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EP-4570526-B1 - PNEUMATIC TIRE

EP4570526B1EP 4570526 B1EP4570526 B1EP 4570526B1EP-4570526-B1

Inventors

  • MATSUBARA, KEISUKE

Dates

Publication Date
20260513
Application Date
20241206

Claims (9)

  1. A pneumatic tire (1) with a tread (10), wherein the tread (10) comprises: a pair of shoulder regions (40), each shoulder region (40) being disposed on an outer side, in a tire axial direction, of a corresponding one of a pair of shoulder main grooves (30) continuously extending in a tire circumferential direction, and being delimited by a corresponding one of a pair of ground contact edges; and a center region (50) disposed between the pair of shoulder regions; wherein a plurality of blocks are arranged in the center region (50) and the shoulder regions (40); and in a plan view of the tread (10), an area of a largest block having a maximum area among the blocks arranged in the center region (50) and the shoulder regions (40) is less than or equal to 1.4 times of an area of a smallest block having a minimum area, and wherein the center region (50) comprises: a center block (51) formed in a substantially polygonal shape and arranged at a distance from the shoulder main groove (30); a middle block (52,53) arranged around the center block (51); an annular groove (54) formed in a substantially polygonal shape and defined to border the center block (51); a center longitudinal groove (55) defined to connect annular grooves (54) which are adjacent to each other in the tire circumferential direction; and a plurality of center lateral grooves (56,57) defined to connect the annular grooves (54) to the shoulder main groove (30), characterized in that among the plurality of center lateral grooves (56,57), center lateral grooves (56,57) adjacent to each other in the tire circumferential direction are inclined relative to the tire axial direction along opposite directions.
  2. The pneumatic tire (1) according to claim 1, wherein the center block (51) has a substantially hexagonal shape.
  3. The pneumatic tire (1) according to claim 1, wherein none of the blocks arranged in the center region (50) and the shoulder regions (40) has a sipe or a slit.
  4. The pneumatic tire (1) according to claim 1 or 2, wherein the largest block is arranged in the shoulder region (40).
  5. The pneumatic tire (1) according to claim 1, wherein an area of the center block (51) is greater than or equal to 0.85 times of the area of the largest block.
  6. The pneumatic tire (1) according to claim 1, wherein the annular groove (54) has a groove width greater than or equal to 80% of a groove width of the shoulder main groove (30).
  7. The pneumatic tire according to any one of claims 1 to 6, wherein all of the blocks arranged in the center region (50) and the shoulder regions (40) have rounded corners; and wherein a radius of curvature of each of the rounded corners is greater than or equal to 1.0 mm and less than or equal to 3.0 mm.
  8. The pneumatic tire (1) according to claim 1, wherein the area of the center block (51) is greater than or equal to 0.90 times and less than or equal to 0.95 times of the area of the largest block.
  9. The pneumatic tire (1) according to claim 1, wherein the middle block (52,53) comprises a first middle block (52) arranged on each side of the center block (51) in the tire axial direction and a second middle block (53) arranged on each side of the center block (51) in the tire circumferential direction.

Description

TECHNICAL FIELD The present invention relates to a pneumatic tire. BACKGROUND A pneumatic tire having a tread is disclosed in JP 2019-199206 A ('206 patent) in which the tread has a pair of shoulder main grooves continuously extending in a tire circumferential direction, a pair of crown main grooves continuously extending in the tire circumferential direction at positions located, in a tire axial direction, inward of the shoulder main grooves, and a middle land disposed between the crown main groove and the shoulder main groove. The '206 patent further discloses that the middle land includes a first middle block with a tread surface area of S1 and a second middle block with a tread surface area of S2, and a ratio of S1 / S2 is greater than or equal to 0.9 and less than or equal to 1.1. In recent years, there has been a demand for suppression of uneven wear and chipping of pneumatic tires during driving. In particular, suppression of uneven wear and chipping during driving is strongly demanded of off-road tires which are expected to run on irregular ground and thus receive great input force from road surfaces. JP 2003 054222 A describes a pneumatic tire that suppress eccentric wear between blocks while a pitch length of a block in the peripheral direction is changed. JP 2008 265501 A describes a pneumatic tire secured in lateral grip performance and improved in riding performance especially in a super low µ road surface, while exhibiting excellent traction performance. US 2021 039445 A1 describes a pneumatic tire that will make it possible to suppress occurrence of variation in rigidity at blocks. SUMMARY The present invention is defined by the independent claim. Preferred examples are defined in the dependent claims. In the pneumatic timer according to this invention, both uneven wear and chipping during driving can be suppressed. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows half of a cross sectional view of a pneumatic tire according to an example embodiment;FIG. 2 is a plan view showing a tread of the pneumatic tire according to the example embodiment;FIG. 3 is a plan view showing a tread of a pneumatic tire according to Experiment Example 2; andFIG. 4 is a diagram showing longitudinal stiffness of each block that is calculated through a simulation. DESCRIPTION OF EMBODIMENTS Hereinafter, an example embodiment of a pneumatic tire according to this disclosure will be explained in detail with reference to the drawings. The embodiment described below is merely presented by way of illustration. FIG. 1 shows half of a cross sectional view of a pneumatic tire 1 according to an example embodiment and illustrates an internal structure of the tire 1. As shown in FIG. 1, the pneumatic timer 1 includes a tread 10 which is a part that is brought into contact with the road surface, a pair of side walls 11 disposed on both sides of the tread 10, and a pair of beads 12 disposed inward of the side walls 11 in a tire radial direction. In addition, the pneumatic tire 1 further includes a carcass 13 configured to bridge between the pair of beads 12. The pneumatic tire 1 is designed to be adapted to off road use. The tread 10 includes a pair of shoulder main grooves 30 continuously extending in a tire circumferential direction. The tread 10 further includes both a pair of shoulder regions 40 which are respectively disposed outward of the shoulder main grooves 30 in a tire axial direction and delimited by a pair of ground contact edges E, and a center region 50 disposed between the pair of shoulder main grooves 30. As used herein, the ground contact edges E are defined as both ends, in the tire axial direction, of a region that is brought into contact with a flat road surface when a normal load is applied to an unused pneumatic tire 1 mounted on a normal rim and filled with air to a normal internal pressure. Here, the "normal rim" is a rim designated by tire standards, and is a "standard rim" according to JATMA and a "measuring rim" according to TRA and ETRTO. The "normal internal pressure" is the "maximum air pressure" according to JATMA, the maximum value shown in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" according to TRA, and the "inflation pressure" according to ETRTO. The "normal load" is the "maximum load performance" according to JATMA, the maximum value shown in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" according to TRA, and the "LOAD CAPACITY" according to ETRTO. As will be explained in detail below, a plurality of blocks having various shapes that differ from each other are arranged in the shoulder region 40 and the center region 50 of the tread 10. In a top view of the tread 10, an area of a largest block having the maximum area among areas of the blocks disposed in the center region 50 and the shoulder region 40 is less than or equal to 1.4 times of an area of a smallest block having the minimum area. When the area of the largest block is defined to be less than or equal