JP2008273451A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving snow traction performance while maintaining dry performance and wet performance. <P>SOLUTION: The pneumatic tire has an unsymmetrical tread pattern of different groove arrangements on the both sides of the tire equator E. Straight main grooves 2a-2d extending to the tire peripheral direction are arranged on the both sides of the tire equator E. A groove area ratio in a grounded area on the vehicular outside bounded by the tire equator E is made smaller than a groove area ratio in a grounded area on the vehicular inside. In the pneumatic tire, a plurality of projecting parts 3a-3d respectively extending to the tire width direction are provided on groove bottoms of the main grooves 2a-2d while the heights of the projecting parts 3a, 3d in the main grooves 2a, 2d of the vehicular outside are made higher than the heights of the projecting parts 3a, 3b in the main grooves 2a, 2b of the vehicular inside. The number of the projecting parts in the main grooves of the vehicular outside is made larger than that of the projecting parts in the main grooves of the vehicular inside. Further, amplitude of the projecting parts in the main grooves of the vehicular outside is made larger than that of the projecting parts in the main grooves of the vehicular inside. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire having an asymmetric tread pattern, and more particularly to a pneumatic tire capable of improving snow traction performance while maintaining dry performance and wet performance.

  For all-season tires and snow tires, in order to achieve both dry performance and wet performance, the asymmetric tread pattern with different groove arrangement on both sides of the tire equator is adopted, and straights extending in the tire circumferential direction on both sides of the tire equator of the tread part respectively. The groove area ratio in the ground contact area outside the vehicle is made smaller than the groove area ratio in the ground contact area inside the vehicle (for example, patent) Reference 1 and Patent Document 2).

However, when the dry performance and the wet performance are emphasized, the groove component in the tire width direction in the tread portion is inevitably reduced, and it is difficult to sufficiently secure the snow traction performance. On the other hand, if importance is attached to snow traction performance, it becomes difficult to achieve both dry performance and wet performance.
Japanese Patent Laid-Open No. 11-32245 JP 2003-326917 A

  An object of the present invention is to provide a pneumatic tire that can improve snow traction performance while maintaining dry performance and wet performance.

  In order to achieve the above object, the pneumatic tire of the present invention has an asymmetric tread pattern in which the groove arrangement is different on both sides of the tire equator, and straight main grooves extending in the tire circumferential direction on both sides of the tire equator of the tread portion, respectively. A pneumatic tire in which the groove area ratio in the ground contact area outside the vehicle is smaller than the groove area ratio in the ground contact area inside the vehicle with the tire equator as a boundary. A plurality of convex portions extending in the width direction are provided, and the height of the convex portion in the main groove on the vehicle outer side is relatively higher than the height of the convex portion in the main groove on the vehicle inner side. .

  In addition, the pneumatic tire of the present invention for achieving the above object has an asymmetric tread pattern in which the groove arrangement is different on both sides of the tire equator, and each has a straight shape extending in the tire circumferential direction on both sides of the tire equator of the tread portion. In the pneumatic tire in which the main groove is disposed and the groove area ratio in the ground contact area outside the vehicle is smaller than the groove area ratio in the ground contact area inside the vehicle at the tire equator, A plurality of convex portions each extending in the tire width direction are provided, and the number of convex portions in the main groove on the vehicle outer side is relatively larger than the number of convex portions in the main groove on the vehicle inner side. is there.

  Furthermore, the pneumatic tire of the present invention for achieving the above object has an asymmetric tread pattern in which the groove arrangement is different on both sides of the tire equator, and has a straight shape extending in the tire circumferential direction on both sides of the tire equator of the tread portion. In the pneumatic tire in which the main groove is disposed and the groove area ratio in the ground contact area outside the vehicle is smaller than the groove area ratio in the ground contact area inside the vehicle at the tire equator, Providing a plurality of convex portions each extending in the tire width direction and having a corrugated shape, the amplitude of the convex portion in the main groove on the vehicle outer side is made relatively larger than the amplitude of the convex portion in the main groove on the vehicle inner side. It is a feature.

  In the present invention, in the pneumatic tire having the asymmetric tread pattern as described above, a plurality of convex portions extending in the tire width direction are formed at the groove bottom of the main groove. These projections contribute to improving the snow traction performance by scratching the snow that has entered the main groove when running on the snow surface. However, when the convex portions are provided uniformly with respect to the main groove on the vehicle inner side and the main groove on the vehicle outer side, the drainage performance in the ground contact area inside the vehicle with the increased groove area ratio is hindered and the wet performance is reduced. It will be. Therefore, the snow traction performance is improved while maintaining the wet performance by making the edge effect by the convex portion provided in the main groove outside the vehicle relatively larger than the edge effect of the convex portion provided in the main groove inside the vehicle. Is possible. Of course, the convex part formed in the groove bottom of the main groove does not impair the dry performance.

  When the height of the convex portion in the main groove on the vehicle outer side is relatively higher than the height of the convex portion in the main groove on the vehicle inner side, the height of the convex portion in the main groove on the vehicle inner side is 0.3 mm or more and the main groove It is preferable that the depth is 20% or less, and the height of the convex portion in the main groove outside the vehicle is 30% or less of the main groove depth. Thereby, the wet performance can be sufficiently maintained when the snow traction performance is improved. Further, when the pitch of the land element in the tread portion is changed in the tire circumferential direction, the height of the convex part adjacent to the large pitch land element is adjacent to the small pitch land element in the same main groove. It is preferable to make the height of the convex portion relatively higher. Thus, the improvement effect of snow traction performance can be enhanced by increasing the edge effect by relatively increasing the convexity adjacent to the land element having a large pitch and high rigidity.

  When the number of protrusions in the main groove outside the vehicle is relatively larger than the number of protrusions in the main groove inside the vehicle, the number of protrusions in the main groove outside the vehicle is The number is preferably 1.3 to 2.0 times the number. Thereby, snow traction performance and wet performance can be improved with good balance. Further, when the pitch of the land element in the tread portion is changed in the tire circumferential direction, the height of the convex part adjacent to the large pitch land element is adjacent to the small pitch land element in the same main groove. It is preferable to make the height of the convex portion relatively higher. Thus, the improvement effect of snow traction performance can be enhanced by increasing the edge effect by relatively increasing the convexity adjacent to the land element having a large pitch and high rigidity.

  When the convex portion provided in the main groove has a corrugated shape and the amplitude of the convex portion in the main groove outside the vehicle is relatively larger than the amplitude of the convex portion in the main groove inside the vehicle, The amplitude is preferably 1.2 to 2.0 times the amplitude of the convex portion in the main groove inside the vehicle. Thereby, snow traction performance and wet performance can be improved with good balance. Further, when the pitch of the land element in the tread is changed in the tire circumferential direction, the amplitude of the convex part adjacent to the large pitch land element in the same main groove is changed to the convex part adjacent to the small pitch land element. It is preferable to make the amplitude of the portion relatively larger. Thus, the effect of improving snow traction performance can be enhanced by increasing the edge effect by relatively increasing the amplitude of the convex portion adjacent to the land element having a large pitch and high rigidity.

  Note that the above three methods for adjusting the edge effect due to the convex portions can be used alone, but may be used in combination. By combining these, it becomes possible to further improve the snow traction performance.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a tread pattern of a pneumatic tire according to an embodiment of the present invention. In FIG. 1, IN is the inside of the vehicle when the vehicle is mounted, and OUT is the outside of the vehicle when the vehicle is mounted. FIG. 2 is a cross-sectional view showing a tread portion of the pneumatic tire of FIG. However, in FIG. 2, a part of the groove is omitted.

  As shown in FIG. 1, the tread portion 1 is formed with four main grooves 2a to 2d extending straight in the tire circumferential direction, and these main grooves 2a to 2d form five rows from the vehicle inner side toward the outer side. Land portions 10, 20, 30, 40, and 50 are divided. The main grooves 2a to 2d have a groove depth of 8.0 mm to 9.0 mm and a groove width of 10 mm to 12 mm.

  A narrow groove 11 extending in the tire circumferential direction, a plurality of lug grooves 12 extending in the tire width direction and dividing the land portion 10 into a block shape, and the lug grooves 12 between the land portions 10 located on the innermost side of the vehicle. Are formed with a plurality of narrow grooves 13 extending in the tire width direction. A plurality of curved grooves 21 that are curved while being inclined with respect to the tire circumferential direction are formed in the land portion 20. The land portion 30 includes a quasi-main groove 31 extending in the tire circumferential direction, a plurality of inclined grooves 32 that are inclined with respect to the tire circumferential direction, and a plurality of curved grooves 33 that are curved while being inclined with respect to the tire circumferential direction. Is formed. The inclined groove 32 is located on the vehicle inner side than the semi-main groove 31, and the curved groove 33 is located on the vehicle outer side than the semi-main groove 31. The land portion 40 is formed with a shallow groove 41 extending in the tire circumferential direction and a plurality of inclined grooves 42 positioned on both sides of the shallow groove 41 while being inclined in the tire circumferential direction. The land portion 50 located on the outermost side of the vehicle has a narrow groove 51 extending in the tire circumferential direction, a plurality of lug grooves 52 extending in the tire width direction and dividing the land portion 50 into blocks, and the lug grooves 52 between each other. Are formed with a plurality of narrow grooves 53 extending in the tire width direction.

  The pneumatic tire of the present embodiment has asymmetric tread patterns with different groove arrangements on both sides of the tire equator E, and has straight main grooves 2a to 2d extending in the tire circumferential direction on both sides of the tire equator E of the tread portion 1. I have. In the asymmetric tread pattern, the groove area ratio in the ground contact area outside the vehicle is smaller than the groove area ratio in the ground contact area inside the vehicle with the tire equator E as a boundary. In addition, what is necessary is just to set the groove area ratio in the whole tread to 25%-45%. The contact area is filled with the air pressure corresponding to the maximum load capacity specified by the standard on which the tire is based (JATMA, ETRTO or TRA), and within the contact width TCW when a load of 80% of the maximum load capacity is applied. It is an area.

  In the pneumatic tire, a plurality of convex portions 3a to 3d extending in the tire width direction are formed at the groove bottoms of the main grooves 2a to 2d, respectively. The convex portions 3a to 3d have a thickness of 1 mm to 3 mm, for example, and are arranged at intervals in the tire circumferential direction. These convex portions 3a to 3d scrape the snow that has entered the main groove when running on the snow surface and contribute to improving the snow traction performance. However, the main grooves 2a and 2b on the vehicle inner side and the main grooves 2c on the outer side of the vehicle, When the convex portions are uniformly provided with respect to 2d, the drainage performance in the ground contact area inside the vehicle with the increased groove area ratio is hindered, and the wet performance is deteriorated. Therefore, the edge effect by the convex portions 3c, 3d provided in the main grooves 2c, 2d outside the vehicle is relatively larger than the edge effect of the convex portions 3a, 3b provided in the main grooves 2a, 2b inside the vehicle by a method described later. This improves snow traction performance while maintaining wet performance.

  As a first technique, as shown in FIG. 2, the heights Hc, Hd of the convex portions 3c, 3d in the main grooves 2c, 2d on the vehicle outer side are set to the heights of the convex portions 3a, 3b in the main grooves 2a, 2b on the vehicle inner side. It is relatively higher than Ha and Hb. Thereby, snow traction performance can be improved while maintaining wet performance.

  In this case, the heights Ha and Hb of the convex portions 3a and 3b in the main grooves 2a and 2b on the vehicle inner side are 0.3 mm or more and 20% or less of the main groove depths Da and Db, and the main grooves 2c and 2d on the vehicle outer side are set. The heights Hc and Hd of the protrusions 3c and 3d at the height are preferably 30% or less of the main groove depths Dc and Dd. The main groove depths Da to Dd are constant. If the heights Ha and Hb are less than 0.3 mm, the effect of improving the snow traction performance becomes insufficient, the heights Ha and Hb exceed 20% of the main groove depths Da and Db, or the height Hc. , Hd exceeds 30% of the main groove depths Dc, Dd, the wet performance deteriorates.

  The heights Ha to Hd of the convex portions 3a to 3d are basically constant in the same main groove. However, the heights Ha to Hd of the convex portions 3a to 3d may be varied in the same main groove according to so-called pitch variations.

  That is, when changing the pitch of the land element of the tread portion 1 in the tire circumferential direction, the height of the convex part adjacent to the large pitch land element in the same main groove is set to the convex part adjacent to the small pitch land element. The height of the part can be made relatively higher. For example, FIG. 3 shows the convex portion 3d formed on the groove bottom of the main groove 2d located on the outermost side of the vehicle and the land portion 50 adjacent thereto, but the pitches P1, P2 of the land portion 50 are P1 <P2. When the relationship is satisfied, the heights Hd1 and Hd2 of the convex portions 3d corresponding thereto are set to Hd1 <Hd2. Thus, the improvement effect of snow traction performance can be enhanced by increasing the edge effect by relatively increasing the convexity adjacent to the land element having a large pitch and high rigidity. Even in this case, it is assumed that the relationship of Ha, Hb <Hc, Hd is satisfied at the same position in the tire circumferential direction.

  As a second method, as shown in FIG. 1, the number of the convex portions 3c, 3d in the main grooves 2c, 2d on the vehicle outer side is relative to the number of the convex portions 3a, 3b in the main grooves 2a, 2b on the vehicle inner side. To more. Thereby, snow traction performance can be improved while maintaining wet performance.

  In this case, the number of the convex portions 3c, 3d in the main grooves 2c, 2d on the vehicle outer side is preferably 1.3 to 2.0 times the number of the convex portions 3a, 3b in the main grooves 2a, 2b on the vehicle inner side. When this magnification is out of the above range, the effect of achieving both snow traction performance and wet performance becomes insufficient. Similarly to the above, when the pitch of the land element of the tread portion 1 is changed in the tire circumferential direction, the height of the convex part adjacent to the large pitch land element in the same main groove is set to a small pitch. You may make the height of the convex part adjacent to a land part element relatively higher.

  As a third method, the convex portions 3a to 3d provided in the main grooves 2a to 2d are formed in a corrugated shape, and the amplitude of the convex portions 3c and 3d in the main grooves 2c and 2d on the vehicle outer side is set to be convex in the main grooves 2a and 2b on the vehicle inner side. It is relatively larger than the amplitude of the parts 3a and 3b. For example, FIG. 4 shows the convex portion 3a in the main groove 2a located on the innermost side of the vehicle and the convex portion 3d in the main groove 2d located on the outermost side of the vehicle side by side, and the amplitude Td of the convex portion 3d is shown as the convex portion 3a. Is larger than the amplitude Ta. Thereby, snow traction performance can be improved while maintaining wet performance.

  In this case, the amplitude of the convex portions 3c and 3d in the main grooves 2c and 2d on the vehicle outer side is preferably 1.2 to 2.0 times the amplitude of the convex portions 3a and 3b in the main grooves 2a and 2b on the vehicle inner side. When this magnification is out of the above range, the effect of achieving both snow traction performance and wet performance becomes insufficient.

  Further, when the pitch of the land element of the tread portion 1 is changed in the tire circumferential direction, the amplitude of the convex portion adjacent to the large pitch land element is adjacent to the small pitch land element in the same main groove. The amplitude of the convex portion can be made relatively larger. For example, FIG. 5 shows the convex portion 3d formed on the groove bottom of the main groove 2d located on the outermost side of the vehicle and the land portion 50 adjacent thereto, but the pitches P1, P2 of the land portion 50 are P1 <P2. When the relationship is satisfied, the amplitudes Td1 and Td2 of the convex portion 3d corresponding thereto are set to Td1 <Td2. Thus, the effect of improving snow traction performance can be enhanced by increasing the edge effect by relatively increasing the amplitude of the convex portion adjacent to the land element having a large pitch and high rigidity. Even in this case, the amplitudes Ta, Tb, Tc, Td of the convex portions 3a, 3b, 3c, 3d are assumed to satisfy the relationship of Ta, Tb <Tc, Td at the same position in the tire circumferential direction.

  The tire size 295 / 40R21 has an asymmetric tread pattern with different groove arrangements on both sides of the tire equator, straight main grooves extending in the tire circumferential direction are arranged on both sides of the tire equator of the tread portion, and the tire equator In a pneumatic tire (see FIG. 1) in which the groove area ratio in the ground contact area outside the vehicle is smaller than the groove area ratio in the ground contact area inside the vehicle, each extends in the tire width direction at the groove bottom of the main groove. A tire of Example 1 was produced in which a plurality of convex portions were provided at equal intervals, and the height of the convex portions in the main groove on the vehicle outer side was relatively higher than the height of the convex portions in the main groove on the vehicle inner side. In Example 1, the height of the convex portion in the main groove inside the vehicle was 1.0 mm, and the height of the convex portion in the main groove outside the vehicle was 2.0 mm. The number of convex portions in each main groove was 120. The depth of the main groove is 7.5 mm.

  Further, the tire of Example 2 having the same configuration as that of Example 1 except that the number of convex portions in the main groove inside the vehicle is 120 and the number of convex portions in the main groove outside the vehicle is 240 is manufactured. did.

  In addition, the projecting portion provided in each main groove has a corrugated shape, the amplitude of the projecting portion in the main groove inside the vehicle is 1.2 mm, and the amplitude of the projecting portion in the main groove outside the vehicle is 1.5 mm. A tire of Example 3 having the same configuration as Example 2 was produced.

  For comparison, a tire of Comparative Example 1 having the same configuration as that of Example 1 was prepared except that the height of all the convex portions was set to 1 mm.

  These tires were evaluated for snow traction performance and wet performance by the following evaluation methods, and the results are shown in Table 1.

Snow traction performance:
The test tire was mounted on a four-wheel drive vehicle, the air pressure was 240 kPa, and the reactivity at the time of starting on snow was evaluated. The evaluation results are shown as an index with Comparative Example 1 as 100. A larger index value means better snow traction performance.

Wet performance:
The test tire was mounted on a four-wheel drive vehicle, and the turning performance on a wet road surface was evaluated with a feeling of air pressure of 240 kPa. The evaluation results are shown as an index with Comparative Example 1 as 100. The larger the index value, the better the wet performance.

  As is apparent from Table 1, the tires of Examples 1 to 3 were able to demonstrate good snow traction performance while maintaining the wet performance equivalent to that of Comparative Example 1.

  Next, the convex portion provided in each main groove has a corrugated shape, the amplitude of the convex portion adjacent to the large pitch land element in the same main groove is 1.5 mm, and the small pitch land element in the same main groove. A tire of Example 4 having the same configuration as that of Example 2 was produced, except that the amplitude of the convex portion adjacent to was set to 1.2 mm. When the tire was evaluated in the same manner as described above, the evaluation value of the wet performance was 100, and the evaluation value of the snow traction performance was 110.

  Next, in the main groove inside the vehicle, the height of the convex portion adjacent to the small pitch land element is 0.5 mm, the height of the convex portion adjacent to the large pitch land element is 1.0 mm, In the main groove outside the vehicle, the height of the convex portion adjacent to the small pitch land element is 1.5 mm, and the height of the convex portion adjacent to the large pitch land element is 2.0 mm. A tire of Example 5 having the same configuration as that of Example 2 was produced. When the tire was evaluated in the same manner as described above, the evaluation value of the wet performance was 100, and the evaluation value of the snow traction performance was 110.

It is an expanded view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. It is sectional drawing which shows the tread part of the pneumatic tire of FIG. It is a side view which shows the convex part formed in the groove bottom of the main groove located in the outermost vehicle side, and the land part adjacent to it. FIG. 4 is a plan view showing a convex portion in a main groove located on the innermost side of the vehicle and a convex portion in the main groove located on the outermost side of the vehicle side by side. It is a top view which shows the convex part formed in the groove bottom of the main groove located in the vehicle outermost side, and the land part adjacent to it.

Explanation of symbols

1 tread portion 2a to 2d main groove 3a to 3d convex portion 10, 20, 30, 40, 50 land portion

Claims (9)

  Asymmetric tread pattern with different groove arrangement on both sides of the tire equator, straight main grooves extending in the tire circumferential direction are arranged on both sides of the tire equator in the tread part, and grounding outside the vehicle with the tire equator as a boundary In the pneumatic tire in which the groove area ratio in the region is smaller than the groove area ratio in the ground contact area inside the vehicle, a plurality of protrusions extending in the tire width direction are provided on the groove bottom of the main groove, and the vehicle outer side A pneumatic tire in which the height of the convex portion in the main groove is relatively higher than the height of the convex portion in the main groove inside the vehicle.   The height of the convex portion in the main groove inside the vehicle is 0.3 mm or more and 20% or less of the main groove depth, and the height of the convex portion in the main groove outside the vehicle is 30% or less of the main groove depth. Item 2. The pneumatic tire according to Item 1.   When the pitch of the land element of the tread portion is changed in the tire circumferential direction, the height of the convex part adjacent to the large pitch land element is set to the convex part adjacent to the small pitch land element in the same main groove. The pneumatic tire according to claim 1, wherein the height of the portion is relatively higher.   Asymmetric tread pattern with different groove arrangement on both sides of the tire equator, straight main grooves extending in the tire circumferential direction are arranged on both sides of the tire equator in the tread part, and grounding outside the vehicle with the tire equator as a boundary In the pneumatic tire in which the groove area ratio in the region is smaller than the groove area ratio in the ground contact area inside the vehicle, a plurality of protrusions extending in the tire width direction are provided on the groove bottom of the main groove, and the vehicle outer side A pneumatic tire in which the number of protrusions in the main groove is relatively greater than the number of protrusions in the main groove inside the vehicle.   The pneumatic tire according to claim 4, wherein the number of protrusions in the main groove on the vehicle outer side is 1.3 to 2.0 times the number of protrusions in the main groove on the vehicle inner side.   When the pitch of the land element of the tread portion is changed in the tire circumferential direction, the height of the convex part adjacent to the large pitch land element is set to the convex part adjacent to the small pitch land element in the same main groove. The pneumatic tire according to claim 4, wherein the height of the portion is relatively higher.   Asymmetric tread pattern with different groove arrangement on both sides of the tire equator, straight main grooves extending in the tire circumferential direction are arranged on both sides of the tire equator in the tread part, and grounding outside the vehicle with the tire equator as a boundary In the pneumatic tire in which the groove area ratio in the region is smaller than the groove area ratio in the ground contact area inside the vehicle, a plurality of convex portions each having a corrugated shape extending in the tire width direction are provided at the groove bottom of the main groove. A pneumatic tire provided with the amplitude of the convex portion in the main groove on the vehicle outer side relatively larger than the amplitude of the convex portion in the main groove on the vehicle inner side.   The pneumatic tire according to claim 7, wherein the amplitude of the convex portion in the main groove outside the vehicle is 1.2 to 2.0 times the amplitude of the convex portion in the main groove inside the vehicle.   When the pitch of the land element of the tread portion is changed in the tire circumferential direction, the amplitude of the convex part adjacent to the large pitch land element in the same main groove is the convex part adjacent to the small pitch land element. The pneumatic tire according to claim 4, wherein the amplitude of is relatively larger.

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