JP2008260356A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire, which can compatibly achieve steering stability on a snow road surface and steering stability on a dry road surface, and is excellent in uneven abrasion-resistance. <P>SOLUTION: A land part only comprising a block is arranged at an in-side area Ai becoming an inner side at vehicle attachment of a tread surface formed with a plurality of main grooves 1-5, and a land part including a rib is arranged at an outer side area Ao becoming an outer side at vehicle attachment. Further, groove areas of the main grooves 1-5 are larger at the outer side area Ao than the in-side area Ai, and the groove areas of the lateral grooves 6-9 are larger at the inner side area Ai than the outer side area Ao. Difference of a void ratio of the inner side area Ai and the outer side area Ao is made to 5% or less, and a mutual area ratio of the respective land parts arranged on center areas Ci, CO, mediate areas Mi, Mo, and shoulder areas Si, So is set to 1.4 or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire with improved maneuverability on a snow road surface, and is particularly useful as a winter tire.

  Usually, various tread patterns corresponding to required tire performance and use conditions are formed on the tread surface of a pneumatic tire. In particular, in winter tires used for running on snowy roads, it is common to place blocks on the entire surface of the tread surface, thereby improving the maneuverability (steering stability) on the snowy road surface. ing. By the way, in recent winter tires, there is a tendency that not only the maneuverability on the snow road surface but also the maneuverability on the dry road surface is emphasized, and there is a strong demand for a tire that can sufficiently meet such demands. Yes.

On the other hand, in Patent Document 1 below, only the block is disposed in the in-side region that is the inner side when the tread surface is mounted on the vehicle, and the rib is disposed in the outer side region that is the outer side when the vehicle is mounted. A pneumatic tire is described in which the void ratio of the side region and the out side region is within a predetermined range, and the void ratio is increased by 5% or more in the in side region than in the out side region. However, in this tire, since the void ratio is greatly different between the in-side region and the out-side region, there is a problem that the contact pressure tends to be non-uniform and uneven wear tends to occur on the tread surface. In particular, in winter tires in which the tread rubber is softer than summer tires and the like, uneven wear due to uneven grounding is remarkable, and it is very important to improve this in practice.
JP-A-11-342706

  The present invention has been made in view of the above circumstances, and the purpose thereof is a pneumatic that can achieve both the handling on a snow road and the handling on a dry road, and also has excellent uneven wear resistance. To provide tires.

  The pneumatic tire according to the present invention is a center region disposed in the vicinity of the tire equator by a plurality of main grooves extending in the tire circumferential direction, and a mediate region disposed outside the center region, A tread surface that is divided into a shoulder region disposed outside the mediate region, and the main groove and the tread surface in an inward region that is the inner side when the vehicle is mounted with respect to the tire equator A land portion including only blocks separated by a transverse groove intersecting the main groove, and a land including a rib extending in the tire circumferential direction on the outer side when the vehicle is mounted with respect to the tire equator. A groove area of the main groove is larger in the out side region than the in side region, and a groove area of the lateral groove is larger in the in side region than the out side region, and the in side region and the Au The difference in the void ratio with the side area is within 5%, and the area ratio of each land portion arranged in the center area, the mediate area and the shoulder area is 1.4 or less. is there.

  In the pneumatic tire according to the present invention, the groove area of the lateral groove extending across the tire circumferential direction while improving the turning traction on the snow road surface by increasing the groove area of the main groove extending in the tire circumferential direction in the out-side region. Since the in-side region is large, the front and rear traction on the snow road surface can be improved, so that excellent maneuverability can be exhibited on the snow road surface. In addition, by providing ribs having higher rigidity than the block in the out side region, which has a large effect during turning, the operability on the dry road surface can be improved. In addition, the difference in void ratio between the in-side region and the out-side region is suppressed to within 5%, and the substantial ground contact area of both regions is made substantially equal. Abrasion can be improved, and furthermore, since the mutual area ratio of each land portion arranged in the center region, the mediate region and the shoulder region is set to 1.4 or less, in each land portion It is possible to suppress local uneven wear. Here, the void ratio is the ratio (%) of the groove area to the ground contact area, and can be calculated by the equation {1−actual ground contact area (land area) / ground area (land area + groove area)} × 100. .

  As described above, the pneumatic tire according to the present invention has different land shape and groove area between the in-side region and the out-side region in order to improve the maneuverability on the snow road surface and the dry road surface. The tread pattern is asymmetric with respect to the tire equator. In such an asymmetric pattern, as described above, the void ratio between the in-side region and the out-side region is substantially equal, and the mutual area ratio of each land portion is set to a predetermined value or less, thereby making the contact pressure uniformity. It is what raises. As a result, it is possible to exhibit excellent uneven wear resistance while achieving both the maneuverability on the snow road surface and the maneuverability on the dry road surface.

  In the above, the void ratio of the in-side region is 35 ± 5%, the void ratio relating to the main groove therein is 10 ± 10%, and the void ratio relating to the lateral groove is 25 ± 10%, It is preferable that the void ratio of the region is 35 ± 5%, the void ratio relating to the main groove therein is 25 ± 5%, and the void ratio relating to the lateral groove is 10 ± 5%.

  According to such a configuration, when setting the void ratio between the in-side region and the out-side region as described above, by setting the void ratios of both regions within a range of 35 ± 5%, the wear life, drainage, etc. The effects of the present invention described above can be suitably achieved while suppressing the effect on tire performance. Furthermore, in this case, by ensuring the groove area of the main groove in the out-side region and the groove area of the lateral groove in the in-side region with a void ratio of around 25%, respectively, the turning traction and the front and rear traction on the snow road surface are achieved. It is possible to improve appropriately and to effectively improve the maneuverability on the snow road surface.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a development view showing an example of a tread surface of a pneumatic tire according to the present invention. This pneumatic tire has an asymmetric pattern formed on the tread surface with respect to the tire equator CL, and is directed to the vehicle so that the right side in FIG. 1 is on the inside of the vehicle and the left side in FIG. 1 is on the outside of the vehicle. Accordingly, the in-side area Ai is an area that is on the inner side when the vehicle is mounted with reference to the tire equator CL, and the out-side area Ao is an area that is on the outer side when the vehicle is mounted with reference to the tire equator CL.

  The ground contact end E, which is the outer end of the in-side region Ai and the out-side region Ao, is the outermost position in the tire axial direction where the tire is placed perpendicular to the plane in a state in which the normal internal pressure is filled and the normal load is applied. Is defined as The normal load and the normal internal pressure are the maximum load (design normal load in the case of passenger car tires) defined in JIS D4202 and the air pressure corresponding thereto.

  The tread surface is provided with five main grooves 1 to 5 that extend continuously in the tire circumferential direction in a straight shape, and lateral grooves 6 to 9 that extend so as to intersect with them. The tread surface includes, by main grooves 1 to 5, center areas Ci and Co arranged in the vicinity of the tire equator CL, mediate areas Mi and Mo arranged outside the center areas Ci and Co, and The area is divided into six areas including shoulder areas Si and So arranged outside the mediate areas Mi and Mo. Here, when the distance in the tire width direction from the tire equator CL to the ground contact edge E is the ground contact half width W, the width dimension of the center areas Ci and Co (the tire width direction from the tire equator CL to the center line of the main grooves 2 and 4) Examples of the ratio of the distance) to the ground half width W are 24.8 to 35.0%. Further, the ratio of the width dimension of the shoulder areas Si and So (the distance in the tire width direction from the ground contact edge E to the center line of the main grooves 1 and 5) to the ground contact half width W is 29.4 to 42.4%. Illustrated.

  As shown in FIG. 1, in the in-side area Ai of the tread surface, a land portion composed only of blocks divided at a predetermined pitch by the main grooves 3 to 5 and the lateral grooves 7 to 9 is arranged. The lateral grooves 7 and 8 extend while inclining in the tire circumferential direction, and the blocks arranged in the center area Ci and the mediate area Mi have a rhombus in plan view. On the other hand, a land portion including ribs divided by the main grooves 1 to 3 is arranged in the out-side region Ao. As described above, the ribs having a relatively high rigidity are arranged in the out-side area Ao that has a large effect during turning, thereby improving the operability on the dry road surface.

  The tread surface of this pneumatic tire is formed such that the groove area of the main groove is larger in the out-side area Ao than the in-side area Ai, and the groove area of the lateral groove is larger in the in-side area Ai than the out-side area Ao. ing. That is, the groove area of the main grooves 1 to 3 in the out side region Ao (half of the main groove 3) is more than the groove area of the main grooves 3 to 5 in the in side region Ai (half of the main groove 3). The groove area of the lateral grooves 7 to 9 in the in-side region Ai is larger than the groove area of the lateral grooves 6 in the out-side region Ao. Thereby, the turning traction and the front and rear traction on the snow road surface can be improved, and the maneuverability on the snow road surface can be improved.

The void ratio Vo (m) of the main grooves 1 to 3 in the out-side region Ao is set to increase the void ratio Vi ( It is preferably 5% or more larger than m), more preferably 10% or more. Further, the void ratio Vi (l) of the lateral grooves 7 to 9 in the in-side region Ai is preferably 5% or more, preferably 10% or more larger than the void ratio Vo (l) of the lateral grooves 6 in the out-side region Ao. Is more preferable. In this embodiment, these void ratios can be calculated by the following formula.
Void ratio Vo (m): groove area of main grooves 1 to 3 (half of main groove 3) / ground area of out-side area Ao × 100
Void ratio Vi (m): groove area of main grooves 3 to 5 (half of main groove 3) / ground area of in-side region Ai × 100
Void ratio Vi (l): groove area of lateral grooves 7-9 / ground area of in-side area Ai × 100
Void ratio Vo (l): groove area of lateral groove 6 / ground area of out-side area Ao × 100

The tread surface is formed so that the difference between the void ratio Vi of the in-side region Ai and the void ratio Vo of the out-side region Ao is within 5%. The difference in void ratio is preferably less than 5%, more preferably within 3%. In this embodiment, these void ratios can be calculated by the following formula.
Void ratio Vi: Groove area of main grooves 3-5 and lateral grooves 7-9 (half of main groove 3) / ground area of in-side region Ai × 100
Void ratio Vo: groove area of main grooves 1 to 3 and lateral groove 6 (half of main groove 3) / ground area of out-side region Ao × 100

  Further, the tread surface is formed so that the mutual area ratio of each land portion arranged in the center areas Ci, Co, the mediate areas Mi, Mo and the shoulder areas Si, So is 1.4 or less. . The maximum area ratio is the ratio of the smallest area to the largest land area in the six areas, and the maximum area ratio may be 1.4 or less. This area ratio is preferably 1.2 or less, and more preferably 1.0 or less.

  In this pneumatic tire, as described above, the difference in void ratio between the in-side region Ai and the out-side region Ao is suppressed to within 5%, and the substantial ground contact area of both regions is made substantially equal. Uneven wear resistance can be improved by improving the uniformity of the contact pressure. Furthermore, the mutual areas of the land portions arranged in the center areas Ci, Co, the mediate areas Mi, Mo and the shoulder areas Si, So. Since the ratio is suppressed to 1.4 or less, local uneven wear in each land portion can be suppressed. As a result, it is possible to exhibit excellent uneven wear resistance while achieving both the maneuverability on the snow road surface and the maneuverability on the dry road surface.

  In the present invention, the void ratio Vi of the in-side region Ai is 35 ± 5%, the void ratio Vi (m) relating to the main grooves 3 to 5 is 10 ± 10%, and the void ratio Vi relating to the lateral grooves 7 to 9 is included. (L) is 25 ± 10%, the void ratio Vo of the out-side region Ao is 35 ± 5%, and the void ratio Vo (m) for the main grooves 1 to 3 is 25 ± 5%, and the lateral groove Preferably, the void ratio Vo (l) for 6 is 10 ± 5%. Thereby, while suppressing the influence on other tire performances such as wear life and drainage performance, the above-described operational effects of the present invention can be suitably achieved, and the turning traction and the front and rear traction on the snow road surface are appropriately improved. Thus, the maneuverability on the snow road surface can be effectively enhanced. About the dimension for setting such a void ratio, what is shown in the below-mentioned Example can be illustrated.

  The pneumatic tire of the present invention is useful as a studless tire (winter tire). In winter tires, a relatively soft tread rubber having a rubber hardness measured in accordance with the JISK6253 durometer hardness test (type A) of about 45 to 65 °, particularly about 45 to 55 ° in Japan, is adopted. The occurrence of uneven wear due to uneven grounding is remarkable, but according to the present invention, as described above, the uniformity of the contact pressure is improved while ensuring the operability on the snow road surface and the dry road surface. Abrasion can be improved.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that the tread surface is configured as described above, and any conventionally known material, shape, structure, manufacturing method, etc. are adopted in the present invention. be able to.

  The tread pattern of the pneumatic tire according to the present invention is not limited to that shown in the above-described embodiment. Accordingly, the main groove may extend in a zigzag shape along the tire circumferential direction, or the block or rib may be provided with a closing slit or a notch. In order to enhance the function as a winter tire, sipes may be provided on the blocks and ribs, but the sipes are not considered as groove areas. Further, in the above-described embodiment, an example in which the tread surface is divided into six areas by five main grooves is shown, but in the present invention, the center area is made single without providing the main grooves near the tire equator, The tread surface may be divided into five areas by four main grooves. Even in such a case, the form of the land portion, the void ratio, and the mutual area ratio of each land portion are set so as not to depart from the above-described range.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, each performance evaluation of the tire was performed as follows.

(1) Snow handling performance Test tires are mounted on all wheels of a real car (2000cc 4WD sedan car, 2 passengers), run on a snowy road with air pressure of 210kPa, and go straight, turn, brake, etc. It was evaluated by. The evaluation is made out of 10 points, and the larger the value, the better the snow maneuverability.

(2) Dry operability A dry road surface was run under the same conditions as in (1) above, and evaluated by a sensory test. The evaluation is made out of 10 points, and the larger the value, the better the dry operability.

(3) Uneven wear resistance After wearing test tires on all wheels of a real car (2000cc 4WD sedan car, 2 passengers) and running on a general road at an air pressure of 210 kPa for 12,000 km, the wear amount depends on the depth of each main groove. Was measured, and the ratio of wear amount (maximum value / minimum value) was calculated as the uneven wear ratio and the wear form was observed. The closer to 1.0 this uneven wear ratio is, the more uniform wear is, indicating that the uneven wear resistance is excellent.

Comparative Examples 1-4, Examples 1 and 2
In the tread surface shown in FIG. 1, the ground contact half width W is 80 mm, 1 pitch (FIG. 1 shows 2 pitches) tire circumferential direction length is 30 mm, main groove widths W1 to W5, land area, etc. The dimensions were set as shown in Table 1 to give Comparative Examples 1 to 4 and Examples 1 and 2. The lateral groove width is set so that the main groove width and land area shown in Table 1 are obtained, the tire size is 205 / 55R16, and the rim size is 16 × 6.5J. The evaluation results are shown in Table 2.

  As shown in Table 2, in Comparative Examples 1 and 2, the difference in the void ratio between the in-side region and the out-side region is large, and the ground pressure in the in-side region tends to be higher than the out-side region. Uneven wear occurs in a form in which the in-side region wears early. Moreover, in Comparative Examples 3 and 4, since the mutual area ratio of each land portion is large, local uneven wear occurs such that the center region and shoulder regions on both sides are worn early. On the other hand, in Examples 1 and 2, the tread surface is worn relatively evenly while achieving both the maneuverability on the snow road surface and the maneuverability on the dry road surface. It turns out that it is excellent in.

The expanded view which shows an example of the tread surface of the pneumatic tire which concerns on this invention

Explanation of symbols

1-5 Main groove 6-9 Horizontal groove Ai Inner side area Ao Outer side area Ci Center area Co Center area CL Tire equator E Grounding edge Mi Mediate area Mo Mediate area Si Shoulder area So Shoulder area

Claims (2)

A plurality of main grooves extending in the tire circumferential direction are arranged at the center area disposed near the tire equator, the mediate area disposed outside the center area, and the outside of the mediate area. Has a tread surface that is divided into a shoulder area,
A land portion consisting only of blocks divided by the main groove and a transverse groove intersecting the main groove is arranged in the in-side region which is the inner side when the vehicle is mounted with respect to the tire equator on the tread surface, A land portion including ribs extending in the tire circumferential direction is arranged in the outer side region which is the outer side when the vehicle is mounted with respect to the tire equator,
A groove area of the main groove is larger in the out side region than the in side region, a groove area of the lateral groove is larger in the in side region than the out side region, and the in side region and the out side region A pneumatic tire in which a difference in void ratio is within 5%, and an area ratio between the land portions arranged in the center area, the mediate area, and the shoulder area is 1.4 or less. The void ratio of the in-side region is 35 ± 5%, the void ratio relating to the main groove therein is 10 ± 10%, and the void ratio relating to the lateral groove is 25 ± 10%,
2. The pneumatic system according to claim 1, wherein a void ratio in the out-side region is 35 ± 5%, a void ratio in the main groove is 25 ± 5%, and a void ratio in the lateral groove is 10 ± 5%. tire.

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