JP7035693B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire suitable as an all-season tire, and more particularly to a pneumatic tire capable of suppressing the generation of pattern noise and improving snow performance while suppressing a decrease in block rigidity. ..

All-season tires are required to exhibit excellent snow performance during snowfall. On the other hand, in the conventional all-season tire, by providing a plurality of lug grooves having a bent shape in the land part of the tread part, the edge component due to the groove acts in all directions and the land part of the tread part is formed. The snow performance is improved by providing a plurality of treads in the tire (see, for example, Patent Document 1).

However, when a plurality of lug grooves having a bent shape are provided in the tread portion, there is a problem that the block rigidity is lowered. Further, depending on the arrangement of the sipes provided in the tread portion, the decrease in block rigidity may be promoted. Further, there is a problem that pattern noise is likely to occur due to the decrease in block rigidity. Further, when the block rigidity is lowered, the wear resistance is deteriorated and the steering stability performance on a dry road surface tends to be deteriorated.

Japanese Unexamined Patent Publication No. 2014-205410

An object of the present invention is to provide a pneumatic tire capable of suppressing the generation of pattern noise and improving the snow performance while suppressing the decrease in block rigidity.

The pneumatic tire of the present invention for achieving the above object has a tread portion extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and these sidewall portions. It is provided with a pair of bead portions arranged inside in the tire radial direction, and the tread portion is provided with four main grooves including a pair of inner main grooves and a pair of outer main grooves extending in the tire circumferential direction. In a pneumatic tire in which a pair of intermediate land portions located outside the center land portion and the center land portion and a pair of shoulder land portions located outside the intermediate land portion are separated by a groove, the center land portion and the center land portion and the center land portion are separated. A plurality of sipes are provided in each of the shoulder land portions at intervals in the tire circumferential direction, and the intermediate land portion intersects with a plurality of lug grooves having sharply bent portions with respect to these lug grooves. A plurality of treads extending in the direction are provided, and each lug groove has one end opened in the outer main groove while the other end is terminated in the intermediate land portion and the tire circumferential direction. The tires are arranged so as not to overlap each other, and the groove width of the sipe in the intermediate land portion is narrower than the groove width of each sipe in the center land portion and the shoulder land portion.

In the present invention, a plurality of sipes are provided at intervals in the tire circumferential direction in each of the center land portion and the shoulder land portion, and a plurality of lug grooves having sharp bending portions and these lugs are provided in the intermediate land portion. A plurality of sipes extending in the direction intersecting the groove are provided, and each lug groove is provided with one end opening into the outer main groove while the other end terminating in the intermediate land. Since the tires are arranged so as not to overlap each other in the circumferential direction of the tire, it is possible to improve the snow performance (particularly, the steering stability performance on a snowy road surface) while suppressing a decrease in block rigidity. In addition, the block rigidity is locally reduced due to the crossing of the sipe with the lug groove in the intermediate land area, but the groove width of the sipe in the intermediate land area is larger than the groove width of each sipe in the center land area and the shoulder land area. Since it is set narrowly, it is possible to suppress a decrease in block rigidity in the intermediate land area and suppress the generation of pattern noise. Further, since the decrease in block rigidity can be suppressed, the wear resistance can be improved and the steering stability performance on a dry road surface can be improved.

In the present invention, it is preferable that the orientation of the center land portion and the shoulder land portion with respect to the tire width direction is opposite to that of the intermediate land portion. As a result, the generation of pattern noise can be effectively suppressed.

In the present invention, it is preferable that the width W1 of the center land portion, the width W2 of the intermediate land portion, and the width W3 in the ground contact region of the shoulder land portion satisfy the relationship of W1 <W2 <W3. As a result, the width of the intermediate land portion can be secured relatively wide, and the steering stability performance on a dry road surface can be effectively improved.

In the present invention, it is preferable that a plurality of lug grooves are provided in the shoulder land portion at intervals in the tire circumferential direction, and the total number of lug grooves and sipes in the shoulder land portion is larger than the number of sipes in the intermediate land portion. .. As a result, the number of grooves in the shoulder land portion can be relatively increased, and the generation of pattern noise can be effectively suppressed while suppressing the decrease in block rigidity in the intermediate land portion.

It is a cross-sectional view of the meridian which shows the pneumatic tire which comprises embodiment of this invention. It is a top view which shows an example of the tread part of the pneumatic tire which comprises embodiment of this invention.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 and 2 show a pneumatic tire according to an embodiment of the present invention. In FIG. 2, Tc indicates the tire circumferential direction, and Tw indicates the tire width direction.

As shown in FIG. 1, the pneumatic tire according to the embodiment of the present invention has a tread portion 1 extending in the tire circumferential direction and forming an annular shape, and a pair of sidewall portions arranged on both sides of the tread portion 1. It includes 2, 2 and a pair of bead portions 3, 3 arranged inside the sidewall portions 2 in the tire radial direction.

A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the radial direction of the tire, and is folded back from the inside to the outside of the tire around the bead core 5 arranged in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross section is arranged on the outer periphery of the bead core 5.

On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to intersect each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set to, for example, in the range of 10 ° to 40 °. As the reinforcing cord of the belt layer 7, a steel cord is preferably used. At least one belt cover layer 8 having reinforcing cords arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction is arranged on the outer peripheral side of the belt layer 7 for the purpose of improving high-speed durability. There is. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

The above-mentioned tire internal structure shows a typical example of a pneumatic tire, but is not limited thereto.

As shown in FIG. 2, the tread portion 1 is formed with four main grooves 9 extending in the tire circumferential direction. The main groove 9 includes a pair of inner main grooves 9A and 9A located on both sides of the tire center line CL and a pair of outer main grooves 9B and 9B located on the outermost side in the tire width direction. The land portion 10 is divided into the tread portion 1 by these four main grooves 9. The land portion 10 includes a center land portion 10A located on the tire center line CL, a pair of intermediate land portions 10B and 10B located outside the center land portion 10A in the tire width direction, and each intermediate land portion 10B in the tire width direction. It includes a pair of shoulder land portions 10C and 10C located on the outside.

A plurality of sipes 11A and a plurality of fine grooves 31 inclined in the same direction with respect to the tire width direction are formed in the center land portion 10A at intervals in the tire circumferential direction. The sipe 11A has one end communicating with the inner main groove 9A and the other end communicating with the narrow groove 31. That is, the sipe 11A is an open sipe. On the other hand, the narrow groove 31 is a groove having a wider groove width than the sipe 11A. One end of the narrow groove 31 communicates with the inner main groove 9A, and the other end communicates with the sipe 11A. Such sipes 11A and fine grooves 31 are alternately arranged in the tire circumferential direction, and the fine grooves 31 are arranged in a staggered manner in the tire circumferential direction as a whole of the center land portion 10A.

A plurality of lug grooves 21 inclined in the same direction with respect to the tire width direction are formed in the intermediate land portion 10B at intervals in the tire circumferential direction. In these lug grooves 21, one end 21a opens into the outer main groove 9B, while the other end 21b terminates in the intermediate land portion 10B. Each of the lug grooves 21 is arranged so as not to overlap each other in the tire circumferential direction. Further, the lug groove 21 has a bent portion 22 formed in an acute angle shape at an intermediate position between one end portion 21a and the other end portion 21b.

Further, in the intermediate land portion 10B, a plurality of sipes 11B extending in a direction intersecting the lug groove 21 are formed at intervals in the tire circumferential direction. These sipes 11B have a structure divided into a plurality of portions by penetrating the lug groove 21, but the divided portions in the same sipe 11B are arranged on the same straight line with each other. As a whole, each of the sipes 11B has one end communicating with the inner main groove 9A and the other end communicating with the outer main groove 9B. That is, the sipe 11B is an open sipe.

A plurality of lug grooves 24 inclined in the same direction with respect to the tire width direction are formed in the shoulder land portion 10C at intervals in the tire circumferential direction. These lug grooves 24 are not in communication with the outer main groove 9B. Further, on the shoulder land portion 10C, a plurality of sipes 11C inclined in the same direction with respect to the tire width direction are formed at intervals in the tire circumferential direction. Both ends of these sipes 11C are terminated within the shoulder land portion 10C. That is, the sipe 11C is a closed sipe.

In the pneumatic tire, the groove width of the sipe 11A of the center land portion 10A is t1, the groove width of the sipe 11B of the intermediate land portion 10B is t2, and the groove width of the sipe 11C of the shoulder land portion 10C is t3. At this time, the groove width t2 of the sipe 11B of the intermediate land portion 10B is narrower than the groove width t1 of the sipe 11A of the center land portion 10A and the groove width t3 of the sipe 11C of the shoulder land portion 10C. At that time, the groove width t1 of the sipe 11A of the center land portion 10A and the groove width t3 of the sipe 11C of the shoulder land portion 10C may be set to the same groove width or different groove widths. Is also good. In particular, the groove width t2 of the sipe 11B of the intermediate land portion 10B is set to 0.5 to 0.8 times the groove width t1 of the sipe 11A of the center land portion 10A and the groove width t3 of the sipe 11C of the shoulder land portion 10C. Is preferable. The sipe 11 is a groove having a groove width of 1.5 mm or less.

In the above-mentioned pneumatic tire, a plurality of sipes 11A and 11C are provided at intervals in the tire circumferential direction on each of the center land portion 10A and the shoulder land portion 10C, and a sharp bending portion 22 is provided on the intermediate land portion 10B. A plurality of lug grooves 21 having a plurality of lug grooves 21 and a plurality of sipes 11B extending in a direction intersecting the lug grooves 21 are provided, and one end portion 21a of each lug groove 21 is formed in the outer main groove 9B. While opening, the other end 21b is terminated in the intermediate land portion 10B and is arranged so as not to overlap each other in the tire circumferential direction, so that snow performance (particularly on snow) while suppressing a decrease in block rigidity is suppressed. It is possible to improve steering stability performance on the road surface). Further, the block rigidity is locally reduced by the sipe 11B penetrating the lug groove 21 in the intermediate land portion 10B, but the groove width t2 of the sipe 11B in the intermediate land portion 10B is the groove width of the sipe 11A in the center land portion 10A. Since the groove width t3 of the sipe 11C of the t1 and the shoulder land portion 10C is set to be narrower, it is possible to suppress a decrease in block rigidity in the intermediate land portion 10B and suppress the generation of pattern noise. Further, since the decrease in block rigidity can be suppressed, the wear resistance can be improved and the steering stability performance on a dry road surface can be improved.

In the pneumatic tire, as shown in FIG. 2, the orientation of the sipe 11A of the center land portion 10A and the sipe 11C of the shoulder land portion 10C with respect to the tire width direction is opposite to that of the sipe 11B of the intermediate land portion 10B. By configuring the sipes 11A to 11C of the land portions 10A to 10C in this way, the generation of pattern noise can be effectively suppressed. Here, if the directions of the sipes 11A to 11C of the land portions 10A to 10C with respect to the tire width direction are the same, they tend to overlap with the ground contact front end line, and the pattern noise tends to worsen.

Further, the width W1 of the center land portion 10A, the width W2 of the intermediate land portion 10B, and the width W3 in the ground contact region of the shoulder land portion 10C are configured to satisfy the relationship of W1 <W2 <W3. By setting the widths W1 to W3 of each land portion 10A to 10C so as to satisfy such a relationship, the width W2 of the intermediate land portion 10B can be secured relatively wide, and the steering stability performance on a dry road surface can be improved. It can be improved effectively. Here, if the width W3 of the shoulder land portion 10C is too narrow, the steering stability performance and the braking performance on a dry road surface tend to deteriorate.

The width W3 of the shoulder land portion 10C in the ground contact region is specifically the width from the end portion of the shoulder land portion 10C on the outer main groove 9B side to the ground contact end E. The ground contact end E is the outermost position in the tire width direction of the ground contact region. The ground contact area is a tire that is filled with air pressure corresponding to the maximum load capacity specified for each tire according to the tire-based standards (JATMA, TRA, ETRTO, etc.) and placed vertically on a flat plate in a stationary state. It is a region in the tire width direction corresponding to the maximum linear distance in the tire width direction on the ground contact surface formed on the flat plate when a load corresponding to 80% of the load capacity is applied.

Further, the total number N2 of the lug groove 24 and the sipes 11C in the shoulder land portion 10C is formed to be larger than the number N1 of the sipes 11B in the intermediate land portion 10B. In particular, the total number N2 of the lug groove 24 and the sipes 11C in the shoulder land portion 10C is preferably set to 1.1 to 1.3 times the number N1 of the sipes 11B in the intermediate land portion 10B. With this configuration, the number of grooves in the shoulder land portion 10C can be relatively increased, and the generation of pattern noise can be effectively suppressed while suppressing the decrease in block rigidity in the intermediate land portion 10B. Here, when the total number N2 of the lug groove 24 and the sipes 11C in the shoulder land portion 10C and the number N1 of the sipes 11B in the intermediate land portion 10B are set to the same number, pattern noise tends to be remarkably generated. On the other hand, if the number N1 of the sipes 11B in the intermediate land portion 10B is larger than the total number N2 of the lug grooves 24 and the sipes 11C in the shoulder land portion 10C, it is not preferable because it leads to a decrease in block rigidity. The number N1 of the sipes 11B in the intermediate land portion 10B and the total number N2 of the lug grooves 24 and the sipes 11C in the shoulder land portion 10C are the number of target grooves included in the entire circumference of the tire in each land portion.

With a tire size of 225 / 50R18, a tread portion extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and these sidewall portions are arranged inside the tire radial direction. It is provided with a pair of bead portions, and the tread portion is provided with four main grooves including a pair of inner main grooves and a pair of outer main grooves extending in the tire circumferential direction, and these main grooves provide a center land portion and its center land. In a pneumatic tire in which a pair of intermediate land portions located outside the portion and a pair of shoulder land portions located outside the intermediate land portion are partitioned, each of the center land portion and the shoulder land portion is in the tire width direction. A plurality of sipe inclined with respect to the tire is provided, and a plurality of lug grooves having sharp bends and a plurality of sipe extending in a direction intersecting the lug grooves are provided in the intermediate land portion. Each lug groove is arranged so that one end opens into the outer main groove while the other end ends in the intermediate land and is not overlapped with each other in the tire circumferential direction. The groove width of the tire is narrower than the groove width of each of the center land and shoulder sipe, the groove width t2 of the intermediate sipe, the groove width t1 of the center sipe and the groove width of the shoulder sipe. t3, the inclination direction of the sipe of each land area with respect to the tire width direction, the magnitude relationship of the widths W1, W2, W3 of each land area, the total number of lug grooves and sipe in the shoulder land area with respect to the number of sipe in the intermediate land area N1. The tires of the conventional example and Examples 1 to 4 in which the ratio (N2 / N1) of the tires was set as shown in Table 1 were manufactured.

For these test tires, a sensory evaluation of steering stability performance on snowy road surface, pattern noise and steering stability performance on dry road surface was carried out by a test driver, and the results are also shown in Table 1.

Sensory evaluation of steering stability performance on snowy roads was carried out by assembling each test tire to a rim size 18 × 7J wheel and mounting it on a front-wheel drive vehicle. The evaluation results are shown by evaluation values on a scale of 10. The larger this evaluation value is, the better the steering stability performance on the snowy road surface is.

Sensory evaluation of pattern noise was performed by assembling each test tire to a rim size 18 × 7J wheel and mounting it on a front-wheel drive vehicle. The evaluation results are shown by evaluation values on a scale of 10. The larger this evaluation value is, the better the effect of suppressing the generation of pattern noise is.

The sensory evaluation of the steering stability performance on a dry road surface was carried out by assembling each test tire to a rim size 18 × 7J wheel and mounting it on a front-wheel drive vehicle. The evaluation results are shown by evaluation values on a scale of 10. The larger this evaluation value is, the better the steering stability performance on a dry road surface is.

As can be seen from Table 1, the tires of Examples 1 to 4 have improved steering stability performance on a snowy road surface, pattern noise, and steering stability performance on a dry road surface in a well-balanced manner as compared with the tires of the conventional example.

1 Tread part 2 Side wall part 3 Bead part 9 Main groove 9A Inner main groove 9B Outer main groove 10 Land part 10A Center land part 10B Intermediate land part 10C Shoulder land part 11A, 11B, 11C Sipe 21 Rug groove 22 Bending part t1, t2, t3 Groove width CL Tire center line E Grounding end

Claims (4)

A tread portion extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged inside the tire radial direction of these sidewall portions. The tread portion is provided with four main grooves including a pair of inner main grooves and a pair of outer main grooves extending in the tire circumferential direction, and these main grooves are located on the center land portion and outside the center land portion. In a pneumatic tire in which a pair of intermediate treads and a pair of shoulder treads located outside the intermediate treads are separated.
A plurality of sipes are provided in each of the center land portion and the shoulder land portion at intervals in the tire circumferential direction, and a plurality of lug grooves having sharply bent portions and these lug grooves are provided in the intermediate land portion. A plurality of sipes extending in intersecting directions with respect to the lug groove are provided, one end of which opens into the outer main groove and the other end of which terminates within the intermediate land portion. The tires are arranged so as not to overlap each other in the circumferential direction of the tire, and the groove width of the sipes in the intermediate land portion is narrower than the groove widths of the sipes in the center land portion and the shoulder land portion. tire. The pneumatic tire according to claim 1, wherein the direction of the sipe of the center land portion and the shoulder land portion with respect to the tire width direction is opposite to that of the sipe of the intermediate land portion. According to claim 1 or 2, the width W1 of the center land portion, the width W2 of the intermediate land portion, and the width W3 of the shoulder land portion in the ground contact region satisfy the relationship of W1 <W2 <W3. Pneumatic tires listed. A plurality of lug grooves are provided in the shoulder land portion at intervals in the tire circumferential direction, and the total number of lug grooves and sipes in the shoulder land portion is larger than the number of sipes in the intermediate land portion. The pneumatic tire according to any one of claims 1 to 3.

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