETRA, If so, use "INFLATION PRESSURE".

  The pneumatic tire of the present invention has a plurality of main grooves extending continuously in the tire circumferential direction in the tread portion and a plurality of land portions divided by the main grooves. The land portion extends in a direction intersecting with the main groove and is provided with a plurality of horizontal grooves spaced in the tire circumferential direction, so that a block row in which blocks divided by the horizontal grooves are spaced in the tire circumferential direction is provided. Provided.

  Such a block pattern, for example, can increase the amount of bite into the snow road, can smoothly guide the water film between the tread portion and the road surface, and can improve on-snow performance and drainage performance.

  Moreover, the land ratio Sb / Sa represented by the ratio of the total area Sb of the treads of all the blocks and the total surface area Sa of the tread obtained by filling all the grooves in the tread portion is limited to 60% to 80%. . Thereby, since the tread part can balance the contact area with the road surface and the groove area, it is possible to achieve both the steering stability performance on the dry road surface, the performance on snow, and the drainage performance.

  Furthermore, at least one of the blocks has a tire circumferential length that is the maximum length in the tire circumferential direction of the contact surface when a normal load is applied to a normal tire that is assembled with a normal rim and filled with normal internal pressure. It consists of large blocks that are 25% to 90% of the total.

  Such a large block can maintain the drainage performance because the lateral grooves arranged on both sides of the large block in the tire circumferential direction can be surely arranged in the ground contact surface while enhancing the rigidity in the tire circumferential direction. On the other hand, it is possible to improve the performance on snow and the stable driving performance on the dry road.

  The large block is provided with a plurality of sipings extending at an angle of 0 to 20 degrees with respect to the tire axial direction on the tread surface, thereby providing a plurality of block pieces segmented by the siping. Such a block piece can make use of its edge to increase the frictional force with the ice road surface and improve the performance on ice.

  The block small piece includes a pair of outer block small pieces constituting both sides of the large block in the tire circumferential direction and at least one inner block small piece disposed between the pair of outer block small pieces. The length L1 of the outer block piece in the tire circumferential direction is 5% to 12% of the maximum length in the tire circumferential direction of the contact surface, and the length L2 of the inner block piece in the tire circumferential direction is 3.5 to Set to 15.0 mm.

  Since the outer block piece and the inner block piece can maintain the edge component and increase the rigidity in the tire circumferential direction compared to the conventional block piece, the performance on the snow while maintaining the performance on ice. And, the steering stability performance on the dry road surface can be effectively improved.

It is an expanded view of the tread part of the pneumatic tire of this embodiment. It is AA sectional drawing of FIG. It is an enlarged view of a center block row. It is an enlarged view of a shoulder block row.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a studless tire for heavy-duty vehicles such as trucks and buses, for example, as a pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment. The tread portion 2 of the tire 1 is provided with a plurality of main grooves 3 extending continuously in the tire circumferential direction and a plurality of land portions 4 divided by the main grooves 3.

  The main groove 3 includes a center main groove 3A extending on the tire equator C, and a pair of shoulder main grooves 3B and 3B arranged on the tread grounding end 2e side with respect to the center main groove 3A.

  Here, the tread grounding end 2e is an edge when it can be identified by a clear edge in appearance, but when such an edge cannot be identified, a normal load is applied to the tire in the normal state. It is determined as a position where the tread portion 2 contacts the flat surface at the outermost side in the tire axial direction when the tread portion 2 contacts the flat surface with a camber angle of 0 °.

  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. The maximum load capacity is specified for JATMA, and the table “TIRE LOAD LIMITS” is set for TRA. The maximum value described in "AT VARIOUS COLD INFLATION PRESSURES", or "LOAD CAPACITY" for ETRTO.

  The center main groove 3A and the shoulder main groove 3B are formed, for example, as straight grooves extending continuously in the tire circumferential direction. Each of the main grooves 3A and 3B can smoothly guide the water film between the tread portion 2 and the road surface in the tire circumferential direction, and can compress the snow in the groove to obtain a large snow column shear force. It is possible to improve drainage performance and on-snow performance.

  In order to effectively exhibit the above action, the groove width W1 of the center main groove 3A and the shoulder main groove 3B is preferably about 2.5% to 4.0% of the tread width TW, and each groove depth. The length D1 (shown in FIG. 2) is preferably about 8% to 10% of the tread width TW. The tread width TW is a tire axial distance between the tread grounding ends 2e and 2e in the normal state.

  The land portion 4 includes a pair of inner land portions 4A and 4A formed between the center main groove 3A and the shoulder main groove 3B, and a pair of shoulder main grooves 3B and the tread grounding end 2e. The outer land portion 4B is included.

  The inner land portion 4A and the outer land portion 4B have a narrow groove 5 extending continuously in the tire circumferential direction and a plurality of lateral grooves 6 extending in the direction intersecting with the main groove 3 and spaced apart in the tire circumferential direction. And are provided. Thereby, in each land part 4A, 4B, the block row | line | column 8 by which the block 7 divided by the narrow groove 5 and the horizontal groove 6 was spaced apart by the tire circumferential direction is formed.

  Such a block pattern can increase the amount of bite into the snow road, can smoothly guide the water film between the tread portion 2 and the road surface, and is useful for improving the performance on snow and the drainage performance.

  In order to effectively exhibit the above-described action, a land represented by a ratio between the total area Sb of the treads 2s of all the blocks 7 and the total surface area Sa of the tread obtained by filling all the grooves of the tread portion 2 is obtained. The ratio Sb / Sa is preferably set to 60% to 80%. Thereby, since the contact area with the road surface and the groove area are balanced, the tread portion 2 can achieve both the steering stability performance on the dry road surface, the performance on snow, and the drainage performance.

  If the land ratio Sb / Sa exceeds 80%, the groove area cannot be maintained, and there is a possibility that the performance on the snow and the drainage performance cannot be sufficiently improved. On the other hand, if the land ratio Sb / Sa is less than 60%, the contact area with the road surface cannot be maintained, and there is a possibility that the steering stability performance on the dry road surface and the performance on ice cannot be sufficiently improved. From such a viewpoint, the land ratio Sb / Sa is more preferably 75% or less, and more preferably 65% or more.

  The narrow groove 5 includes a center narrow groove 5A extending between the center main groove 3A and the shoulder main groove 3B, and a shoulder narrow groove 5B extending between the shoulder main groove 3B and the tread grounding end 2e.

  The center narrow groove 5A and the shoulder narrow groove 5B are formed as straight grooves, like the main groove 3, and can improve drainage performance and snow performance while maintaining the rigidity of the land portions 4A, 4B. The groove width W2 of each of the narrow grooves 5A and 5B is preferably about 0.5% to 2.0% of the tread width TW, and the groove depth D2 (shown in FIG. 2) is the tread width TW. About 4% to 6%.

  The lateral groove 6 includes an inner center lateral groove 6Ai extending between the center main groove 3A and the center narrow groove 5A, a center center lateral groove 6Ac extending between the center narrow groove 5A and the shoulder main groove 3B, and a shoulder main groove 3B and the shoulder narrow groove. An outer center lateral groove 6Ao extending between the groove 5B and a shoulder lateral groove 6B extending between the shoulder narrow groove 5B and the tread grounding end 2e are included.

  The inner center lateral groove 6Ai, the center center lateral groove 6Ac, the outer center lateral groove 6Ao, and the shoulder lateral groove 6B can compress snow in the groove to obtain a snow column shear force, and each of the land portions 4A, 4B and the road surface. Since the water film between the two can be guided in the tire axial direction, the performance on snow and the drainage performance can be improved.

  In order to effectively exhibit such an action, the groove width W3 of the inner center lateral groove 6Ai, the center center lateral groove 6Ac, the outer center lateral groove 6Ao, and the shoulder lateral groove 6B is preferably 2.2 to 12.0 mm. If the groove width W3 is less than 2.2 mm, the traction performance on snowy roads and the drainage performance may not be sufficiently improved. On the contrary, even if the groove width W3 exceeds 12.0 mm, the length in the tire circumferential direction of each block 7 is reduced and the rigidity of the block 7 is reduced. Therefore, the performance on snow and the dry road surface There is a possibility that the steering stability performance cannot be improved sufficiently. From such a viewpoint, the groove width W3 is more preferably 4.0 mm or more, and more preferably 11.0 mm or less.

  From the same viewpoint, the groove depth D3 (shown in FIG. 2) of the inner center lateral groove 6Ai, the center center lateral groove 6Ac, the outer center lateral groove 6Ao, and the shoulder lateral groove 6B is preferably 10.0 mm or more, more preferably 12.0 mm. The above is desirable, preferably 18.0 mm or less, and more preferably 16.0 mm or less.

  Further, the inner center lateral groove 6Ai, the center center lateral groove 6Ac, the outer center lateral groove 6Ao, and the shoulder lateral groove 6B of the present embodiment are arranged so as to be displaced in the tire circumferential direction from the lateral grooves adjacent in the tire axial direction. Thereby, since each horizontal groove 6Ai, 6Ac, 6Ao, and 6B is arrange | positioned uniformly in a tire peripheral direction, the pitch noise during driving | running | working can be disperse | distributed, improving drainage performance and on-snow performance effectively.

  The block row 8 includes at least one center block 7A arranged on the tire equator C side, in the present embodiment, six center block rows 8A and a shoulder block 7B arranged on the tread ground contact end 2e side. It consists of a pair of shoulder block rows 8B that are configured.

  The center block 7A is divided by a pair of inner center block 7Ai, center narrow groove 5A, shoulder main groove 3B, and central center lateral groove 6Ac, which are divided by a center main groove 3A, a center narrow groove 5A, and an inner center lateral groove 6Ai. And a pair of outer center blocks 7Ao divided by a shoulder main groove 3B, a shoulder narrow groove 5B, and an outer center lateral groove 6Ao.

  Accordingly, the center block row 8A has a pair of inner center block rows 8Ai in which the inner center block 7Ai is spaced in the tire circumferential direction, and a pair of center center blocks in which the center center block 7Ac is spaced in the tire circumferential direction. A pair of outer center block rows 8Ao in which the row 8Ac and the outer center block 7Ao are spaced apart in the tire circumferential direction are included.

  As shown in FIG. 3 in an enlarged manner, the inner center block 7Ai, the center center block 7Ac, and the outer center block 7Ao have a length L5 in the tire circumferential direction larger than a width W5 in the tire axial direction. It is formed in a vertically long rectangular shape. Each of such blocks 7Ai, 7Ac, and 7Ao can increase the rigidity in the tire circumferential direction, and can improve performance on snow and steering stability performance on a dry road surface.

  Further, the inner center block 7Ai, the center center block 7Ac, and the outer center block 7Ao have a length L5 in the tire circumferential direction that is the contact surface Gs when the regular load is applied to the tire 1 in the normal state (see FIG. 1). The large block 11 is 25% to 90% of the maximum tire circumferential length L6 (shown in FIG. 1).

  The inner center block 7Ai, the center center block 7Ac, and the outer center block 7Ao made up of such large blocks 11 are arranged on both sides in the tire circumferential direction of each block 7Ai, 7Ac, 7Ao while effectively increasing the rigidity in the tire circumferential direction. Since the horizontal groove 6 can be reliably arranged in the ground contact surface Gs, it is possible to improve the performance on snow and the steering stability performance on the dry road surface while maintaining the drainage performance.

  When the length ratio L5 / L6 is less than 25%, the rigidity in the tire circumferential direction of the inner center block 7Ai, the center center block 7Ac, and the outer center block 7Ao cannot be sufficiently increased, and the performance on snow. In addition, there is a risk that the steering stability performance on the dry road surface cannot be fully exhibited. On the other hand, if the ratio L5 / L6 exceeds 90%, the lateral groove 6 cannot be reliably disposed in the ground contact surface Gs, and there is a possibility that the traction performance and the drainage performance on the snowy road cannot be sufficiently exhibited. From such a viewpoint, the ratio L5 / L6 is more preferably 35% or more, and more preferably 85% or less.

  The ratio Sc / Sb between the total area Sc of the tread surface 2s of the center block 7A and the total area Sb of the tread surface 2s of all the blocks 7 is preferably 60% to 90%. As a result, the tread portion 2 can maintain the ratio of the lateral groove 6 arranged on the ground contact surface Gs while increasing the ratio of the large block 11, and achieves both on-snow performance, steering stability performance on a dry road surface, and drainage performance. sell.

  If the ratio Sc / Sb is less than 60%, the large block 11 cannot be sufficiently disposed in the tread portion 2, and it may not be possible to sufficiently improve the performance on snow and the driving stability performance on a dry road surface. is there. On the contrary, if the ratio Sc / Sb exceeds 90%, the ratio of the lateral grooves 6 arranged on the ground contact surface Gs is reduced, and there is a possibility that the traction performance on the snowy road and the drainage performance are deteriorated. From such a viewpoint, the ratio Sc / Sb is more preferably 65% or more, and more preferably 85% or less.

  The inner center block 7Ai, the central center block 7Ac, and the outer center block 7Ao are provided with a plurality of sipings S1 extending on the tread surface 2s at an angle of 0 to 20 degrees with respect to the tire axial direction. Thereby, each block 7Ai, 7Ac, 7Ao is provided with a plurality of block small pieces 12 divided by siping S1.

  Such a block small piece 12 can reduce the rigidity in the tire circumferential direction of the inner center block 7Ai, the center center block 7Ac, and the outer center block 7Ao to increase the ground contact area, and can use the edge in the tire axial direction. Can improve performance on ice.

  In order to effectively exhibit the above action, it is desirable to provide 4 to 11 sipings S1. If the number of sipings S1 is less than 4, the edge in the tire axial direction cannot be used, and the performance on ice may not be sufficiently improved. On the other hand, when the number of sipings S1 exceeds 11, the rigidity of each block 7Ai, 7Ac, 7Ao is excessively lowered, and there is a possibility that the performance on snow and the steering stability performance on a dry road surface may be lowered. From such a viewpoint, the siping S1 is more preferably 5 or more, and more preferably 8 or less.

  The block small piece 12 includes at least one outer block small piece 12A, 12A that constitutes both sides of each center block 7Ai, 7Ac, 7Ao in the tire circumferential direction, and the pair of outer block small pieces 12A, 12A. In the present embodiment, three inner block pieces 12B are included.

  Further, the length L1 in the tire circumferential direction of the outer block small piece 12A is set to 5% to 12% of the maximum length L6 in the tire circumferential direction of the ground contact surface Gs (shown in FIG. 1), and the inner block small piece 12B. The length L2 in the tire circumferential direction is set to 3.5 to 15.0 mm.

  Such outer block small piece 12A and inner block small piece 12B can increase the rigidity in the tire circumferential direction as compared with the conventional block small piece while maintaining the edge component. The performance and the driving stability performance on the dry road surface can be effectively improved.

  When the length ratio L1 / L6 (shown in FIG. 1) is less than 5%, the rigidity in the tire circumferential direction of the outer block small piece 12A is reduced, and the performance on snow and the steering stability performance on the dry road surface are improved. There is a possibility that it cannot be improved sufficiently. On the other hand, if the ratio L1 / L6 exceeds 12%, the siping S1 cannot be sufficiently provided, and the on-ice performance may not be improved. From such a viewpoint, the ratio L1 / L6 is more preferably 6% or more, and more preferably 11% or less.

  Similarly, the length L2 of the inner block piece 12B is more preferably 5 mm or more, and more preferably 12 mm or less.

  Further, the inner block piece 12B of the present embodiment is arranged between the first inner block piece 12Bi and the first inner block piece 12Bi and the outer block piece 12A arranged at the center in the tire circumferential direction of the center block 7A. Second inner block piece 12Bo.

Furthermore, the length L1 of the outer block piece 12A, the length L2i in the tire circumferential direction of the first inner block piece 12Bi, and the length L2o in the tire circumferential direction of the second inner block piece 12Bo are expressed by the following formula (1). Satisfy the relationship.
L2i <L1 <L2o (1)

  Thereby, each block 7Ai, 7Ac, 7Ao maintains the rigidity of the outer block small piece 12A, and the siping S1 is formed at both ends in the tire circumferential direction of each block 7Ai, 7Ac, 7Ao. The performance on ice can be greatly improved while suppressing uneven wear such as wear.

  In the present embodiment, the inner center block 7Ai and the center center block 7Ac are arranged adjacent to each other via the center narrow groove 5A. As a result, the blocks 7Ai and 7Ac can support each other in contact with each other during turning in which a large lateral force is applied, thereby increasing the lateral rigidity of the inner land portion 4A. Stability performance can be improved.

  Further, the inner center block 7Ai and the center center block 7Ac are arranged so as to be displaced in the tire circumferential direction. Thereby, since each block 7Ai and 7Ac is arrange | positioned uniformly in a tire peripheral direction in the tread part 2, the performance on ice and the steering stability performance on a dry road surface can be improved.

  In order to effectively exhibit such an action, the positional deviation length L7 in the tire circumferential direction between the inner center block 7Ai and the central center block 7Ac is 10% of the length L5 in the tire circumferential direction of the blocks 7Ai and 7Ac. ~ 30% is desirable. The length ratio L7 / L5 is preferably 10 to 30%. If the ratio L7 / L5 is less than 10%, the blocks 7Ai and 7Ac may not be arranged uniformly in the tire circumferential direction. On the contrary, when the ratio L7 / L5 exceeds 30%, the inner center lateral groove 6Ai and the center center lateral groove 6Ac arranged on both sides in the tire circumferential direction of each block 7Ai, 7Ac are greatly separated in the tire circumferential direction, Performance and drainage performance may not be improved sufficiently. From such a viewpoint, the ratio L7 / L5 is more preferably 15% or more, and more preferably 25% or less.

  As shown in FIG. 4, the outer center block 7Ao is disposed adjacent to the shoulder block 7B via the shoulder narrow groove 5b. Thereby, like inner center block 7Ai and center center block 7Ac, each block 7Ao and 7B touches and supports each other, and can improve the lateral rigidity of outer land part 4B.

  The shoulder block 7B is formed by being divided by a shoulder narrow groove 5B, a tread grounding end 2e, and a shoulder lateral groove 6B. Further, the shoulder block 7B is formed in a horizontally-long rectangular shape having a slightly larger width W8 in the tire axial direction than its circumferential length L8.

  Such a shoulder block 7B can exhibit a large rigidity against a lateral force generated at the time of turning, and can improve performance on snow and steering stability performance on a dry road surface. The width W8 of the shoulder block 7B is preferably about 8% to 12% of the tread width TW (shown in FIG. 1), and the circumferential length L8 is about 10% to 14% of the tread width TW. desirable.

  The number N1 of shoulder blocks 7B included in each shoulder block row 8B is preferably larger than the number N2 of center blocks 7A included in each center block row 8A (N1> N2). Thereby, since the number of the shoulder lateral grooves 6B formed in the shoulder block row 8B is relatively large, the snow column shear force is reduced on the tread ground contact end 2e side that greatly affects the steering stability performance on the snowy road. It can be obtained effectively and the performance on snow can be greatly improved.

  In order to effectively exhibit such an action, the ratio N1 / N2 between the number N1 of the shoulder blocks 7B and the number N2 of the center blocks 7A is preferably 200% to 500%. If the ratio N1 / N2 is less than 200%, the shoulder lateral grooves 6B cannot be sufficiently provided, and there is a possibility that sufficient snow column shear force cannot be obtained. On the other hand, if the ratio N1 / N2 exceeds 500%, the rigidity of the shoulder block 7B becomes small, and the steering stability performance on the dry road surface may not be sufficiently improved. From such a viewpoint, the ratio N1 / N2 is more preferably 250% or more, and more preferably 400% or less.

  The shoulder block 7B has a longitudinal siping S2 extending on the tread ground surface 2e side in the tire circumferential direction on the tread surface 2s, and at least one extending in the tire axial direction between the shoulder narrow groove 5B and the longitudinal siping S2. In the embodiment, one horizontal siping S3 is provided. Thereby, the shoulder block 7B is provided with three block small pieces 13 divided by the vertical siping S2 and the horizontal siping S3.

  The block small piece 13 is arranged on the tread grounding end 2e side with respect to the vertical siping S2 and on the inner side in the tire axial direction with respect to the vertical block small piece 13A. It consists of a pair of horizontally long block pieces 13B and 13B arranged on both sides in the direction.

  Such a vertically long block piece 13A can partially reduce the rigidity of the shoulder block 7B on the outer side in the tire axial direction while utilizing the edge in the tire circumferential direction, and is effective in performance on ice and snow and wandering performance. Can be increased. In addition, the horizontally long block small pieces 13B and 13B can reduce the rigidity of the shoulder block 7B in the tire circumferential direction to increase the ground contact area, and can use the edge in the tire axial direction to improve the performance on ice. .

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

Tires having the basic structure shown in FIG. 1 and having block pieces and sipings shown in Table 1 were manufactured, and their performance was evaluated. The common specifications are as follows.
Tire size: 11R22.5 16PR
Rim size: 22.5 × 7.50
Tread width TW: 260mm
Main groove:
Groove width W1: 9.0 mm, ratio W1 / TW: 3.5%
Groove depth D1: 20.0 mm, ratio D1 / TW: 7.7%
Narrow groove:
Groove width W2: 2.0 mm, groove depth D2: 12.0 mm
Ratio W2 / TW: 0.8%, Ratio D2 / TW: 4.6%
Horizontal groove:
Groove depth D3: 14.5 mm, ratio D3 / TW: 5.6%
contact area:
Maximum tire circumferential length L6: 240mm
Center block:
Width W5: 26mm, ratio W5 / TW: 10%
Shoulder block
Width W8: 26 mm, ratio W8 / TW: 10%,
Circumferential length L8: 27.5 mm, ratio L8 / TW: 10.6%
Siping
Width: 0.6mm, depth: 10.0mm
The test method is as follows.

<Performance on ice>
Each test tire is assembled on the rim, filled with an internal pressure of 800 kPa, mounted on all wheels of an 8.5-pile 2-D vehicle, and half loaded (front wheel load: 26.72 kN, rear wheel load: 11. In a test course on an icy road (road surface temperature -2 to 0 degrees) in a state of 38 kN), the feeling when starting and accelerating from a vehicle stop state was evaluated by the sensuality of a professional test driver. The result is displayed with a score of 100 as a comparative example. The larger the value, the better.

<Snow performance (traction)>
Each test tire is assembled on the rim under the above conditions and mounted on all the wheels of the vehicle. Feeling when starting and accelerating from a vehicle stop state on a sherbet-like snowy road in an environment with a temperature of 0 ° C Was evaluated by the sensuality of professional test drivers. The result is displayed with a score of 100 as a comparative example. The larger the value, the better.

<Snow performance (turning)>
Each test tire is assembled on the rim under the above conditions, mounted on all the wheels of the vehicle, and on the sherbet-like snowy road in an environment with a temperature of 0 ° C. It evaluated by sensory evaluation. The result is displayed with a score of 100 as a comparative example. The larger the value, the better.

<Operation stability on dry road>
Each test tire is assembled on the rim under the above conditions, mounted on all the wheels of the vehicle, and travels at a speed of 80 km / h on a dry asphalt road test course, with characteristics related to straightness, steering performance, responsiveness, etc. It was evaluated by sensory evaluation of the driver. The result is displayed with a score of 100 as a comparative example. The larger the value, the better.

<Drainage performance>
Each test tire is assembled on the rim under the above conditions, mounted on all the wheels of the vehicle, and the speed is increased stepwise on a course with a 100m radius asphalt road surface with a water depth of 5mm and a length of 20m. The vehicle was allowed to enter the vehicle, the lateral acceleration (lateral G) was measured, and the average lateral G of the front wheels at a speed of 50 to 80 km / h was calculated. The results were expressed as an index with the average lateral G of the comparative example as 100. The larger the value, the better.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the tires of the examples can achieve a high level of compatibility on ice performance, snow performance, and driving stability performance on a dry road surface.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Main groove 4 Land part 6 Horizontal groove 7 Block 11 Large block 12A Outer block small piece 12B Inner block small piece

Claims (6)

A pneumatic tire having a plurality of main grooves extending continuously in the tire circumferential direction on the tread portion and a plurality of land portions divided by the main grooves,
The land portion extends in a direction intersecting with the main groove and is provided with a plurality of transverse grooves that are spaced apart in the tire circumferential direction, so that blocks separated by the transverse grooves are spaced apart in the tire circumferential direction. Including columns,
The land ratio Sb / Sa represented by the ratio of the total area Sb of the treads of all the blocks and the total surface area Sa of the tread obtained by filling all the grooves of the tread portion is 60% to 80%,
At least one of the blocks has a tire circumferential direction maximum length in the tire circumferential direction of a contact surface when a normal load is applied to a normal tire in which a normal rim is assembled and filled with a normal internal pressure. Of large blocks that are 25% to 90% of
In this large block, a plurality of block pieces divided by the siping are provided by providing a plurality of sipings extending at an angle of 0 to 20 degrees with respect to the tire axial direction on the tread.
The block small piece includes a pair of outer block small pieces constituting both sides in the tire circumferential direction of the large block, and at least one inner block small piece arranged between the pair of outer block small pieces,
A length L1 of the outer block piece in the tire circumferential direction is 5% to 12% of the maximum length of the ground contact surface in the tire circumferential direction,
The pneumatic tire according to claim 1, wherein a length L2 of the inner block piece in the tire circumferential direction is 3.5 to 15.0 mm.   The pneumatic tire according to claim 1, wherein the large block is provided with 4 to 11 sipings. The block row is composed of at least one center block row composed of center blocks arranged on the tire equator side, and a pair of shoulder block rows constituted of shoulder blocks arranged on the tread grounding end side,
The center block is composed of the large block,
The pneumatic tire according to claim 1 or 2, wherein the number of the shoulder blocks included in each shoulder block row is 200% to 500% of the number of the center blocks included in each center block row.   The pneumatic tire according to any one of claims 1 to 3, wherein a groove width of the lateral groove is 2.2 to 12.0 mm. At least one narrow groove extending in the tire circumferential direction is arranged in the land portion,
The large blocks are arranged on both sides of the narrow groove in the tire axial direction,
The large blocks that are adjacent to each other through the narrow grooves are arranged so as to be displaced in the tire circumferential direction,
The pneumatic tire according to any one of claims 1 to 4, wherein a positional deviation length in the tire circumferential direction between the large blocks is 10% to 30% of a length in the tire circumferential direction of the large blocks. The inner block piece includes a first inner block piece arranged at the center of the tire in the tire circumferential direction, and a second inner block piece arranged between the first inner block piece and the outer block piece. ,
The length L1 of the outer block piece, the length L2i in the tire circumferential direction of the first inner block piece, and the length L2o in the tire circumferential direction of the second inner block piece have the relationship of the following formula (1). The pneumatic tire according to any one of claims 1 to 5, which is satisfied.
L2i <L1 <L2o (1)

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