JP5523358B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which a plurality of land portions defined by a plurality of main grooves extending along a tire circumferential direction are provided on a tread surface.

  Of the multiple land portions provided on the tread surface, the land portion (shoulder land portion) located on the outermost side in the tire width direction tends to increase the load during cornering, so that the steering stability performance on dry road surfaces is improved. The effect is great. Such a phenomenon is particularly remarkable in a tire mounted on a minivan or a one-box vehicle having a heavy vehicle weight and a high center of gravity, and it is desired to take effective measures.

  By the way, when a shoulder land part is comprised by a some block (for example, following patent document 1), or when a lug groove is set and a shoulder land part is formed in a block shape (for example, following patent documents 2-5) Since the rigidity in the front-rear direction of the tire at the shoulder land portion decreases, the steering stability performance tends to decrease. On the other hand, when the shoulder land portion is constituted by ribs extending continuously in the tire circumferential direction, such a rigidity reduction can be suppressed, and the steering stability performance excellent in the ratio can be exhibited.

  However, as a result of repeated research by the present inventors, it has been found that the grounding property (uniformity of the grounding) is likely to be lowered as the longitudinal rigidity is increased simply by configuring the shoulder land portion with ribs. . And if the ground contact property of the shoulder land portion is lowered, it is strung locally during cornering traveling, and the whole cannot contribute, so it has been found that it is possible to improve the steering stability performance by improving this. Thus, in order to improve the steering stability performance, it is important to increase the ground contact property by appropriately reducing the longitudinal rigidity while maintaining the rigidity of the shoulder land portion in the longitudinal direction of the tire.

  Patent Document 6 listed below describes a pneumatic tire in which a plurality of grooves extending in the tire radial direction are arranged in the buttress portion in the tire circumferential direction. However, in this tire, since the groove of the buttress portion extends in the tire radial direction, the longitudinal rigidity is not sufficiently lowered. In addition, depending on the presence or absence of a groove, a difference in the level of ground pressure tends to occur near the grounding end, and the grounding property tends to deteriorate. In the first place, this groove is intended to cool the buttress part, and does not suggest a solution for a structure for appropriately reducing the longitudinal rigidity while maintaining the rigidity of the shoulder land part in the longitudinal direction of the tire.

Japanese Patent Application Laid-Open No. 2007-075532 JP 2008-105460 A JP 2008-273451 A JP 2009-0667180 A JP 2009-292252 A JP 2010-133203 A

  The present invention has been made in view of the above circumstances, and its purpose is to maintain the rigidity of the shoulder land portion in the front-rear direction of the tire while appropriately reducing the longitudinal rigidity to improve the steering stability performance. To provide tires.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention is provided with a plurality of land portions partitioned by a plurality of main grooves extending along the tire circumferential direction on the tread surface, and is located on the outermost side in the tire width direction. However, in the pneumatic tire constituted by shoulder ribs extending continuously in the tire circumferential direction, the shoulder ribs are defined as inner ribs on the inner side in the tire width direction and outer ribs on the outer side in the tire width direction with respect to the ground contact end. A groove area in the shoulder rib is larger in the outer rib than in the inner rib, and a pattern including a groove or a sipe is repeatedly formed in the tire circumferential direction on the inner rib. Longer in the tire circumferential direction than the repeated pitch length of the pattern on the ribs, both ends are closed in the outer rib and extend obliquely with respect to the tire circumferential direction, and are arranged in the tire circumferential direction. A plurality of inclined grooves and a short groove interposed between the inclined grooves, shorter in the tire circumferential direction than the inclined grooves, and closed at both ends within the outer rib are formed. .

  In this pneumatic tire, the land portion (shoulder land portion) located on the outermost side in the tire width direction is configured by a shoulder rib, and the groove area of the shoulder rib is larger at the outer rib than at the inner rib. Good rigidity can be secured in the anteroposterior direction of the land. Nevertheless, the longitudinal rigidity of the shoulder land portion is reduced by forming the long inclined groove in the tire circumferential direction on the outer rib. In addition, a short groove is interposed between the inclined grooves, and both end portions thereof are closed in the outer rib, so that an excessive decrease in the longitudinal rigidity can be prevented. As a result, in the pneumatic tire according to the present invention, while maintaining the rigidity of the shoulder land portion in the tire front-rear direction, the longitudinal rigidity can be appropriately lowered to improve the steering stability performance.

  In the present invention, it is preferable that the length of the inclined groove in the tire circumferential direction is 1.5 times or more of the repeated pitch length of the pattern on the inner rib. According to such a configuration, it is possible to satisfactorily secure the length of the inclined groove in the tire circumferential direction and effectively reduce the longitudinal rigidity of the shoulder land portion.

  In the present invention, the inclined grooves arranged in the tire circumferential direction are arranged so as not to overlap in the tire width direction, and both end portions of the short groove in the tire circumferential direction are respectively the front and rear inclined grooves in the tire circumferential direction. Those arranged at positions overlapping in the tire width direction are preferable. According to such a configuration, the inclined grooves and the short grooves can be arranged in a well-balanced manner in the tire circumferential direction, and the longitudinal rigidity of the shoulder land portion can be appropriately reduced.

The expanded view which shows an example of the tread surface of the pneumatic tire which concerns on this invention An enlarged view showing a part of the tread surface of FIG. Tire meridian cross-sectional view showing the periphery of the shoulder rib of the pneumatic tire (A) Enlarged view showing shoulder ribs in Comparative Example 1 and (b) Comparative Example 2

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The tread surface Tr of the pneumatic tire shown in FIG. 1 has a plurality of (four in this embodiment) main grooves 1 extending along the tire circumferential direction and a plurality of (this embodiment) partitioned by them. There are five land areas. Among these, the land part (shoulder land part) located in the outermost side of a tire width direction is comprised by the shoulder rib 2 extended continuously in a tire peripheral direction.

  In the present embodiment, a pair of mediate land portions 3 are provided adjacent to the inner side in the tire width direction of the shoulder rib 2, which is composed of a plurality of blocks partitioned by the lateral grooves 5. Moreover, the center land part 4 is provided so that it may pass along the tire equator C, and this is also comprised by the rib. In the present invention, as long as the shoulder land portion is composed of ribs, the structure of the other land portions is not particularly limited.

  The ground contact edge E is the outermost position in the tire axial direction of the ground contact surface that comes into contact with the road surface when a normal load is applied when the tire is placed vertically on a flat road surface with a normal rim assembled and rim assembled on a normal rim. Point to. The regular rim is a standard rim specified in JIS D4202, etc. in principle, and the normal load and the normal internal pressure are the maximum loads specified in JIS D4202 (specifications of automobile tires), etc. ) And the appropriate air pressure.

  As shown in FIGS. 1 and 2, the wall surface of the shoulder rib 2 continuously extends in the tire circumferential direction, and the shoulder rib 2 has a lateral groove having a groove width exceeding 1.5 mm and opening to the main groove 1. Not formed. However, it is conceivable that a sipe having a thickness of 1.5 mm or less (preferably 0.8 mm or less) and opening in the main groove 1 is formed on the shoulder rib 2. It is preferable to terminate without being connected to the groove. Based on this structure, the shoulder rib 2 can ensure good rigidity in the tire front-rear direction.

  The shoulder rib 2 has a narrow groove 6 extending along the tire circumferential direction and closed at both ends, and a cut-out sipe 7 extending outward from the both ends of the narrow groove 6 in the tire width direction. A plurality of them are formed at intervals, so that deterioration of drainage performance due to the rib structure can be suppressed. In addition, since the component extending in the tire width direction is the cut-out sipe 7, a decrease in rigidity in the tire front-rear direction is suppressed, and both ends of the narrow groove 6 are closed, so that a significant increase in the tire width direction is achieved. Reduced rigidity can be avoided.

  The groove width W6 of the narrow groove 6 is larger than the thickness T7 of the sipe 7, preferably 2 to 5 mm, more preferably 3 to 4 mm. When the groove width W6 is 2 mm or more, drainage performance can be effectively secured, and when the groove width W6 is 5 mm or less, a significant reduction in rigidity of the shoulder rib 2 in the tire width direction can be avoided.

  The thickness T7 of the sipe 7 is preferably 0.5 to 1.0 mm, more preferably 0.6 to 0.8 mm. When the thickness T7 is 0.5 mm or more, drainage performance can be effectively secured, and when the thickness T7 is 1.0 mm or less, a significant decrease in rigidity of the shoulder rib 2 in the tire front-rear direction can be avoided. The groove width W6 of the narrow groove 6 and the thickness T7 of the sipe 7 are respectively measured on the tread surface Tr.

  Regarding the shoulder rib 2, the inner side in the tire width direction is defined as the inner rib 21 and the outer side in the tire width direction is defined as the outer rib 22 with respect to the ground contact E. A pattern including a groove or sipe is repeatedly formed in the tire circumferential direction on the inner rib 21, and in the present embodiment, the pattern is constituted by the narrow groove 6 and the sipe 7. The outer rib 22 is formed with a sipe 7 and inclined grooves 8 and short grooves 9 to be described later. The groove area of the shoulder rib 2 is larger in the outer rib 22 than in the inner rib 21. However, the groove area is determined by excluding sipes having a thickness of 1.5 mm or less (preferably 1.0 mm or less) that have a small effect on rigidity.

  The outer rib 22 is formed with a plurality of inclined grooves 8 arranged in the tire circumferential direction and short grooves 9 interposed between the inclined grooves 8. The inclined groove 8 is longer in the tire circumferential direction than the repeated pitch length P of the pattern in the inner rib 21, and both ends are closed in the outer rib 22 and extend obliquely with respect to the tire circumferential direction. The short groove 9 is shorter in the tire circumferential direction than the inclined groove 8, and both end portions are closed within the outer rib 22. The length L8 in the tire circumferential direction of the inclined groove 8 and the length L9 in the tire circumferential direction of the short groove 9 satisfy the relationships of L8> P and L9 <L8, respectively.

  Both ends of the inclined groove 8 are closed within the outer rib 22 as described above, and are not connected to the other groove, the ground contact end E, or the outer end (design end) E2 of the shoulder rib 2 in the tire width direction. The same applies to the short groove 9. However, this is also determined by excluding sipes having a thickness of 1.5 mm or less (preferably 0.8 mm or less) that have a small effect on rigidity, and if such sipes are connected to the inclined grooves 8 and short grooves 9. You may do it.

  In a tire having such a tread surface Tr, the shoulder land portion is constituted by the shoulder rib 2, and the groove area is made larger by the outer rib 22 than the inner rib 21, so ) Good rigidity in the longitudinal direction of the tire can be secured. In addition, a plurality of inclined grooves 8 that are long in the tire circumferential direction are formed in the outer rib 22, and the short grooves 9 are interposed therebetween, and both end portions of each groove are closed in the outer rib 22, so that the shoulder land While maintaining the rigidity of the tire in the longitudinal direction of the tire, it is possible to improve the steering stability performance by appropriately reducing the longitudinal rigidity.

  On the other hand, when the short groove 9 is not formed on the tread surface Tr, the ground pressure in the vicinity of the ground end E increases between the inclined groove 8 and the inclined groove 8 and the grounding property tends to be lowered. Therefore, the effect of improving the steering stability performance cannot be obtained sufficiently. Further, when the inclined groove 8 is provided in place of the short groove 9 and the inclined groove 8 is formed exclusively on the outer rib 22, the longitudinal rigidity of the shoulder rib 2 tends to be excessively lowered. The improvement effect cannot be obtained sufficiently.

  In addition, since the inclined groove 8 and the short groove 9 are in an independent form in which both end portions are closed in this way, there is an advantage that generation of a dent flaw called a bear can be suppressed. The bear is generated when air is trapped between the inner peripheral surface of the vulcanization mold and the outer surface of the tire. If the inclined grooves 8 and the short grooves 9 are independent forms, the projections in the mold for forming them do not form corners, so it becomes easy to suppress air confinement during vulcanization molding and facilitate exhaust, Generation of bears can be prevented well.

  The inclined grooves 8 that are longer in the tire circumferential direction than the repeated pitch length P of the pattern in the inner rib 21 are formed across the pitch, and the longitudinal rigidity of the shoulder rib 2 can be appropriately reduced. In order to enhance this effect, the length L8 of the inclined groove 8 is preferably 1.5 times or more the pitch length P. Further, from the viewpoint of appropriately arranging the short grooves 9, the length L8 of the inclined grooves 8 is preferably not more than twice the pitch length P. Moreover, the length L9 of the short groove 9 is exemplified by a length which is 0.8 times or more and 1.3 times or less of the pitch length P.

  In the present embodiment, an example in which a horizontal U-shaped pattern is configured by the narrow groove 6 and the sipe 7 is shown, but a pattern different from this may be formed on the inner rib 21. Further, the pattern is not limited to having a constant repeat pitch length P, and can be formed using a plurality of types of pitch lengths. When there are a plurality of pitch lengths, the length L8 of the inclined groove 8 only needs to be larger than the longest of them.

  The inclination angle θ of the inclined groove 8 with respect to the tire width direction is preferably in the range of 65 to 85 °. When the inclination angle θ is 65 ° or more, the length L8 of the inclined groove 8 can be set long and the vertical rigidity can be appropriately reduced, and when it is 85 ° or less, the vertical rigidity is prevented from excessively decreasing. be able to.

  The groove width W8 of the inclined groove 8 is preferably in the range of 2 to 4 mm from the viewpoint of appropriately reducing the longitudinal rigidity. The depth of the inclined groove 8 is smaller than the groove width W8, for example, 0.5 to 1.2 mm. Moreover, it is preferable that the groove width W9 (maximum value of the tire width direction distance) of the short groove 9 is 3 mm or more from a viewpoint of reducing longitudinal rigidity moderately, The depth is 0.5-1.2 mm, for example. . The total groove area of the inclined groove 8 and the short groove 9 is preferably 0.15 to 0.25 times the area of the outer rib 22 (the area of the region sandwiched between the ground end E and the outer end E2). .

  On the tread surface Tr, a plurality of inclined grooves 8 are formed at intervals in the tire circumferential direction, and the inclined grooves 8 aligned in the tire circumferential direction are arranged so as not to overlap in the tire width direction. In addition, both end portions of the short groove 9 in the tire circumferential direction are arranged at positions overlapping with the front and rear inclined grooves 8 in the tire circumferential direction in the tire width direction. Accordingly, the inclined grooves 8 and the short grooves 9 can be arranged in a well-balanced manner in the tire circumferential direction, and the longitudinal rigidity of the shoulder rib 2 can be appropriately reduced.

  As shown in FIG. 3, the inclined groove 8 and the short groove 9 are formed in the region A, and are not formed on the inner side in the tire width direction from the region A. This region A is a region that greatly contributes to lowering the longitudinal rigidity of the buttress portion, and is a region from the ground contact end E to the outer end E2 of the shoulder rib 2. By forming the inclined grooves 8 and the short grooves 9 in such a region, it is easy to moderately reduce the longitudinal rigidity while maintaining the rigidity of the shoulder rib 2 in the tire front-rear direction.

  In the present embodiment, an example in which shoulder ribs having such a unique structure are provided on both sides in the tire width direction is shown, but this may be provided only on one side in the tire width direction. In that case, it is preferable to arrange the structure on the outside of the vehicle when the vehicle is mounted in order to improve the steering stability performance. Identification of the mounting direction of the tire with respect to the vehicle is performed, for example, by attaching a display indicating that the vehicle is inside or outside the vehicle to the sidewall portion of the tire.

  Since the internal structure of the pneumatic tire of the present embodiment can be configured in the same manner as a general radial tire, description of the internal structure is omitted. The pneumatic tire of the present invention is the same as a normal pneumatic tire except that the above-described configuration is provided on the tread surface, and conventionally known materials, shapes, structures, manufacturing methods, etc. are all adopted in the present invention. can do.

  Hereinafter, in order to specifically show the configuration and effects of the present invention, the steering stability performance and the occurrence state of bears are evaluated and described. These performance evaluations are performed as follows (1) and (2). The tire size used for the evaluation is 215 / 60R16, and the vehicle is a 2400cc domestic minivan.

(1) Steering stability performance The vehicle specified air pressure was filled and cornered on a dry road surface, and a sensory test was conducted by a driver. The result of Comparative Example 1 is evaluated with an index of 100, and the larger the value, the better the steering stability performance.

(2) Generation status of bear The appearance of the vulcanized tire was observed, and the occurrence status of the bear on the shoulder rib was investigated.

Comparative Example 1
Comparative Example 1 was the same as Example 1 except that the shoulder rib shown in FIG. In the shoulder rib, a lateral groove 18 is formed in the outer rib so as to extend slightly obliquely with respect to the tire width direction and does not reach the outer end E2 in the tire width direction.

Comparative Example 2
Comparative Example 2 was the same as Example 1 except that the shoulder rib shown in FIG. In the shoulder rib, a lateral groove 19 is formed in the outer rib so as to extend slightly obliquely with respect to the tire width direction and reach the outer end E2 in the tire width direction.

Comparative Example 3
In the tread surface shown in FIG. 1, a comparative example 3 is the same as that of Example 1 except that the short groove 9 is not formed.

Example 1
A device having the tread surface shown in FIG.

  In Comparative Examples 1 to 3 and Example 1, the thickness of the sipe 7 formed on the shoulder rib was 0.8 mm. In addition, the tire structure and the rubber composition not specifically described are common. Table 1 shows the evaluation results.

  As shown in Table 1, in Example 1, the steering stability performance is better than those of Comparative Examples 1 to 3, and while maintaining the rigidity of the shoulder rib in the tire front-rear direction, the longitudinal rigidity is moderately lowered and the grounding property is improved. It is thought that the effect is due to the increase. Moreover, in Comparative Example 2, generation of bear was recognized in the vicinity of the outer end of the shoulder rib in the tire width direction.

1 Main groove 2 Shoulder rib 6 Fine groove 7 Sipe 8 Inclined groove 9 Short groove 21 Inner rib 22 Outer rib E Grounding end P Repeat pitch length

Claims (3)

The tread surface is provided with a plurality of land portions defined by a plurality of main grooves extending along the tire circumferential direction, and the land portion located on the outermost side in the tire width direction extends continuously in the tire circumferential direction. In the pneumatic tire composed of ribs,
Regarding the shoulder rib, when the tire width direction inner side is the inner rib and the tire width direction outer side is the outer rib with reference to the ground contact end,
The groove area in the shoulder rib is larger in the outer rib than in the inner rib,
On the inner rib, a pattern including a groove or sipe is repeatedly formed in the tire circumferential direction,
The outer rib is longer in the tire circumferential direction than the repeated pitch length of the pattern in the inner rib, and both ends are closed in the outer rib and extend obliquely with respect to the tire circumferential direction, and are arranged in the tire circumferential direction. A plurality of inclined grooves and a short groove interposed between the inclined grooves, shorter in the tire circumferential direction than the inclined grooves, and closed at both ends within the outer rib. A featured pneumatic tire.   2. The pneumatic tire according to claim 1, wherein a length of the inclined groove in a tire circumferential direction is 1.5 times or more of a repeated pitch length of a pattern in the inner rib.   The inclined grooves arranged in the tire circumferential direction are arranged so as not to overlap in the tire width direction, and both ends of the short groove in the tire circumferential direction are respectively in the tire circumferential direction and the inclined grooves in the tire circumferential direction. The pneumatic tire according to claim 1, wherein the pneumatic tire is disposed at an overlapping position.

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