阅读说明：本技术 充气轮胎 (Pneumatic tire ) 是由 小原将明 于 2019-06-10 设计创作，主要内容包括：技术问题：防止横槽处的排水性及排泥性变差,并且抑制槽底处的裂纹的产生及生长。解决方案：在胎面部具备由沿轮胎周向延伸的多个主槽(7)、和与主槽(7)交叉且沿轮胎宽度方向延伸的多个横槽(8)形成的多个胎块(9)。横槽(8)具有在槽底形成有多个突出部(15)的增强区域(16)。在增强区域(16),在沿轮胎周向延伸的任意的线上配置有至少任意一个突出部(15)。(The technical problem is as follows: prevent deterioration of drainage and sludge discharge at the horizontal grooves and suppress generation and growth of cracks at the grooves. The solution is as follows: the tread portion is provided with a plurality of blocks (9) formed by a plurality of main grooves (7) extending in the tire circumferential direction and a plurality of lateral grooves (8) intersecting the main grooves (7) and extending in the tire width direction. The lateral groove (8) has a reinforcing region (16) in which a plurality of projections (15) are formed on the groove bottom. At least one of the protrusions (15) is arranged on any line extending in the tire circumferential direction in the reinforcing region (16).)

1. A pneumatic tire, wherein,

the tread portion is provided with a plurality of blocks formed by a plurality of main grooves extending along the tire circumferential direction and a plurality of transverse grooves intersecting the main grooves and extending along the tire width direction,

the lateral groove has a reinforcing region formed with a plurality of projections at a groove bottom,

at least one of the protrusions is disposed on an arbitrary line extending in the tire circumferential direction in the reinforcing region.

2. A pneumatic tire according to claim 1,

the reinforcing region is provided at a middle portion in the tire circumferential direction of a groove bottom of the lateral groove.

3. A pneumatic tire according to claim 1 or 2,

the groove bottom of the transverse groove is composed of a bottom surface between adjacent blocks along the circumferential direction of the tire and a curved surface connecting the side surface of each block and the bottom surface,

the protruding portion is disposed on the bottom surface.

4. A pneumatic tire according to any one of claims 1 to 3,

the reinforcing region is provided at a middle portion in the tire width direction of a groove bottom of the lateral groove.

5. A pneumatic tire according to any one of claims 1 to 4,

at least one of the protrusions is disposed on an arbitrary line extending in the tire width direction in the reinforcing region.

6. A pneumatic tire according to any one of claims 1 to 5,

the blocks dividing the transverse grooves are shoulder blocks.

7. A pneumatic tire according to claim 6,

the outer surface of the shoulder block is composed of two curved surfaces with different curvature radiuses on the meridian section of the tire,

the reinforcing region is located in a region that includes a boundary line between the two curved surfaces and extends in the tire circumferential direction.

8. A pneumatic tire according to any one of claims 1 to 7,

the protruding portion formed in the reinforcing region is configured by a bead extending in the tire width direction, and a plurality of protrusions located on both sides of the bead.

Technical Field

The present invention relates to a pneumatic tire.

Background

Conventionally, there is known a pneumatic tire in which a plurality of stone ejectors each having a button shape are provided in grooves formed in a tread (for example, see patent document 1).

However, in the above-described conventional pneumatic tire, the projections formed in the grooves are only stone ejectors for preventing small stones or the like from being fitted into the grooves. In the region where the stone ejector is formed, there is a line without the stone ejector when viewed in the tire circumferential direction. At this line, a distance (thickness) from the groove bottom to the belt as an internal structural member cannot be sufficiently secured, and cracks are likely to occur along the tire circumferential direction. Further, simply making the groove shallower and making the wall thickness thicker deteriorates drainage or sludge discharge.

Disclosure of Invention

Technical problem to be solved

The present invention has been made in an effort to provide a pneumatic tire that can prevent deterioration of drainage and mud drainage at a lateral groove and can suppress generation and growth of cracks at a groove bottom.

(II) technical scheme

The present invention provides a pneumatic tire in which a tread portion includes a plurality of blocks each formed of a plurality of main grooves extending in a tire circumferential direction and a plurality of lateral grooves intersecting the main grooves and extending in a tire width direction, the lateral grooves each have a reinforcing region in which a plurality of protrusions are formed at a groove bottom, and at least one of the protrusions is arranged on an arbitrary line extending in the tire circumferential direction in the reinforcing region.

According to this structure, with the plurality of protrusions provided in the reinforcing region, the distance from the groove bottom to the belt can be ensured even on an arbitrary line extending in the tire circumferential direction. Therefore, the generation and growth of cracks in the tire circumferential direction can be suppressed. Further, since the projection is formed of a plurality of projections, the drainage property and the sludge discharge property are not deteriorated.

Preferably, the reinforcing region is provided at a middle portion in the tire circumferential direction of the groove bottom of the lateral groove.

According to this structure, as compared with the structure provided over the entire area, deterioration of drainage and mud drainage can be minimized, and the effect of preventing frictional contact generated when the blocks divided in the circumferential direction are grounded can be maintained at the lateral grooves, so that the occurrence of cracks can be effectively suppressed.

Preferably, a groove bottom of the lateral groove is formed by a bottom surface between blocks adjacent in the tire circumferential direction and a curved surface connecting a side surface of the block and the bottom surface, and the protruding portion is provided on the bottom surface.

According to this structure, the tire can be prevented from being cracked more effectively without being affected by the deformation of the tire block during the grounding.

Preferably, the reinforcing region is provided at a middle portion in the tire width direction of a groove bottom of the lateral groove.

According to this structure, the reinforcement function at the tank bottom can be improved, and desired drainage and sludge discharge can be ensured.

Preferably, at least any one of the protrusions is arranged on any line extending in the tire width direction in the reinforcing region.

According to this structure, the generation and growth of cracks in the tire width direction can be suppressed.

Preferably, the blocks dividing said transverse grooves are shoulder blocks.

According to this configuration, it is possible to effectively prevent the occurrence of cracks in the lateral grooves formed between the shoulder blocks having the largest ground contact surface deformation amount.

Preferably, the outer surface of the shoulder block is formed of two curved surfaces having different radii of curvature in a tire meridian cross section, and the reinforcing region is located in a region extending in the tire circumferential direction and including a boundary line between the two curved surfaces.

According to this structure, it is possible to effectively prevent the occurrence of cracks in the lateral grooves corresponding to the portions of the shoulder blocks where the amount of deformation is the greatest.

Preferably, the protruding portion formed in the reinforcing region is constituted by a bead extending in the tire width direction, and a plurality of protrusions located on both sides of the bead.

According to this configuration, the mud drainage performance can be ensured by the bead extending in the tire width direction, the rubber thickness of the groove bottom can be ensured by the protrusions arranged on both sides of the bead from the belt, and the drainage performance at the time of tire wear can be maintained by forming a plurality of protrusions.

(III) advantageous effects

According to the present invention, the plurality of protrusions provided in the reinforcing region can sufficiently secure the distance between the groove bottom of the lateral groove and the belt as the internal structural member, thereby suppressing the occurrence and growth of cracks. Further, since the plurality of projections are provided, desired drainage and sludge discharge properties can be ensured.

Drawings

Fig. 1 is a tire meridian partial sectional view of the pneumatic tire of the present embodiment.

Fig. 2 is a developed view showing a part of a tread portion of the pneumatic tire shown in fig. 1.

Fig. 3 is a perspective view of the shoulder blocks and the shoulder transverse grooves shown in fig. 1.

FIG. 4 is a cross-sectional view of the shoulder cross-groove shown in FIG. 1.

Fig. 5 is a top view of a protrusion according to another embodiment.

Fig. 6 is a top view of a protrusion according to another embodiment.

Fig. 7 is a top view of a protrusion according to another embodiment.

Fig. 8 is a top view of a protrusion according to another embodiment.

Fig. 9 is a perspective view of a protrusion according to another embodiment.

Description of the reference numerals

1-a bead core; 2-a carcass ply; 3-bead filler; 4-an inner liner layer; 5-belting; 6-a tread portion; 7-a main tank; 8-a transverse groove; 9-a block; 10-a central block; 11-shoulder blocks; 12-a first curved surface; 13-a second curved surface; 14-shoulder transverse grooves; 15-protrusions (projections); 16-an enhancement region; 17-protruding strip (protrusion).

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. The following description is merely exemplary in nature and is not intended to limit the present invention, its applications, or uses. The drawings are schematic, and the ratio of the dimensions and the like are different from those in reality.

Fig. 1 is a radial semi-sectional view of the pneumatic tire of the present embodiment. In this pneumatic tire, a carcass ply 2 is bridged between a pair of bead cores 1. Both ends of the carcass ply 2 are wound around the bead core 1 and the bead filler 3 provided in contact with the bead core 1. An inner liner 4 is provided inside the carcass ply 2. A plurality of belts 5 are wound around the outer periphery of the carcass ply 2. The outer periphery of the belt 5 is a tread portion 6.

Fig. 2 is a developed view showing a part of the tread portion 6 of the pneumatic tire of the present embodiment. In the tread portion 6, a plurality of blocks 9 are formed by a plurality of main grooves 7 extending in the tire circumferential direction and a plurality of lateral grooves 8 intersecting the main grooves 7 and extending in the tire width direction. The main groove 7 is formed in a zigzag shape, but may be formed in various known forms such as a straight line shape and a curved shape. Therefore, in the case of merely being described as "the tire circumferential direction", it means substantially the tire circumferential direction, and can be understood as a broad concept including the extending direction of these various forms. The lateral grooves 8 may also take various forms as in the main grooves 7, and when simply referred to as "the tire width direction", they are substantially in the tire width direction, and can be understood as a broad concept including the extending direction of these various forms. The main grooves 7 and the lateral grooves 8 have the same depth.

The block 9 has two rows of a plurality of center blocks 10 arranged along the tire circumferential direction along the tire equatorial plane CL. The block 9 includes a plurality of shoulder blocks 11 disposed along the tire circumferential direction on the side (both sides in the tire width direction) of each center block 10.

The outer surface of the shoulder block 11 is constituted by a first curved surface 12 and a second curved surface 13, wherein the radius of curvature of the outer surface of the first curved surface 12 in a tire meridian semi-sectional view shown in fig. 1 is R1, and the radius of curvature of the second curved surface 13 is R2. As shown in fig. 2 and 3, a boundary line BL between the first curved surface 12 and the second curved surface 13 extends in the tire circumferential direction. The predetermined regions on both sides of the boundary line BL are portions where the deformation amount of the shoulder blocks 11 is the largest.

As shown in fig. 4, the lateral grooves 8 (shoulder lateral grooves 14) formed between the shoulder blocks 11 adjacent in the tire circumferential direction are divided by the side surfaces 11a of the shoulder blocks 11, the bottom surfaces 11b formed between the shoulder blocks 11, and the curved surfaces 11c connecting the side surfaces 11a and the bottom surfaces 11 b. Here, the groove bottom of the shoulder lateral groove 14 is composed of a bottom surface 11b and a curved surface 11 c. The groove depth GD of the shoulder lateral groove 14, that is, the distance in the tire radial direction from the outer surface to the bottom surface of the shoulder block 11 was set to 15 mm. The groove width of the shoulder transverse groove 14, that is, the interval between the side surfaces of the shoulder blocks 11 adjacent in the tire circumferential direction, is set such that the side surfaces have an upper end WL1 of 25mm and a lower end curved surface has an upper end WL2 of 17 mm.

As shown in fig. 3, a plurality of protrusions 15 are formed as projections on the bottom surface of the shoulder transverse groove 14, and form a reinforcing region 16. The reinforcing region 16 occupies the middle portion of the shoulder transverse groove 14 in the tire width direction. Here, both side regions of the shoulder transverse groove 14 centered on the extension line of the boundary line BL are reinforcement regions 16. The reinforcing region 16 is a portion where bending stress is repeatedly applied when the shoulder blocks 11 contact and leave the ground. By making the region including the boundary line BL the reinforcing region 16, the region having the largest deformation amount at the time of grounding can be reinforced.

As shown in fig. 2, the reinforcing region 16 is set such that the ratio EL/SL of the length SL of the shoulder lateral groove 14 in the tire width direction to the length EL of the reinforcing region 16 is 15% to 65%, preferably 30% to 45%. The length SL of the shoulder lateral groove 14 indicates the shortest distance on the tire meridian cross section between the tire width direction inner end of the shoulder block 11 and the ground contact end position CE of the shoulder block 11. The ratio NEL/SL of the length NEL of the non-reinforced region in the tire width direction to the length SL of the shoulder lateral groove 14 is set to 20% to 40%, preferably 30% to 35%. If EL/SL < 15%, the reinforcement is insufficient, and if 65% < EL/SL, the drainage and sludge discharge may be poor.

In addition, the reinforcing region 16 is located at a middle portion in the tire circumferential direction of the shoulder lateral groove 14. Here, a reinforcing region 16 is provided on the bottom surface of the groove bottom of the shoulder transverse groove 14 excluding the curved surface. By not forming the protrusions 15 on the curved surface, the problem of easy occurrence of cracks is avoided.

The projection 15 is formed in a truncated conical shape whose cross-sectional area gradually decreases from the bottom surface toward the outer side in the tire radial direction. Here, each protrusion 15 is designed such that: the diameter of the bottom surface is 3mm, the diameter of the upper end surface is 2mm, and the height is 2 mm. As shown in fig. 5, the protrusions 15 are staggered. In detail, the protrusions 15 are arranged in the reinforcing region 16 such that at least the bottom surface portions thereof are located on an arbitrary line extending in the tire circumferential direction. The protrusions 15 are arranged so as to be positioned on an arbitrary line extending in the tire width direction in the reinforcing region 16. Further, the protrusion 15 is designed to occupy 50% to 70% of the area of the reinforcing region 16 when viewed in plan. If the content is less than 50%, the reinforcing function for preventing the occurrence of cracks is insufficient, and if the content exceeds 70%, the desired drainage property and sludge discharge property cannot be secured.

In the pneumatic tire provided with the reinforced region 16 described above, the following effects can be achieved.

By arranging the projections 15 in a staggered manner, the rigidity as a whole can be increased in a balanced manner. Further, although stress concentrates on the reinforcing region 16 when the shoulder blocks 11 contact and leave the ground, the projections 15 can suppress the occurrence of cracks. Even if a crack occurs, it is inevitable that the growth of the crack in the tire circumferential direction or the tire width direction can be suppressed by the arbitrary protrusion 15.

Since the projections 15 are provided in plurality, the original depth of the shoulder transverse groove can be secured in the portion where the projections 15 are not formed. Therefore, although the reinforced area 16 is provided, the drainage property and the mud discharge property are not deteriorated even when the vehicle travels on a wet road surface or a rough road surface.

When the green tire is vulcanized, the rubber is pushed open at the portion serving as the shoulder transverse groove 14. In order to ensure a desired wall thickness between the groove bottom and the belt 5, the amount of rubber needs to be increased in this portion in advance. However, if the amount of rubber is increased, the belt 5 is locally moved inward by the rubber pushed open at the time of vulcanization molding, and the like, and the rigidity of the tire in the rotational direction is varied. Further, the thickness of the shoulder block 11 is increased from the ideal value, which affects durability and deteriorates uniformity of the tire. By forming the plurality of protrusions 15, the amount of rubber pushed open can be reduced, and the occurrence of such a problem can be prevented.

The present invention is not limited to the configuration described in the above embodiment, and various modifications are possible.

Although the projections 15 are formed in a truncated conical shape in the above embodiment, various shapes such as a cylindrical shape, a rectangular parallelepiped shape, a cubic shape, and a hemispherical shape may be adopted.

Although the example of the protrusion 15 is shown as a protruding portion in the above embodiment, a structure having a certain length, a structure having a different shape in a plan view, or the like may be included. Other examples of projections are shown in fig. 6 to 9.

Fig. 6 shows an example in which the protruding portion is formed of a plurality of ridges. The ribs 17 are arranged to be inclined at 45 ° with respect to the tire width direction in which the shoulder lateral grooves 14 extend. The center and both sides in the width direction of the shoulder transverse groove 14 have different inclination directions of the ridge 17. These beads 17 are arranged so as to be positioned on any line when viewed in any one of the tire circumferential direction and the tire width direction, similarly to the above-described protrusions 15.

Fig. 7 shows an example in which the protrusion portion is formed by the protrusion 15 having a triangular shape in a plan view. The protrusions 15 are arranged in two rows in the shoulder transverse groove, and are arranged in each row so that the positions of the protrusions 15 are shifted by one pitch, and the directions are opposite. In this example, the projections 15 are arranged so as to be positioned on any line when viewed in any one of the tire circumferential direction and the tire width direction.

Fig. 8 shows an example in which the protrusion portion is formed by a protrusion 15 that is bent so as to open in a C-shape in one direction. The protrusions 15 are arranged in three rows in the shoulder transverse groove, and the positions of the opening sides are opposite in the center portion and the both side portions. The projections of the central portion are open to the left in the figure, and the projections of both side portions (up and down in the figure) are open to the right in the figure.

Fig. 9 shows an example in which the protrusion portion is constituted by the ridge 17 and the protrusion 15. The rib 17 extends in the tire width direction at the widthwise central portion of the shoulder lateral groove 14, and divides the shoulder lateral groove 14 into two parts in the tire circumferential direction. The projections 15 are disposed on both sides of the ridge 17, and are formed in plural at predetermined intervals in the tire width direction.

According to the examples of fig. 6 to 9, the growth of cracks occurring in the circumferential direction can also be prevented by the protrusions 15 or the ridges 17, and the growth of cracks in the groove depth direction can also be suppressed because the crack length is shortened.

In the above embodiment, the shape and size of each protruding portion are the same, but either one or both of them may be different.

Although the reinforcing regions 16 are formed in the shoulder lateral grooves 14 in the above embodiment, the reinforcing regions may be formed in the central lateral grooves formed between the center blocks 10 adjacent in the tire circumferential direction. In addition, if the tire has an intermediate block between the center block 10 and the shoulder block 11, a reinforcing region can be formed in an intermediate lateral groove formed between adjacent intermediate blocks in the tire circumferential direction. However, the reinforcing region 16 is most effective when applied to the shoulder transverse groove 14 of the shoulder block 11 having the largest deformation amount when the tread portion 6 contacts and separates from the ground.